Aluminium and magnesium are young metals comparing to lead or iron; but today commonly used. Their production from year to year is constantly increasing. This is because their universal application, eg. in aircraft industry, automotive industry, pharmaceutics, electric and engineering industry, packaging. To the main producers of this metals belong: China, Russia and Canada/Israel. The amount of aluminium and magnesium production in the last 24 years was presented considering also the changes in main producers. There is also presented the changes of magnesium production from electrolytic method to silicothermic reduction (e.g. Pidgeon method). Basic information concerning obtaining aluminium from ores by the Bayern method and electrolysis of alumina as well as receiving from scrap via recycling was given. The essential dangers for the environment are also mentioned. What is more, there is also presented the perspectives of further aluminium and magnesium production.
Solidification process plays an important role in the production of metallic materials. Conditions of this process, which allows for the transformation of metals from the melt to the solid state, considerably determine mechanical properties of semi-finished products. It is therefore worth to pay attention and control this process. Nowadays, metallurgists frequently utilize computational solidification models that enable the numerical investigation of solidification processes. Most of these computer tools are based on interface capturing methods, which are straightforward and quite easy for implementation to the form of a computer program. However, a main drawback of these methods is their accuracy in the determination of the moving interface front, which separates the solid and liquid phases. It implies that the energy conservation is not precisely fulfilled in the vicinity of the interface and this also negatively influences the accuracy of the predicted temperature distribution. The paper presents the front tracking method, which enables to overcome the mentioned issues and allows for investigation of the microstructure and of the growth of dendrites. Pure aluminium, which solidifies at a constant temperature, is considered in the presented study. The front tracking method, the enthalpy method, the effective heat capacity method and the temperature recovery method are used for simulations. Simulation results gained with the use of different computational approaches are evaluated and compared to experimental results and to an exact solution of a 1D Stefan problem. Conclusions of the study indicate that the front tracking method is a more accurate tool for investigation of solidification processes than other tested methods.
Atomized powder of an Al7075 alloy was high energy ball milled at room and cryogenic temperatures with different milling parameters and compacted by spark plasma sintering (SPS) method. The influence of processing parameters on phase composition was studied by X- ray diffraction. The microstructure was investigated using light and scanning electron microscopy. The mechanical properties were characterized by microhardness measurements.
The atomized powder contained a large volume fraction of intermetallic phases located predominantly in continuous layers separating cells or dendrites in the interior of individual powder particles. Consolidation by SPS destroyed partially this morphology and replaced it by individual particles located at boundaries of original powder particles, at cell boundaries or arranged in chains in previous dendritic regions.
High energy milling and cryo-milling destroyed most intermetallic particles and enriched the matrix by solute atoms. The high deformation energy introduced into the powder during milling enhanced microhardness up to 220HV. Consolidation of milled powders by SPS led to the formation of very fine-grained structure with the grain size even below 1 μm and with the fraction of high-angle boundaries about 0.9. Two main types of heterogeneously distributed precipitates were found. The irregularly shaped precipitates with a size about 1 μm seemed to encompass areas with rod like nano-precipitates in most samples. Simultaneously, a drop in microhardness to 118HV was observed after SPS, predominantly due to a release of introduced deformation energy.
In this paper a new High-Entropy Alloy from Al-Ti-Co-Ni-Fe system was examined. The alloy was synthesized by arc melting process. On the basis of theoretical assumptions, the alloy should obtain BCC structure. To verify theoretical assumptions, the structure was characterized by X-ray diffraction. Because High-Entropy Alloys with BCC structure exhibit very high hardness with accompanying fragile, the hardness measurements were conducted. Additionally, microstructural observations using scanning electron microscopy, equipped with energy dispersive spectroscopy X-ray spectrometer for elements distribution, were carried out. It was stated, that the obtained equimolar High-Entropy Alloy from Al-Ti-Co-Ni-Fe system has high hardness but is very brittle. During hardness measurements from the tips of the indentation cracks spread. A significant segregation of the elements was also observed.
Strips from Al-Mg-Sc-Zr alloy were prepared by twin-roll casting using the vertical operational plane. Microstructure evolution during annealing was observed by light optical microscopy and electron microscopy. A redistribution of solutes was monitored by resistivity measurements.
