The Al-Mg 5xxx series aluminum alloy are widely used in industry especially for marine applications since they possess an excellent balance among material such as general corrosion resistance, strength, weldability, weight compared to other Al alloys and formability. These properties are related to the magnesium content and to the applied heat treatments. They undergo the transition phases by precipitation which improves their mechanical properties. These improvements can be obtained by solution heat treatments and suitable ageing ones. Although they are already well studied, the questions concerning the stability of the microstructure and the effect of the various heat treatments are always asked. In this work, we present a study on the evolution of the precipitation reactions after quenching, exactly the evolution of the equilibrium phase (formation, coalescence, and dissolution), Al-12 wt. % Mg alloy aged at 250°C during different ageing times. The use of various experimental techniques as differential dilatometry, differential scanning calorimetry, scanning and transmission electron microscopy, X-ray diffraction and microhardness measurements, shows their importance and their complementarity in the study of ageing process in this alloy. The obtained results clarified the parameters that govern the stage of β particles appearance and the mechanical responses to the applied heat treatments.
La-Ni based alloys are being used in the commercial secondary nickel metal hydride batteries. Economical synthesis of these alloys may cause large scale utilization of them especially in the electrical vehicles. The electro-deoxidation, which is accepted as the revolutionary technique in the extractive metallurgy, is very promising in the hydrogen storage alloy synthesis since it provides direct synthesis of the alloys from their oxide raw materials. In this study A2B7 type La-Ni-Co alloys were synthesized from sintered mixture of La2O3 + NiO + CoO in the molten salt by the electro-deoxidation method at 850C and the electrochemical hydrogen storage characteristics of the synthesized alloys were observed. Sintering resulted in formation of the non-hygroscopic La2NiO4, LaNiO3, La3Ni2O6.5 and La4Ni3O9 phases depending on the Co content of the oxide mixture. The X-ray diffraction peaks indicated that La2NiO4 was the main La-Ni-O phase to initiate the LaNi5 phase formation. The target La2Ni7 phase formed much later than LaNi5 phase. It was observed the discharge capacities changed between 208 mA h g-1 (La2Ni7) and 332 mA h g-1 (La2(Ni0.8Co0.2)7) depending on the alloy Co content. This work clearly indicated that the electro-deoxidation was very effective and probably much more economical method in the synthesis of the hydrogen storage materials.
The effect of the combined addition of 0.039 % P + 0.015 % Ag as well as a nominal addition of 0.1 % of the de-embrittling elements of copper: B, Mg, Ca, Ti and Zr to give some variations in contents within the DHP specification limits on grain size structure at a constant casting temperature of 1130 °C were determined and compared to those at a constant casting temperature of 1150 °C under TP-1 casting conditions. These results showed that on decreasing the casting temperature from 1150 °C to 1130 °C, the degree of CET increased for a given DHP-Cu reference composition; the nominal Ag addition of 0.015 % to DHP-Cu was essential for grain size control; and that, in comparison to the corresponding DHP-Cu reference cast at 1150 °C or 1130 °C, no further grain refining action was observed due to B, Mg, Ca, Ti and Zr microalloying additions for the conditions studied.
The Magnesium alloys play significant role in the weight lowering of the means of transport. The principal difference between forming the magnesium alloys and steel is temperature used by magnesium. Although some forming operations of magnesium alloys can be done at room temperature, elevated temperatures are used in most applications. Because of the hexagonal close-packed crystal structure, the cold forming of magnesium alloys is restricted to mild deformation and generous bend radius. The magnesium plate is due to its lack of slipping systems hardly cold formable when the slip realizes itself only in basal planes. However, the slip takes place in pyramidal planes from 225°C as well. Formed magnesium alloys can be used as either BIW parts or the dashboard carrier in the automotive industry. AZ31 alloy is commonly used for such purposes. When considering the use of magnesium plates in BIW structure, a material characteristic verification were needed, which the stress-strain tensile test in temperature camera and strengthening curves. Such results serve to further design of pressing tool construction.
Refractory linings of metallurgical furnaces have two main purposes: to control the heat flow, and to contain high temperature liquids (metal and slag). Through a proper management of heat flows, a layer of slag called freeze lining crystallizes on the internal walls of the furnace thereby protecting the bricks from the very corrosive high temperature liquid slag. The thickness, stability and properties of this frozen slag are key parameters for the performance of a safe and stable process. In situ observations of the crystallization process during furnace operation are very difficult. To overcome this difficulty, the present work proposes a combination of heat flow monitoring, numerical modeling of heat transfer and the mineralogical characterization of the residual freeze lining after the furnace operation. The combination of these tools helps with the management of the process and the understanding of how to preserve the thermal balance of the furnace and the stability of the refractory lining.
Within a pilot furnace freeze lining, physical and chemical properties change depending on the operation parameters. The thickness of the free lining is one of the most important process variables to follow-up. An inverse heat transfer issue is solved using FLUENT in a simplified 1-D axisymmetric geometry of the furnace. After completion of the pilot, the freeze lining of the furnace is analyzed and characterized. All the significant evolutions in the operating parameters (temperature variation, slag chemistry change) are recorded within the oxide layers of the skull. Additionally to characterization, the crystallization paths that occurred during the process can be calculated using thermodynamic equilibrium computations.
This work provides a multi-disciplinary approach to understand usually unobservable phenomena within the furnace, allowing an estimation of the thickness, and physical and chemical properties of the freeze lining inside furnace.
This paper reports on the results of a study of the mechanical properties of sinters made of a new iron-based material, which is becoming increasingly popular in the manufacture of diamond impregnated tools as an economical substitute for cobalt and cobalt alloys. The sinters were formed by hot pressing a mixture of iron and bronze powders. Their properties were compared with those of hot pressed cobalt SMS powder. The specimens were analyzed for density, porosity, hardness, expansion and tensile strength. The fracture surface topography and the material microstructure were analyzed with an electron scanning microscope and a light microscope. The study involved determining the effects of the content of the powder on the chemical composition of the sinters as well as the influence of the fabrication process on the microstructure and mechanical properties of the material. The investigations show that the new iron-based material is inferior to cobalt; however, because of a favourable combination of hardness, yield strength and ductility it seems suitable for general purpose applications.
The Al-Zn-Mg-(Cu) alloys are used in various fields of industry (aerospace, aeronautics ...) because of their high mechanical properties attributed to the finely dispersed precipitates. However the phenomena of precipitation and the mechanisms which govern them are subject of intense research.
Our aim is to study the phase transformations and precipitation kinetics during heating in a calorimeter for underaged states. This study concerns the effect of copper addition on the precipitation phenomena in Al-Zn-Mg-(Cu) system alloys. We carried out a study of these phenomena by using the differential scanning calorimetric (DSC) and we completed this study by microhardness measurements. The analysis of the curves obtained by DSC suggests the presence of two intermediate phases and there are a number of types of equilibrium precipitate which differ from one alloy to another by the number and by the nature of these precipitates. On the other hand the microhardness measurements suggest that the addition of Cu increases the microhardness and the number of equilibrium phases in this system of alloys.
In this work, and in the temperature range of 300 to 875 K, The co-segregation of sulfur, carbon and phosphorus is treated at the surface of polycrystalline copper. We found that at high temperature, the sulfur surface concentration reaches 26%. Equilibrium and non equilibrium surface segregation energetic properties of sulfur were calculated after carrying out tests. Diffusion activation energy in the surface layer is E=136-15 kJ/mol. within the inspected temperature range, we have settled the diffusion equation for sulfur in the surface sublayer of copper.
The paper describes the metallurgical, technological and heat treatment aspects of rheocasting technology, especially method using mechanical swirling for reaching proper structure in semisolid state. Mentioned aspects are described by structures of AlSi7Mg alloy observed by light microscopy. Values of selected mechanical properties reached by different heat treatment modes are presented. Mechanical properties were measured by conventional and also by indentation.
The effect of ageing on microstructure and Vickers microhardness of fully lamellar Ti-45Al-5Nb-0.2B-0.75C (at.%) alloy was studied. The experimental procedure for preparation of the studied alloy included induction melting of pure elements, centrifugal casting of cylindrical bars and hot isostatic pressing of the bars to eliminate porosity. A fully lamellar γ(TiAl)/α2(Ti3Al) microstructure of the samples was achieved by the heat treatment consisting of solid solution annealing in a single α phase field followed by the cooling to room temperature. The ageing experiments were performed at three different temperatures of 750, 850 and 950 °C up 650 h in protective argon atmosphere. During the ageing the Vickers microhardness first increases with increasing ageing time and after reaching maximum values it decreases. The microstructure analysis by optical microscopy, scanning electron microscopy and X-ray diffraction analysis (XRD) show that the variations of measured microhardness values with the ageing time are connected with precipitation hardening. The peak microhardness values measured in the samples aged at 950 °C for 8 h are connected with the precipitation of carbides mainly of Ti2AlC type. The age softening observed after the ageing at 950 °C for 650 h results from the coarsening of the carbides and partial dissolution of the α2 lamellae.
Mechanical properties of tungsten, which is a candidate material for plasma facing components in fusion devices, prepared by spark plasma sintering were determined by compression and instrumented indentations tests. The indentation tests were carried out using Anton Paar nanoindentation device with two different indenters. Berkovich indenter was used for determination of indentation hardness and Young’s modulus. The results were treated by Oliver-Pharr method. Indentation techniques with spherical indenters are less frequently used than those with sharp indenters but they offer variation of strain with the indentation depth and should therefore be more explored as an alternative to the classical tensile tests. The technique based on multiple instrumented indentation cycles at the same penetration location was performed with a spherical indenter with radius 20 um. Each cycle consists of indentation, unload and reload sequence which serves to determine the flow curve using well known Tabor formula. These techniques of determining mechanical properties are highly advantageous because of their non-destructive character and low requirements on the volume of the investigated material. Local stress-strain behavior obtained by this method was compared with the results of compression tests. The microstructure of spark plasma sintered tungsten was characterized by metallographic analysis. The fracture surfaces developed by the sample cracking during indentation tests were examined in SEM.
Hydrogen storage in two Mg-In-C alloys with different In concentration cIn was studied in the temperature range from 250°C to 350°C after five-years-ageing at room temperature. The both alloys show acceptable cycling stability, however, the storage capacity of the alloys decreased from about 5 wt. % H2 to about 2,5 and 3.1 wt. % H2 by higher cIn and lower cIn , respectively after 5 years. The sorption kinetics degraded much more by high cIn than by cIn . PCT isotherms and DCS patterns were measured for the both materials. It was found that the hydrides responsible for hydrogen storage in alloy with higher cIn are slightly more stable.
Strain and temperature distribution field during FSW included plunging and welding stage was simulated using licensed software Deform 3DTM with the Lagrangian Incremental formulation settings. Non-uniform strain and temperature distribution field was observed. Developed model has a good agreement with experiment. Microstructure of friction stir weld was analyzed. Significant grain size refining was observed.
The ultrafine Cu–3 vol.% Al2O3 and Cu–3 vol.% MgO powders with comparable nanocrystalline structures were prepared by thermo-chemical technique and mechanical milling followed by hot extrusion. The study compares an influence of the two different oxide dispersoids on strengthening of the copper matrix after thermo-deformation consolidation of the powders into a bulk compacts and annealing of the compacts at elevated temperatures. The as-extruded Cu–Al2O3 alloy exhibits a homogeneous, thermal stable nanostructure up to 900 °C due to the dispersed alumina nano-particles that effectively strengthen crystallite/grain boundaries and inhibit grain growth. In the Cu–MgO material, the MgO particles are less efficient barriers against the grain growth due to their agglomeration into coarser particles (>50 nm) during the consolidation. A negative role here is a weak coherence of particle/matrix interface. The as-extruded Cu – MgO alloy is characterized by a bimodal grain size microstructure, a low hardness and it is structurally stable only up to 200°C due to the recrystallization processes. The results indicate that the choice of a suitable dispersoid for a given matrix is one of the deciding factors for thermal stabilization of the nano-grains.
Generally, the refurbishment of degraded turbine blades by reheat treatment processes, which the blades are made of cast nickel based superalloy, grade Inconel 738, usually consist of solution treatment with one or two steps of precipitation aging. Solutioning treatment with temperature range of 1125ºC- 1205ºC for 3 hours was selected to carry out in this study and then following with double aging processes, which include primary aging at 1055ºC for 1 hour and secondary aging at 845ºC for 24 hours. To simulate the effect of the possible change of temperature during solution treatment such as the temperature dropping down, which can be sometimes obtained by error or malfunction of heating furnace, the dropping temperature level during solution treatment was chosen to decrease till the level of 845ºC in various conditions, which usually happens in practices then immediately being heated up again to selected solution temperature level. The various selected temperature dropping time programs were performed during solution treatment. The maximum number of temperature droppings during the single solution treatment is up to 4 times. From the received results, it was found that the effect of temperature dropping during solution treatment has extremely influenced on the final refurbished microstructures.
The purpose of this article is to research temperature field during friction stir welding (FSW). Experimental FSW of 2 mm sheets was provided with different rotation speed of tool for temperature determination. Aluminium alloy AW 6082 T6 was chosen as a material for workpieces. Temperature was measured by thermocouples. Influence of the tool rotation speed on temperature distribution was estimated using experimental results. An analytical heat source model of FSW developed before was improved by taking into account not only friction at the contact surfaces or close to the contact surfaces under the tool shoulder and at the tool probe sides but also influence of the plastic deformation in the weld nugget on heating of the workpieces. Capability of the improved model in comparison with experimental data was proved. The temperature distribution was calculated by means of numerical simulation. Influence of backing plate on the temperature distribution was compensated by means of the Newton’s boundary conditions. The developed numerical FE-model of FSW was tested with experimental results. The results of numerical simulation are in good agreement with experimental results. Maximum temperature distribution across the weld centreline and along the weld centreline during FSW was estimated using developed FE-model. Maximum and minimum temperature under the tool shoulder was defined.
Jet cooling is used in many industrial applications. A typical application is the ingot casting process. Cooling water flows into the mold, where it is distributed through a system of channels into holes that are very close together. For better homogenization, the water flows from the leading edge and then hits the surface of the aluminum ingot.
To obtain realistic results from numerical simulations, it is necessary to know the boundary conditions for each cooling scenario. It is not possible to use analytic solutions or multiphysics simulation software to obtain realistic heat transfer coefficient (HTC) curves which represent the cooling intensity of the nozzle or jet. Boundary conditions can be obtained by experimentally reproducing the same conditions in the laboratory and measuring temperature dependence over time. Evaluating the data is done using the inverse task, which calculates the surface temperature and HTC. Temperatures are measured using shielded thermocouples which are installed very close to the sample surface. The final goal of this work is to determine the cooling intensity of the casting system for different situations: changing the amount of water and cooling regime - continuous or pulse. The HTC curves from the calculated surface temperature data is used as boundary conditions for a numerical model which can simulate temperature distribution inside the ingot during the cooling process.
In the last 20 years, the technical progress made it possible the use of very hard materials in several fields like manufacturing parts for the car industry, the railroad coaches, the nuclear power, the aeronautics and the mechanical industries.
In this paper, it was studied the evolution of the superficial layer subjected to a non-conventional treated steel, during the wear tests. The material was subjected to the thermo-chemical treatment (nitro-carburized treatment in plasma, or ion nitriding, or laser nitriding treatment) applied after thermo-magnetic treatment regimes.
The structural aspects of the superficial layers of the steel are studied after the wear process, using an Amsler type machine, taking two sliding degrees at different contact pressures and testing in time. The tests were done to detect the sustainability to the material, the evolution of the superficial layer characteristics through different tests and to establish the influence of these thermo-magnetic treatments regimes.
Mechano-chemical processing route appears to be a novel technique for synthesis of nano – sized materials of composite type. The work is focused in the synthesis of Nb3/Al2O3 intermetallics matrix composite by mechanical alloying (MA). For this purpose, a mixture of aluminium and niobium (V) oxide powders with different amounts of aluminium was subjected to high energy ball milling. The structural and phase analyses of powder particles before and after milling using different times changing the ratio of was conducted by scanning electron microscopy (SEM) and X – ray diffractometry (XRD). Thermal properties were detected using by differential scanning calorimetry (DSC).