High entropy alloy AlCoCrFeNiTi0,5 was produced by a combination of mechanical alloying (MA) and spark plasma sintering (SPS) processes. In our study we have investigated the effect of four different sintering temperatures (ranging from 1150 to 1300 ºC) on microstructures, phase composition and microhardness of sintered samples by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and Vickers microhardness test. In all cases, full density has been achieved. The influence of sintering temperature has been determined to be very small for cases when powder is in solid state during sintering. For highest sintering temperature of 1300 ºC, partial powder melting took place, significantly decreasing obtained hardness.
Severe plastic deformation methods preserve dimensions of the material and reduce the grain size down to submicrometers. Twin-roll cast strips prepared from aluminium EN-AW-3003-based alloy with a small addition of zirconium and chromium were subjected to deformation by Constrained Groove Pressing (CGP). The microhardness distribution along the strip cross-section reflects an inhomogeneous distribution of total equivalent strain simulated by finite element method only for one CGP cycle. Subsequently, after the second and third CGP cycle, microhardness saturates and its distribution becomes more homogenous. Evolution of microstructure and mechanical properties during subsequent annealing was studied by transmission electron microscopy and electron backscatter diffraction. Inhomogeneous recovery of dislocation structure and recrystallization were observed during this annealing.
The aim of this investigation was to study the effect of welding heat input and postweld natural aging on residual stress, microstructure, and precipitation distribution in different zones of dissimilar friction stir welding of 8 mm thick plates of 2024-T3. It was found that atomic diffusion occurs at the interface of the materials in the stir zone of the joints. Transmission electron microscopic investigations showed that reprecipitation of fine Guinier–Preston zone, β′, and η′ precipitates resulted in increased micro-hardness in the SZ after natural aging. An increase in welding heat input resulted in decreased maximum tensile residual stress and increased size of the tensile residual stress region.
Existing exact knowledge on fatigue crack growth parameters and characteristics is an essential condition for an application of Damage Tolerance design philosophy in dynamically loaded structures. Measurement of fatigue crack growth (FCG) in an Al 7175-T7351 alloy of a particularly high homogeneity was carried out as a part of the Proficiency Test Programme organised by General Electric Aviation, USA, in a collaboration with the company Exova in France. To pass the test programme successfully, a particular attention was paid to improve and verify DCPD (direct current potential drop) method being used for the crack length measurement. The attention paid to the experimental methodology bored fruit - the results obtained were close to the average of results measured at different accredited worldwide aircraft laboratories. Additionally, an investigation of effects of overloads on fatigue crack growth and retardation was carried out. Results of FCG rates were very self consistent, likely due to the material homogeneity. Retardation effects of overloads of the magnitudes 2.7-times and 3.0-times of the maximum load in the constant range fatigue loading were significant. The overloads resulted in substantial crack closure effects, which, however, did not occur immediately, but just after further fatigue crack extension, comparable with plastic zone size. The works was completed by fractographical analysis of fracture surface with the aim to find knowledge on detailed mechanisms of FCG after the overloading.
This experiment deals with preparation of Al plus 25 weight % Cu powder mixture. The powders were mixed, compressed using a double-step cold isostatic pressing (CIP) procedure and subsequently sintered in vacuum either at 500°C or at 550°C for 60 min. Analyses of chemical compositions of the pre-sintered samples performed using scanning electron microscopy showed a distinctive difference in structural phases compositions in the two samples featuring a presence of aluminum oxides (Al2O3) and brittle intermetallic phases (CuAl2) in the two samples, respectively. The presence of both was also confirmed by microhardness measurements. The effects of the individual structural phases on formability of the two pre-sintered samples were evaluated with severe plastic deformation via high pressure torsion (HPT). While the sample featuring alumina exhibited sufficient formability at room temperature, the other sample featuring intermetallics was formable only at an elevated temperature.