Materials for long term implants must be highly corrosion resistant. Corrosion resistance of surface is closely connected to biocompatibility of concrete application. Surfaces of implants can also be treated for specific biological reaction of organism. The article is focused on corrosion properties of porous titanium with different level of porosity. This material was created by sintering titanium powder with different fraction of sodium chloride. This material is common for manufacturing of long term implants. Porous of the surface on implant from such a material ensure high level of osteointegration of the implant into bone. The surface of the implant can be also treated additionally. Electrochemical corrosion behaviour of this material was observed. Isotonic solution was used for these particular measurements. Open circuit potentials were found, corrosion rate and corrosion resistance was determinated by Tafel and Stern methods. Also characteristic corrosion potentials (potentials of depasivation and repasivation) were measured. Effect of porosity on corrosion properties was discussed. Surfaces of samples were observed by light and electron microscopy before and after testing. EDS analysis were made on surface of tested samples and inside of corrosion pits.
Study of structural and mechanical physical properties of metal powders is important considering the processes in powder metallurgy. The procedural behavior of copper, iron and aluminum powders depends on many parameters. Therefore metal powders are most thoroughly characterized with size, shape and distribution of particles. In this research work the attention is paid not only to properties of individual particles, but also their collective, volume mechanical and physical quantities such as flowability, aeration of powders or compression. For the samples of copper, iron and aluminum powder has been determined particle size distribution, particles shape and surface topography of the sample using the EDF Z profile (extended depth of field) in connection with their mechanical and physical properties.
The smooth, spherical aluminum particles show without one degree, the angle of internal friction so called "Ideal bulk material", unlike the iron powder with grains of rugged structure with internal friction angle of 43°. These way defined Fe particles with distinct ruggedness of surface show a low degree of compressibility or any other method of formation. In the field of aeration it is difficult fluidizable powder. This demonstrates not only the material classification into group B according to Geldart, but also the aeration test result itself. 3D microscopic evaluation of copper powder particles shape has been defined as micro leaf-shaped. The Cu sample corresponds with pronounced compressibility 4.6%.
4 volume % of nano sized Al2O3 dispersed α-Fe powder materials with nanocrystalline was produced by simple milling with a mixture of the pure Fe, Al, and magnetite(Fe3O4) powders as a starting powder. The milled powders were hot pressed (HPed) at the elevated temperature, followed by hot isostatic press (HIP) for the further densification. The microstructure of the consolidated materials was characterized by standard metallographic techniques such as TEM (Transmission Electron Microscopy), STEM-EDS (Energy Dispersive Spectroscopy), and XRD (X-ray Diffractormeter). Mechanical properties of the materials were determined by compressive yield test and micro Vickers hardness test at room temperature. The grain size estimation was attempted for the materials by XRD, using the scherrer’s formula and TEM pictures. The microstructure of the materials was comprised with a mixture of a homogeneous distribution of Fe and Al2O3 nano grains. The 0.2% off-set yield strength and micro Vickers hardness of the materials were as high as 824 ± 39 MPa and 3.70 ± 0.1 GPa, respectively.
Structured sheet metals are becoming more and more popular for using in lightweight constructions. In the present research three different schemes to produce structured sheet from aluminum AW6061-T6, namely stretch forming (two type of die) and stamping using elastomer, were investigated. Evaluation criteria for application of these schemes were proposed. Numerical models for each technological scheme with some assumptions were developed in the software package DEFORMTM. The dimensions of sheet were limited only by the thickness (1 mm) and for numerical simulation a little part of the sheet was used. Influence of FE-mesh (type and number of elements) on calculation accuracy was estimated. Also such characteristics as power parameters of process, fields of internal stress and geometry of resulting profile were estimated.
Deposits of 96/4 at% Ti/Ni were produced by low-pressure cold spray technique using heated air as working gas. The chemical composition of the 8 mm thick was kept in hypoeutectoid concentration. Samples of the deposited material were annealed at temperatures from 500°C to 1000°C for two hours in argon protective atmosphere. Selected samples were quenched directrly prom the homogenizing temperature of 1000 and subsequently evolution of precipitated and eutectoid was studied. Generally microstructural changes of material character during annealing were evaluated together with changes in the character of fracture behavior, local micro hardness of the evolving phases. Microstructure and chemistry of the newly formed phases was evaluated using analytical electron microscopy. DSC study was involved in order to characterize the precipitation behavior under eutectoid temperature.Gradual evolution of intermetallic phases by diffusion mechanism observed. The samples general shape was preserved during the heating process although formation of Kirkendall porosity was evident.
The possibilities of microstructure refinement of several gama-TiAl alloys by the massive transformation and the effect of refinement on compression properties are discussed in this paper. Two alloys were prepared by plasma arc melting using the water-cooled copper crystallizer and two other alloys were prepared by vacuum induction melting. All alloys were subjected to subsequent two-steps heat treatment, which consisted of the dissolving annealing followed by the ageing. This procedure resulted in the considerable reduction of the mean grain size from 200-340 µm to 70-35 µm. The microstructure refinement led to the increase of values of the plastic deformation in compression, namely from 9-17 % to 25-30 %. This effect denotes the substantial decrease of brittleness of these intermetallic alloys as a result of the used heat treatment.
Experiments were performed on the crystallization of a solution upon the action of the temperature gradient with the forming of mono crystals three wedges crystal system (prisms). We found that the fractal dimension of crystals equals 2.45, which is consistent with the literature data. Crystal growth is represented as the rd translation of each side of the crystal lattice with its own speed and with relation to the formation of similar structures fractals. A mathematical model of ultrasonic crystallization of a solution was proposed. The model is based on the combined use of differential transport equations of momentum, mass, energy and sound waves and a method of similarity and dimensional analysis. The calculated formulas for the concentration of the equivalent diameter of the formed crystals and the intensity of internal energy source, associated with the interaction of crystals with the hydro mechanical, heat and sound fields were obtained. Fractal interpretation of ultrasonic crystallization of the solution was made. It was found that on the growth of crystal size directly affects translation i.e. an increase in the number of sets of crystals of infinitely small size, correspond to the size of the crystal lattice. In turn translation of crystals depends on the geometry of the crystallizer and the physical parameters of external force fields, acting on the solution. A connection of results of the mathematical modeling with the results of fractal analysis of the ultrasonic crystallization of solutions was established.
Iron aluminides are perspective structural materials for high temperature use. Addition of Zr into Fe3Al matrix leads to formation of strengthening intermetallic phases, which affect their high-temperature behavior. The present work focuses on the behavior at high temperature, especially on the mechanical strength and coeffi-cient of thermal expansion with respect to the alloy structure. Transition temperatures are not affected by Zr-addition.
The aim of this work was to investigate and compare microstructure changes in squeeze cast heat treated Mg-2Y-1Nd-1Zn (WEZ211) and Mg-3Y-2Nd-1Zn-1Mn (WEZM3211) alloys. The WEZM3211 alloy was isochronally heat treated in 30 °C/30 min steps from room temperature up to 510 °C, the WEZ211 alloy was first isochronally heat treated in steps 20 °C/20 min up to 440 °C, quenched and isochronally heat treated again. Phase transformations were investigated by several methods: electrical resistivity and microhardness were measured after each heating step; transmission electron microscopy was performed in selected states; differential scanning calorimetry was realized in the temperature range 20 °C – 510 °C. Electrical resistivity curve of the WEZM3211 alloy exhibits a slight decrease around annealing temperature 150 °C and the main drop in the temperature range 240 °C – 330 °C. This drop can be ascribed mainly to two precipitation processes – formation of thin basal plates and subsequently prismatic plates. After annealing at higher temperatures oval particles containing Mn, Y were observed. Resistivity of the WEZ211 alloy shows two decreases connected with formation and development of thin basal plates. Microhardness of both alloys exhibits only insignificant changes during the whole treatment.
The Al-Mg alloy gives different combinations of good formability and weldability with sufficient strength achieved by the mechanism of solid solution hardening of Mg solute. As automotive applications of Al alloys have grown, the high-strength Al-Mg alloys have seen increasing use. Many researches have continued with the goal of increasing the strength of Al-Mg alloys. The benefits of higher Mg levels for increasing strength of Al-Mg alloys are counterbalanced by its tendency to promote oxidation if the product is not fabricated appropriately.
It is well known that the oxidation of Mg in Al melt can be prevented by addition of small amount of Be or Ca. But, beryllium is extremely harmful to human body and its application is strictly limited. The beneficial effect of Ca on oxidation of Mg has been well reported, together with embrittlement behavior in the condition of high temperature tensile load. Meanwhile, a specially fabricated Mg alloy containing Al2Ca phase has been patented to inhibiting Mg oxidation. So, it is worth to understand the effect of Al2Ca on high temperature compression behavior.
For this purpose, Al-5Mg containing different level of Al2Ca were cast into Y-block (20mm of thickness). The casting block was machined into cylindrical sample with 10mm of diameter and 12mm of height for high temperature compression test. The microstructure of the deformed sample were analyzed and discussed in order to understand the effect of Al2Ca addition on the compression behavior.
The wrought Al-Mg, 5000 series alloys have been widely applied to automotive, ship, building, beverage can, etc in the form of rolled sheet, because of their good formability, weldability, corrosion resistance and medium strength. Magnesium in aluminum forms solid solutions over a wide range of compositions and wrought alloys containing from 0.8% to slightly more than 5% magnesium are widely used.
The Mg solute has a strong tendency to oxidize during melting and casting, even after solidification also. The oxidation of Mg degrades process capabilities as well as quality and properties of products, which results in the limited application of Al-Mg alloys. Industrially, the trace addition of Be element has been added into Al-Mg melt to inhibit the Mg oxidation, even though it is extremely harmful to human body and not so effective due to its low content. Recently, a specially fabricated Mg alloy containing Al2Ca phase has been developed.
This study aims to assess the rolling fabrication characteristics of Al2Ca-contained 5052 and 5083 alloys, which were fabricated by using the Al2Ca-contained Mg mother alloy. The surface roughness of the slab, edge cracking and oil stain in rolling process will be addressed. Mechanical properties and strain hardening behavior of the rolled 5052 and 5083 sheets will be discussed in a variety of temper conditions. Finally, the forming result of an automotive component will be shown.
Commercial grade Al-Mg alloys are increasingly being introduced in structural and closure applications to light-weight solutions to improve their fuel economy and reduce gas emissions. The Al-Mg alloys combine a wide range of strength, good forming and welding characteristics, and high resistance to general corrosion. The strength of Al-Mg alloys is mainly controlled by solute strengthening and it increases magnesium content up to about 5.5wt.% without reducing ductility.
The solubility of Mg in Al is 14.9wt.% at eutectic temperature. So, the Al-Mg alloys with higher magnesium content over 5.5wt.% up to the maximum can theoretically show higher mechanical properties. The strong tendency of Mg solute in Al melt to oxidize prohibits from widening the application. Industrially, the oxidation of Mg solute can be suppressed by adding trace amount of Beryllium, even though it is extremely harmful to human body. And recently, a specially fabricated Mg alloy containing Al2Ca phase has been patented to inhibiting Mg oxidation.
The purpose of this study is to investigate tensile properties and microstructure of Al-7.5Mg alloy in a variety of as-rolled tempers. The Mg content over commercial range was selected to improve the mechanical properties. the alloy was continuously cast into a billet with 7inch of diameter. The billet was extruded into a sheet form followed by a cold-rolling. The tensile properties and microstructure of the alloy in a variety of temper were investigated and discussed.
In this study, hollowed sandwich structures made of AZ61 magnesium alloy were extruded for the railway application. They have 200mm long and 70mm high. Two hollowed sandwich structures were butted welded using friction stir welding method. The rotation speed of tool pin was fixed to 400rpm and welding speed was varied in range of 100, 200 and 300mm/min. The UTS and elongation of the welding region was best in the 400rpm-100mm/min case while 400rpm-300mm/min case was worst among three conditions. The 400rpm-100mm/min case showed 10% and 30% higher than 400rpm-300mm/min case in the UTS and elongation, respectively. The hardness of the welding region showed similar values in three cases.
Characteristic of standard sacrificial alloys on the base of aluminum is extremely low contents in them are the cathode impurity elements. Due to this requirement the stable electrochemical parameters and high efficiency of aluminum anodes is not always achieved. The raised content of impurities results in the chemical and structural non-uniformity of alloys causing of electrochemical heterogeneity in system metal-electrolyte that destabilizes and reduces operational properties of cast protectors. In all cases the anodes became expansive and their application in some cases not economical.
This paper presented data as to how to stabilize the electrochemical properties of sacrificial zinc anodic materials that contain aluminum, manganese, silicon and cadmium alloying elements with higher concentration of cathode impurities (iron, copper and lead) and possibility of use in the preparation of alloys from metals of technical grades. Discussed the principles of alloying that help to reduce and neutralize impurity elements.
Paper presents results of research on composites made from epoxy resin reinforced with glass fiber, modified with aluminum, zirconium dioxide and cobalt aluminate particles. The laminates are made of L-RTM technology using the laboratory test stand which is on the Department of Metal Working and Physical Metallurgy of Non-Ferrous Metals, Faculty of Non-Ferrous Metals, AGH University of Science and Technology. Prepared samples were used to mechanical properties, fatigue, flammability and impact tests. The test results allowed for determine the effect of additives in the form of metallic particles on the static and dynamic properties of epoxy laminates.
The connection between metal and ceramic occurs by physical, chemical and in small extent by mechanical forces, special attention is applied to the every stage of metal surface preparation before ceramics application. One of the method during manufacturing a permanent metal-ceramics connection used in dental technology is the surface blasting of the metal casts. The time and the kind of used blasting grit size (the surface roughness) have a direct impact on physical and mechanical forces present within the above-mentioned connection determining the strength of the connections and indirect impact on chemical forces – affects on the surface oxidation efficiency and give the ability to the uniform distribution of opaquer (interlayer) over the entire metal surface. The paper presents the results of microscopic cross-sections observation of Ni-Cr-Mo coated with opaquer and dental ceramics layers. On the basis of variables sandblasting parameters found that this treatment tends to increase the diversity of the surface. Short term (because a 15-second) sandblasting makes the metal surface irregular, and the presence of hollows and hills on the surface contribute to increased adhesion between layers of opaquer and ceramic. The usage of longer sandblasting time makes that the irregularities are rather rifts and burrs. In addition, the dimensions of the resulting irregularities restrains the correct and accurate surface oxidation of the alloy, but also restrains the correct and even surface coverage within opaquer Highly diverse of the alloy surface contributes to the numerous gaps, cavities and voids on the border of the metal - ceramic connection.
The Mg–11.5wt.%Zn–3.0wt.%Al and Mg–5.1wt.%Zn–3.3wt.%Al–0.1wt.%Ca alloys were squeeze-cast under a protective gas atmosphere (Ar + 1% SF6). Precipitation reactions were studied by differential scanning calorimetry at heating rates of 0.5 – 30 K/min. Electrical resistometry at 78 K and microhardness (HV0.5) at room temperature were performed additionally. The specimens were subjected to isochronal annealing with steps of 20 K/20 min up to 300 °C. The thermal measurements revealed two exothermic effects during linear heat treatment in the temperature range of 100 – 250 °C. In agreement to the thermal response, two stages of electrical resistivity decrease were observed in the same temperature range. The first process is also associated with hardening in both alloys (at ~ 180 °C). The lower thermal and resistivity changes were observed in the alloy with Ca-addition. Activation energies obtained from the thermal measurements using the Kissinger method for the two mentioned processes were calculated as Q1 = 124 kJ • mol-1 and Q2 = 133 kJ • mol-1 in both alloys.
The effect of low-temperature treatment on the structure and hysteretic properties of Nd-Fe-B magnets, which were prepared using strip-casting alloy (wt%) Nd -24%, Pr – 6.5%, Dy – 0.5%, B – 1 %, Al – 0.2%, Fe – balance and 2 wt % DyH2 addition, has been studied. Hysteretic properties of the magnets subjected to the optimum heat treatment are Br = 1.29 T, jHc = 1309 kA/m, Hk = 1220 kA/m, (BH)max = 322 kJ/m3. The subsequent combined heat treatment at 250 to 500oC (for 20 h) does not change the hysteretic properties. The degradation of magnetic properties (decrease in jHc and Hk to 1105 and 960 kA/m, respectively) is observed only after the repeated annealing at 550oC. The hysteretic properties of the magnets can be restored completely by heat treatment 1050oC (1 h) + 500oC (2 h). The data obtained demonstrate the higher thermal stability of hysteretic properties of magnets prepared from hydride-containing powder mixtures. The observed effect is attributed to the formation of a non-uniform Dy distribution in (Nd, Pr, Dy)2Fe14B principal magnetic phase grains.
Titanium and AISI 304 stainless steel were joined using an 0.1 mm thick aluminum foil interlayer at temperatures of 550, 650 and 700 °C for 1 h under 2 MPa pressure in vacuum. The interface microstructures of the bonded samples were observed in an optical and scanning electron microscope. The chemical analysis was performed with energy dispersion spectroscopy. There was investigated the effect of bonding temperature on joints microstructure, composition and hardness. FeAl3 and Fe2Al5 intermetallic layers have been observed at the stainless steel-aluminum interfaces. At the aluminum-titanium interfaces TiAl, TiAl2 and TiAl3 intermetallic layers were identified. The width of intermetallic layers for both interfaces increased gradually with the increase in bonding temperature. The irregular shaped particles of Al7Cr were additionally observed in aluminum matrix for joints that were transient-liquid-phase bonded at 700 °C. Hardness of joints achieved values from 220 to 870 HV and was higher than for base metals. The values of hardness for analogous intermetallic layers increased with the increase in bonding temperature.
The paper presents the problem of the analysis of data collected in the expert system of technological line of heat treatment of titanium alloys, focused on the development of control signals
and to define guidelines on process improvement.
Heat treatment processes of titanium alloys belong to the group of special processes, ie. the results are known only after their completion. Possible discrepancies may arise in operating conditions what in the case of aircraft type of production is not acceptable.
The process is carried out under the supervision of the key parameters, without the possibility of
assessing intermediate stages of the workpiece.
Comprehensive and reliable identification and appropriate to the needs analysis of the data is possible only in the case of a fully automated system. Equipping it with features inference emphasizes (highlights, enhance) its expert character.
Example presented in the paper concerns the exploration of the relationship between parameters of heat treatment of titanium alloys grade WT22 and properties of the product described by the strength properties, hardness and toughness.
It is important to refere these results to the weight and volume of the workpiece, including the location of the properties in the volume due to the different heating and cooling history of each area.
Because of the large number of parameters, experiments were designed to obtain a response to the desired change in their values.
The optimization of heat treatment conditions of Nd-Fe-B-based permanent magnets, prepared using the strip casting method, was carried out with the aim to enhance their coercivity Hcj and maximal energy product (BH)max, and improve the shape of the demagnetization curve. The initial alloy with the chemical composition (for high-coercivity magnets) of Fe - 67,05; Nd - > 19,50; B - 1; Dy - 6,00; Pr – 6,00; Cu – 0,15; Al – 0,30 (wt. %) in form of strips was submitted to hydrogen decrepitation and vibration milling. The obtained powder with the granulometry of 3-5 um was mixed with 2.5 wt. % NdH2 due to the improvement of liquid-phase sintering process and increasing in the coercivity as a result of the formation of continuous grain boundary. Structural characteristics and phase composition were investigated using scanning electron microscopy equipped with EDX microprobe, light optical microscopy equipped with digital camera and XRPD. The microhardness of the principal Nd(R)2Fe14B phase was measured. The magnetic properties were evaluated using automatic hysteresisgraph and vibrating-sample magnetometer. The maximal values of the coercive force Hcj of 1688 kA/m were achieved by the heat treatment at 500 °C. The increasing of this temperature to 550 °C led to a sharp drop in magnetic properties and microhardness. The specially designed Zeiss microscope was used to visualize the magnetic domain patterns on the surface of magnetic materials using the magneto-optical Kerr microscopy. The observed star-like domain structure indicates a good magnetic texture for permanent magnets. These data are of great importance for deciding the optimum heat treatment of Nd-Fe-B-based magnets.
Attempt to determine the heat flow kinetics in insulating moulding sand with aluminosilicate microspheres matrix in order to identify and modify its properties. Destination of moulding sand is pouring thin-walled skeletal casting 3D, characterized by strongly developed surface of heat dissipation and 1,5÷3 mm predicted connector thickness. Shows the results of computer simulation of temperature field in the mould. For the implementation of the research uses about eutectic aluminium alloy with silicon (AlSi12). Shows the results of the heat flow in the cast-mould system using experimental casting typically for thermal derivative gradient analysis (TDGA). The method was developed in the Department of Foundry of Silesian University of Technology. For the purpose of the own research the methodology has been modified by location most of the thermocouple not in the cast, but in the moulding sand. Thermocouple were placed in established and variable distances in the range of 0 to 8 mm from the surface of the casting. One of the thermocouple was placed in the geometric centre of the casting. Simulation study were performer, which aim was precision analysis of heat flow in the mould. This analysis is the basis for the designation of thermophysical and technological parameters of mould or core sand. The aim is to estimate the thermophysical of technology quantity in actual industrial environments. Application of the concept of TDGA methods in the assumption should allow to quickly obtain the information about thermal properties of mould without uses of complex thermal laboratory research. Assumed that the analysis of the temperature field gives a qualitatively comparable results to the standard determining of thermal properties in a function of temperature. Despite the simplifications, the importance of technological methods may prove to be attractive in the production conditions of a typical foundry.
Autogenous laser welding of thin magnesium alloy sheets was done. Material AZ61A of thickness 1 mm was laser welded by disc laser without using filler wire. Laser welding w/o filler wire is very demanding on sheet metal edges preparation, so different methods of edge preparation, e.g. shearing, milling, was done. Mg alloys have susceptibility to porosity, evaporation of alloying elements, spattering hot cracking and other. The research focused on finding optimum laser welding parameters for butt and ovelapped welds. Welds were evaluated optical metallography, visual and penetration test, SEM, microhardness and tensile strength etc. The sheet metal edges for butt welds must be prepared by milling, otherwise porosity was found. Edge quality is not important for lap joint welds, which is an advantage. Laser welding proved to result in very good weld quality, without any defect, yet the processing window was narrow.
Cobalt-based alloys (e.g. Stellite 6) are often used on surfaces which are required for the high resistance to abrasion (sealing surfaces of the fittings, etc.). These surface layers are commonly applied to low alloyed steel Grade 22 or martensitic steel Grade 91 by welding techniques using. When using armatures with these layers in energetic plants (high pressure valves) have shown operating experience that occurs in damage to functional layers often. The typical damage is characterized by cracking and flaking (release) of the functional layer.
This paper deals with the analysis of the causes of such damage to the surface layer of the ball valves (or their contact faces) after the low-cycle service application in superheated steam (550°C / 10MPa). Layers were applied to the steel AISI 316. For this research were used methods of metallography, chemical and SEM analysis, phase and XRDA microanalysis, hardness and microhardness testing. It was found selective cracking in the areas of a specific phase composition. The subsequently release of materials particles and other damage to the surface by these particles.
Metallic foams are materials with the broad applicability in many different areas of human activity (e.g. automotive industry, building industry, medicine, design, etc.). These metallic materials contain artificially created pores in their structure. These pores give them specific properties such as large rigidity at low density, high thermal conductivity, capability to absorb energy, etc.
The paper deals with an optimization of procedure for production of cast metallic foams with use of casting technology (infiltration method), which ensures rapid and economically feasible method for production of shaped components. In the experimental part conditions of casting of metallic foams with irregular inner structure and open pores made of ferrous and non-ferrous alloys by use of various types of filler material (precursors) were studied.
Various materials can be used nowadays for construction of vehicles, ranging from aluminum alloys and composite materials to high strength steels. For successful utilization of Al alloys, it is advantageous to use necessary calculations using FEM and computer simulation tests to verify engineering construction design. This can help to map and take advantage of the potential of the material. On the other hand, the proper observance of the manufacturing process, the chemical composition and microstructure of selected structural material can provide us with important information. Material purity, homogeneous chemical composition, the correct production process, technological processing etc., are decisive for the further use of the material for the construction elements of the technical device in the form of a fully-functioning components with the required lifetime.
Research in the field of magnetic materials based on Nd-Fe-B is focused on the improvement of certain magnetic characteristics by alloying of suitable elements (Co, Dy, Tb, Ga), extending the thermal stability of these permanent magnets, improving their corrosion resistance and the creation of nano-structure modifications. Magnets based on Nd-Fe-B are susceptible to corrosion, especially in humid atmospheres. The corrosion resistance of these magnets is a function of the structure, temperature, degree of environment humidity and Nd-rich phase reactivity. The paper is focused on determining and comparing the corrosion resistance of selected material (Nd,Pr)2Fe14B (produced by powder metallurgy) in selected environments. For comparative purposes, unalloyed carbon steel (C ≤ 0,10% wt., CSN 11321) was tested under the same test conditions. On the basis of electrochemical polarization measurements there were determined polarization curve, corrosion characteristics and parameters (corrosion potential, polarization resistance, pitting potentials, etc.) of mentioned selected materials in aqueous solutions (Na2SO4, NaH2PO4, NaCl). Salt spray test was performed on other samples of these materials. The heterogeneous structure of magnetic material and uneven and/or localized corrosion was observed using microscopy. In the sodium chloride solution a higher corrosion resistance reached steel in comparison with the magnet, in an environment of sodium sulfate results were not clear (depending on the pH, surface condition). The magnetic material exhibited a much higher resistance in the solution of NaH2PO4 in comparison with the corrosion resistance in other test solutions.
Amorphous alloys are characterized by high values of hardness and tensile strength, great corrosion stability and also favorable soft magnetic properties. Industrially, they are produced as ribbons with thicknesses below 60 µm; many technical applications require the joint of the ribbons from such alloys by welding or soldering processes. Due to their low thermal stability, the welding process becomes a critical issue because of the need to avoid the crystallization of the welded joint. One of the welding methods where the temperature of the components remains under the solidification scale point is the welding with stored energy in capacitors. The characteristic of this method is that energy absorbed by the AC network is not used directly in the welding process but is converted by the power circuit in a current pulse. The paper sets of the process parameters and values that ensure the formation of welded joints between Ni-based amorphous ribbons with thicknesses of 35 µm and respectively 50 µm, without the solidification phenomena being involved.
In this paper, a friction stir welding(FSW) was applied for the extrusion plate of magnesium alloy AZ61 to confirm the difference in material properties of the weld region due to the change of welding conditions such as the rotational speed and the welding speed. The rotation speed was 400, 600 and 800rpm and welding speed was 200, 300 and 400mm/min respectively. Dimension of the magnesium sheet was 500X100X5mm(length, width, thickness) and butt welding was employed. Tensile test was carried out after the welding process. As a result, 800rpm-200mm/min case shows the maximum value in tensile strength. However, 800rpm-400mm/min case demonstrate the maximum value in yield strength. Therefore, when the rotational speed was 800rpm, the strength of the overall weld was confirmed to be larger than the other conditions. The hardness of stir zone(SZ) in weld region was higher than other zones.
Material properties in cast condition are largely influenced by its structure. Here you can influence, for example the speed of solidification, or metallurgical operation. In the case of aluminum alloys, casting into moulds with a low cooling effect of vaccination is commonly used material. Submitted work deals with the influence of the cooling effect of common foundry moulds achieved microstructure of casting alloys on the base of Al-Si. Used moulding materials were mixed with inorganic and organic binders. Other types of materials have been significantly different cooling effects – metal and plaster form.
The NiTi alloy was remelted by electron beam zone melting. The initial state of the NiTi samples was after swaging. After electron beam zone melting was prepared samples for optical metallographic analysis, scanning electron microscopy analysis and EDX analysis. Next analysis was made to determine the concentration of interstitial elements (C, O, N). The obtained results were compared to NiTi alloys prepared previously with other technologies (centrifugal casting and so on).
The paper deals with the characterisation of the structure and phase composition of selected types of nickel alloys. Castings were prepared by vacuum induction melting and centrifugal casting. Samples of Ni-Al-Mo based alloys with various contents of molybdenum were directionally solidified by Bridgman method in corundum tubes with specified apex angle. Rate of solidification was 50 and 20 mm/h. The samples were used for structural analysis in longitudinal and transverse direction. The structure is significantly influenced by the process of directional solidification. Microstructural characterisation of materials was performed with use of scanning electron microscope. Distribution of individual elements in phases was captured on linear analysis. These alloys do not exhibit significant chemical heterogeneity. The samples are composed of a phases Ni3Al and (Ni) with various contents of molybdenum. The existence of a separate phase (Mo) was not confirmed. Determined values of microhardness show the dependence on molybdenum content and rate of directional solidification.
A TIG torch was used as the heat source for surface alloying of Mg. The alloying material in the form of an AlMg4.5Mn wire was directly fed into the melt pool. It was found that the microstructure and thickness of the alloyed layer was dependent on the processing parameters. When higher currents were used, the 2 mm thick Al-enriched layer produced on the Mg substrate consisted of dendrites of a solid solution of Al in Mg and a eutectic (Mg17Al12 + a solid solution of Al in Mg) distributed in the interdendritic spaces. Surface alloying of Mg at lower currents led to the formation a thinner alloyed layer (about 1 mm) comprising mainly an Mg17Al12 phase. The alloyed layers containing Mg-Al intermetallic phases exhibited higher hardness than the Mg substrate.
In the last decade, multicomponent alloys arisen as new promising family of materials. The effect of milling parameters, namely milling balls size, milling speed and time on synthesis of inequiatomic AlCoCrFeNiTi0,5 mechanically alloyed (MA) powders in planetary ball mill were studied. Alloying behaviour, morphology, size and homogeneity of powders were observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). During MA, a supersaturated Cr based solid solution with BCC structure was formed after 24 hours of milling, with significantly reduced grain size. It was revealed, that selection of milling conditions have a great influence on milled powders properties. In general softer milling condition result in decreased particle size and homogeneity
For production bearing welds at resistance spot welding there is very important value about number of welds made by electrodes at which is created regular welding spot higher than certain minimal value and thus also efficient bearing capacity. During welding there is with increasing number of welded spots simultaneously also wearing of electrode working area, changing of conditions for creation weld joints and thus also their quality. In consequence of electrical, mechanical, thermal and metallurgical loading there are changes in electrode working area geometry, changes in roughness and fouling of working areas, changes of mechanical and physical properties of electrode material. There is very important influence of the electrode working area surface temperature on the operating life. Within the scope of this paper there is description of new female electrode caps cooling system by liquid carbon dioxide. There is evaluated influence of cooling on the female electrode caps temperature course in the zone of its working area. On the basis of metallographic evaluation there is examining influence of electrode cap cooling mode on the change of its working area geometry and thermal affection. Upon the base of results from mechanical tests there is evaluated decrease of dimension and bearing capacity with increasing number of welded spots.
Hot-extrusion of the chips and other highly fragmented materials is a very convenient way for aluminium alloys scarp processing. It is possible to achieve ready or semi-finished products in one step of material forming - directly from the chips to the bulk material. The mechanical properties of such processed material are affected by various extrusion conditions: temperature, extrusion speed and cross-section reduction ratio λ. The variation of cross-section reduction ratio has an effect on chips bonding quality, which in turn results in different mechanical properties. The objective of the present study is to analyze mechanical and structural features of 6060 and AlSi11 aluminum alloys after plastic consolidation by hot extrusion with different cross-section reduction ratio in the range of 7 to 45. Aluminum alloy in the form of chips, were preliminarily cold compacted to produce cylindrical billets. The as-compressed billets were then hot extruded at 450°C. The samples cut from as extruded rods were subjected to tensile test and structural SEM observations. Based on obtained results minimum extrusion ratio required for sound bonding of chips was established.
Ti alloys as biocompatible are widely used in prosthetics and in implantology. The Puasson coefficient μ is equal to ratio of relative transversal compression to relative longitudinal lengthening. Debye model sets the conditions existence stand waves in solid state. The quantum nature of elementary oscillators takes into consideration. Тherefore waves, that elementary oscillators excite, can’t carry the energy. There are stand waves. One oscillator produce 3 waves: 1 longitudinal and 2 transversal. Debye temperature was determined after the formula with Bol'cman constant, Plank constant, Avogadro number, middle gram-molecular mass, density, longitudinal US velocity, transversal US velocity. Temperature dependence of internal friction Q-1(T) and elastic module E(T) (directional of inelastic-elastic body) and 2D, 3D AFM microstructure of VT3 Ti alloy after mechanical and thermal treatment is represented.
Thus, the measuring of IF background Q-10 after different heat, mechanical, radiation treatments gives information about the changing of the thermoelastic strains fields σi in Ti alloys. The growth of heights IF maximums QM-1 testifies the growth of structural defects concentration, and the broadening of IF maximums ΔQM-1 here represents the relaxation process of structural defects new types in Ti alloys. The correlation between elastic module Е, pressure P and temperature Т may be presented az surface (“directional surface of elasticity body”) before and after satiation.
Deformation twinning is frequently observed in materials with hexagonal crystal lattice. It plays important role in plastic deformation of such materials. Twin regions have often lamellar shape and twin boundaries are usually oriented along invariant planes. However, non-invariant twin interfaces are also observed. Several examples of such faceting will be presented. Mechanisms of faceting will be discussed on the basis of atomistic simulations.
Properties of materials made from elemental metallic powders deposited by cold gas dynamic spraying were studied – Fe-Al, Fe-Cu and Fe-Ni. The samples were annealed in protective atmosphere and macroscopic features like porosity were evaluated before sectioning. All samples were subjected to microstructure and thermal properties study. The mixtures were deposited on an aluminium substrate, so that the resulting material was free-form consolidated from the powder mixtures by high impact energy without melting or oxidation of the individual powder particles. Solid state diffusion and melt involving reactions in the deposits were assessed by DSC analysis. The samples have been subjected to microstructure and phases analysis by scanning electron microscopy (SEM) and X – ray diffraction (XRD) analysis. The results from microstructure study and DSC observations are evaluated with the aim of possible feasibility to use the ColdSpray/annealing route as manufacturing technique for materials with useful properties.
The alloys based on the Ni3Al intermetallic compound are a base material for the high-temperature industrial applications. The molybdenum addition improves their strength at room and high temperatures. The high melting point of molybdenum restricts the use of conventional casting methods, such as induction melting, during the preparation of alloys from pure components. Therefore, the process of plasma metallurgy was used for preparation of a Ni-15Mo (wt. %) master alloy, which was subsequently used for preparation of a Ni-7Al-14Mo (wt. %) alloy by the process of induction melting. Castings of the Ni-7Al-14Mo alloy were directionally solidified in a resistance furnace working on principle of the Bridgman method at growth rates of solidus-liquidus interface of 20 and 50 mm/h.
The Ni-15Mo master alloy, the casting and the directionally solidified rods of the Ni-7Al-14Mo alloy were subjected to chemical and structure analysis. The matrix of Ni-15Mo master alloy was homogenous and without precipitates and it was formed by the MoNi8 phase. In the case of Ni-7Al-14Mo alloy, the matrix of the casting and the directionally solidified rods was formed by the Ni3Al phase and a solid solution of aluminum in nickel mutually arranged in a mesh. Small phases rich in molybdenum were situated along the grain boundaries. The structure of the casting and the directionally solidified rods of Ni-14Mo-7Al alloy was polycrystalline. Controlled conditions of directional solidification led to a formation of coarse-grained structure oriented mostly in the direction of growth of solidus-liquidus interface.
The metal foams are materials with great potential for use in various fields of industry. The pores created deliberately in the structure give them many exceptional properties; one of the most important features is the ability of energy absorption. In the experimental part the castings of metal foam with a regular internal structure were manufactured by simple foundry way (infiltration of metal into the cavity of the mold is filled preform). The samples made from porous material were subsequently tested in mechanical testing. For a comparison of experimental data 3D math ideal model (model with perfectly smooth wall) was created. The initial model was calculated by using an explicit dynamics, which is primarily used in areas of extreme deformation with a small increment of time, e.g. car crash tests. The based on these results it is concluded the opinion, whether it is a convenient time to continue in the optimization of metal walls on the way of simulations or it will be necessary to continue with creating of physical models and experiments.
Commercial grade 6000-series aluminum alloys are characterized by good corrosion resistance, electrical conductivity and specific strength. These advantages combined with good formability make the 6000-series alloys very attractive for various industrial applications.
Present work describes comparison of hot extruded 6061 aluminum alloy, initially prepared by different processing routes. In particular, industrial material (cast and homogenized), rapidly solidified powders and flakes and machined scraps (chips) were utilized. Mechanical properties combined with structural observations were performed for as extruded materials. Additionally, the effect of cold rolling deformation on the structure and mechanical properties was studied as well. It was found that all processed materials show similar response to mechanical stimulus.
Highly dispersed 6061 material can be effectively consolidated via hot extrusion, which opens new possibilities for solid state recycling. However, it was shown that contrary to expectations, rapid solidification as a method of materials processing has a negligible effect on the 6061 aluminum alloy properties.
Platinum have become a metal, which is today necessary for every new car production due to its catalytic role, mainly reduction of toxic gases. Prices and demand for platinum are shown as well as the possibilities to recover this metal from secondary materials, especially spent auto catalyst. Paper presents the short review of platinum production from primary materials – the kind of ores, places where platinum is mined. However, resources of primary platinum are limited and quickly depleted. Platinum is also received from by-product obtained from the treatment process of other metals such as copper or nickel and these methods are also shortly shown. Finally, to meet the future demands and protect the platinum resources the hydrometallurgical, pyrometallurgical and even biometallurgical processes of platinum recovery from different waste e.g. electronic scrap, spent catalyst are counted and briefly characterized. The main focus was given on the spent auto catalyst – the general way of platinum recovery was given in more detail.
Two heat-resistant monocrystalline Ni-based alloys were studied before and after series of high-temperature tensile tests. The plastic properties of the alloys were investigated using EBSD method. Schmid factor was chosen as a parameter suitable for analysis of crystal lattice orientation evolution.
Some differences of plastic behavior of the materials were discovered. Plastic insability in one of the alloys was found.
Mechanical alloying (MA) of light metals and other metal-oxide additives is a very promising method for production of high strength metallic composites. Of particular interest are the aluminum matrix composites reinforced by heavy metal oxides (MeO), which cannot be produced by means of common metallurgical processes due to the high reactivity of the components.
In this work, mechanical alloying and hot extrusion method was used to prepare Al based composite reinforced by 12,8 wt-% addition of AgO. Structure observations of as-extruded Al-AgO composite revealed a very well consolidated nanoscale structure without any visible cracks or pores. Annealing experiments were performed to test the thermal stability and the effect of chemical reaction between components on the material structure. The results revealed that annealing of the material at 773K results in reduction of the materials hardness from 178HV to 120HV for as-extruded material and sample annealed for 7 days, respectively. Received results will be discussed in relation to the features of the structure as studied by SEM and TEM.
Iron aluminides are one of the most attractive intermetallics for commercial applications due to their excellent corrosion resistance in combination with high specific strength. Proper design of thermomechanical parameters and precise control of the microstructural evolution are essential for successful processing of these alloys. This research evaluates the deformation behavior of P/M iron aluminide and discusses the importance of the processing parameters. Iron aluminide alloy powder was consolidated to full density by hot pressing. Cylindrical compression specimens were machined from the compacts and subjected to hot compression tests in order to characterize the material behavior under various thermomechanical conditions. Moreover, numerical simulations of the investigated alloy forging were performed. The boundary conditions for the simulations were prepared on the base of the experimental tests. Chosen results of the simulations were compared with the results of forging the investigated alloy performed in industrial conditions. The study showed good agreement of the experimental and numerical modeling results, what confirmed a proper design of the boundary conditions used in this study.
In the present work we investigated the corrosion resistance of candidate lead-free solder alloys in simulated seawater conditions. Four different alloys were studied: Sn-0.7Cu, Sn-3.5Ag, Sn-0.3Ag-0.7Cu and Sn-0.7Cu-3.5Ag (composition in wt. %). The alloys were prepared by induction melting from high purity Sn, Ag and Cu lumps. After melting, the materials were solidified by pouring the molten alloy on a piece of cold steel plate. Chemical compositions and microstructures of the alloys were investigated by field emission gun scanning electron microscope (JEOL JSM–7600F) coupled with an Oxford Instruments energy dispersive X–ray spectrometer. Each alloy was heterogeneous as it was found to consist of β-Sn and different binary intermetallic compounds (IMC). The alloys were corrosion-monitored in 3.5 wt. % NaCl aqueous solution at 21±2 °C. This solution represents the simulated seawater conditions. The electrochemical polarization was carried out in a standard 3–electrode cell provided by Sensortechnik Meinsberg Ltd. The potential–current density curves were measured by using a PGU 10V–1A–IMP–S potentiostat/galvanostat (Jaissle Electronic Ltd., Germany). The corresponding corrosion potentials and corrosion rates were determined by Tafel extrapolation of the experimental polarization curves. The effects of chemical composition and sample microstructure have been evaluated. Conclusions for the solder alloy corrosion resistance in humid environments are provided. The local nobility of individual IMCs is discussed. The results can be used as a guideline for selecting the proper lead-free solder composition for microelectronic applications.
ACKNOWLEDGEMENTS:
This work was supported by the Grant Agency VEGA project no. 1/0068/14.
The iron aluminides seem to be very perspective materials for use in high-temperature structural applications. They are promising materials for a possible replacement of high alloyed steels of P91 or P92 type. But it is very important to know the coefficient of thermal expansion (CTE) of iron aluminides for use as structural materials at high temperatures. It can also be determined phase transformations in the alloy from CTE measurement.
In this paper there were studied the differences in CTE-curves between Fe3Al (D03 structure) and FeAl (B2 structure) type iron aluminides. It was investigated the coefficients of thermal expansion and phase structure of three samples in temperature range 440 – 1200 °C.
In the present investigation, transient liquid-phase bonding was performed between pure titanium (Grade 2) and stainless steel (X5CrNi 18-10) using 0.1 mm thick nickel foil as an intermediate material. The process was carried out at the temperatures of: 850, 875, 900, 925, 950, 975 and 1000 ⁰C for 60 minutes under the compressive stress of 2 MPa in a vacuum. The effects of temperature on the microstructure diffusion brazed joints were characterized in the optical and scanning electron microscopes. The inter diffusion of chemical species across the diffusion interface were evaluated by electron probe microanalysis. The structural examinations have shown that temperature is critical factor to control the microstructure. The diffusion zone on the borders of the joined materials becomes wider with the increase in temperature. The structure of the joints from the titanium site was composed of the eutectoid mixture αTi+Ti2Ni and layers of intermetallic phases Ti2Ni, TiNi and TiNi3. The stainless steel nickel interface is free from any reaction layer up to 875 °C, above this temperature thin layer of reaction appears. The microhardness test across the joints indicates that the hardness in the interfaces reaches higher value than for titanium and stainless steel, and it achieves value from 320 to 528 HV.
The process of aluminum powders mechanical alloying was researched and powders with reference size and shape were obtained. The influence of the mechanical alloying process parameters on the powder compositions structure and properties is shown. The analysis of the possibility of compacting for mechanically alloyed aluminum-based compositions was carried out by methods of mathematical and physical modeling. The temperature range in which sealing is possible and subsequent treatment of plastic blanks, which structure corresponds to the structure of the material powder particles obtained by mechanical alloying, was defined. The processes of equal channel angular pressing, whch was performed to compact the material, and subsequent rolling, which allows to carry out the deformation of layered material and to keep the integrity of the less plastic composite core were simulated and practically realized. Practical recommendations for the implementation of the process to obtain the blanks from composite material based on mechanically alloyed powders of aluminum – rare-earth metals system with special radiation-protective properties.
Complex study of alloys based on FeAl aluminide was leading in the fifties of the last century to the proposal of. The composition of the binary Fe-Al alloy was modified by C and Si. This alloy with excellent corrosion and heat resistant properties was used to replace the high chromium and nickel alloyed cast iron.
The investigations performed recently on Fe-40 at.%Al type alloys with carbon contents 1.9-3.8 at.% and aluminium up to 43 at.% were designed to explain in more detail the origin of the structure and mechanical properties of the mentioned material.
It is the purpose of this contribution describes the effect of Al and C on the structure of iron aluminides with the composition of Pyroferal©. The appearing and morphology of carbide Al4C3 and of graphite is described in the as cast and annealed state.
Present paper is focused on solid state recycling (SSR) method through hot extrusion of different forms of aluminium alloys scrap such as chips, cans or foils. Common feature of the scraps is highly developed free surface that leads to the substantial material losses during conventional re-melting process. Therefore, SSR was found to be very promising technique for recycling of highly fragmented materials. An important parameter of SSR extruded materials is profiles surface quality. In this work, extrusion factors such as temperature and extrusion speed are discussed with respect to surface quality of obtained profiles. Additionally, charge material morphology and structure are analyzed in relation to the types of surface defects. It was found, that for all processed materials such as 3xxx, 4xxx and 6xxx aluminium alloys, good product quality can be obtained by application of proper extrusion temperature, which was determined to be 400C or above. Structure analysis revealed that main difficulties during SSR are lack of sound bonding between chips (wrought aluminium 3xxx and 6xxx series) and surface cracking due to breaking of hard particles (4xxx alloy series).
Plastic consolidation offers a good alternative for traditional scrap recycling, especially for the highly fragmented forms of materials obtained from machining process. In this method aluminum chips are being pre-compacted into a form of solid billets and then hot extruded at elevated temperature. Present work describes influence of the temperature and extrusion speed on the mechanical properties of flat 6060 aluminum alloy bars. In order to test different materials morphology, profiles were extruded from two distinctive types of scraps: large chips produced by means of turning process and fine ones produced by CNC machining. Before plastic consolidation chips were pre-compacted to the form of billets with a diameter of 40 mm. Cold compacted billets were then extruded at temperatures of 400oC and 450oC with a press ram speed of 0.5 mm/s and 3 mm/s. Extrusion ratio of 25 was kept constant during all experiments.
Results revealed that mechanical properties of fine chips extrudates exhibit similar properties to those obtained by casting and extrusion procedure. On the other hand, samples prepared from large chips are characterized by lower mechanical properties. Density measurements combined with microstructure observations revealed a very well consolidated material without any porosity, which suggests good quality of chips bonding.
The paper outlines the history of development of magnets, from magnetite ore, through to the production of steel, Alnico, ferrite, samarium and neodymium magnets. The directions of further research on the improvement of the magnetic properties of magnets in the future are also discussed.
The coatings based on (Ti-Zr-Nb)N were fabricated by vacuum-arc deposition of the Ti+Zr+Nb cathodes in the nitrogen atmosphere. Their physical and mechanical properties as well as tribological characteristics have been studied. The coatings are characterized by a columnar structure, their hardness reaches 44.57 GPa. The adhesion strength of coatings reaches 66.77 GPa, the friction coefficient of the «cover – Al2O3» is 1.1. It has been determined, that the hardness of the investigated coatings significantly depends on the pressure of the reaction gas. The coatings are promising as protective coatings for friction pairs and cutting tools. The purpose of the work is studying of ion-plasma coatings formation particularities by multiple system sputtering based on Ti+Zr+Nb, and carrying out the analysis of obtained coatings’ physical and mechanical properties. The coatings were formed by vacuum arc deposition. Unit cast target (cathodes) was used on the basis of 30 atm. % Ti, 35 at. % Zr and 35 atm. % Nb as the vaporized materials. Molecular nitrogen was used as the working gas. The thickness of the coatings in the experiments was 4.0 microns. The surface morphology fractograph fracture, track friction were investigated in a scanning electron microscope JSM-6390 LV. The use of multi coatings based on carbides is very promising is, borides to ensure the high performance properties of the complex, nitrides and silicides of transition metals. Nanostructured coating of (Ti-Zr-Nb) N was obtained by vacuum arc evaporation cathode-cast in a nitrogen gas reaction medium. Multicomponent films have a pronounced columnar structure. Elemental composition was obtained by the vacuum arc deposition of coatings (Ti-Zr-Nb) N, depending on the physical parameters of the deposition process, in particular the pressure of the reaction gas nitrogen.
High entropy alloys are a new material class with promising structural and mechanical properties in wide range of applications. In principle they consist of five or more elements in equimolar concentrations resulting basically in single phase microstructure. TaNbHfZrTi alloy was developed by Senkov for high temperature applications.
Since all of these elements are biocompatible the TaNbHfZrTi alloy can be investigated as a prospective bio implant material. The alloy was prepared by vacuum arc melting, no annealing treatment was applied. Tensile test and hardness test at room temperature were performed with very good results; Yield strength 1150MPa, Rupture strength 1200MPa, Vickers hardness 350 HV30 . Microstructure and fracture morphology was also investigated.