This study reports the effect of LaB6 particles on the Al-5 wt.% Si matrix powders and composites in regard of physical, microstructural and mechanical properties. Two different types of LaB6 particles such as laboratory-synthesized (LaB6(S)) and commercial (LaB6(C)) were used as reinforcement materials. (LaB6(S)) were prepared by mechanochemical synthesis (for 5 h) and HCl leaching of La2O3-B2O3-Mg powder blends. In order to obtain hybrid powders, Al-5 wt.% Si, Al-5 wt.% Si-2 wt.% LaB6(S) and Al-5 wt.% Si-2 wt.% LaB6(C) blends were mechanically alloyed (MA'd) for various durations (1, 2, 3, 4, 6 and 8 h ) in a Spex™ Mixer/Mill using hardened steel vial/balls with a 10/1 ball-to-powder weight ratio. A hydraulic press with a uniaxial pressure of 450 MPa was used for the compaction of the as-blended/MA’d powders. Green compacts were sintered at 570 C for 2 h under Ar gas atmosphere. X-ray diffractometry (XRD), optical microscopy (OM) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) techniques were utilized for the microstructural characterization of the as-blended/MA'd powders and sintered composites. Particle size measurement and differential scanning calorimetry (DSC) analyses were also conducted on the powder products. Sintered samples were characterized by density and Vickers microhardness measurements and sliding wear tests. With increasing MA time, mechanical improvement in composite properties was observed. Al-5 wt.% Si-2 wt.% LaB6(C) MA’d for 8 h had the highest density value (98.11%) and the lowest relative wear loss (0.441). Al-5 wt.% Si-2 wt.% LaB6(S) MA’d for 4 h had the highest microhardness value (115.25±10.12 MPa).
In this study, Al-7 wt.% Si powders and composites hybridized with niobium boride powders were prepared by a combined method of mechanical alloying and pressureless sintering. Niobium boride powders containing NbB-NbB2-Nb3B4 phases were mechanochemically synthesized (for 5 h) from Nb2O5-B2O3-Mg blends and purified with HCl leaching treatment in our laboratories.Laboratory-synthesized NbB-NbB2-Nb3B4powders were incorporated into the Al-7 wt.% Si matrix powders with the amount of 2 wt.%via mechanical alloying for different durations (1,4 and 8h) in a Spex™ Mixer/Mill using hardened steel vial/balls with a ball-to-powder weight ratio of 7/1. Mechanically alloyed Al-7 wt.% Si-2 wt.% NbB-NbB2-Nb3B4powders were compacted usinga uniaxial hydraulic press with a pressure of 450 MPa and green bodies were sintered at 570°C for 2h under Ar gas flowing conditions. Characterization investigations of the hybrid powders and composites were performed using X-ray diffractometer (XRD), optical microscope (OM), scanning electron microscope/energy dispersive spectroscope(SEM/EDS), particle size analyzer (PSA) and differential scanning calorimeter (DSC). Sintered samples were also characterized in terms of density, Vickers microhardness and wear volume loss. Amongst all the samples, an average density value of
95 %, the lowest wear volume loss of 0.289 mm3 and the highest microhardness value of 94.01±9.17 N/mm2 were obtained by the utilized powder metallurgy techniques.
Magnesium is an essential structural element of the human body and together with its alloys is characterized by mechanical properties close to the properties of bones. Similar materials are thus intended for the manufacture of biodegradable implants. In present work we have studied the properties of magnesium alloys with gallium concentration in the range from 1 to 5 wt. %. All alloys were prepared by conventional casting and subsequently extruded at 300 °C. Structure, mechanical properties in tension and compression and corrosion behaviour of studied materials were characterized. Alloys in all cases contained eutectic phase Mg5Ga2 which was dissolved during the thermal treatment T4. Alloying of magnesium by gallium led to a significant increase in mechanical properties of the alloys. Corrosion rate in the as-cast conditions was deteriorated with increasing Ga content. A partial improvement of corrosion resistance occurred after the subsequent heat treatment and extrusion.
Magnesium alloys are a part of a group of lightweight alloys, which are important in practical use in constructions. The paper shows the results obtained by research into welded AZ91 magnesium alloy. Within the scope of research microstructure examination and tensile testing were done. Magnesium alloy was welded by two methods – 141 (TIG) and 522 (laser gas welding). The values of tensile strength of welded joints in majority cases were higher than values of tensile strength of the base material. The microstructure examination and chemical analysis made it possible to explain the phenomena occurring in the AZ91 during welding.
The influence of Inconel 718 nanoparticles on the mechanical and physical properties of magnesium has been investigated. Samples of magnesium with 3, 6 and 10 wt% of Inconel 718 nanoparticles were prepared using disintegrated melt deposition technique followed hot extrusion.
The microstructures of the composites were examined by a light microscope and SEM. Information on the grain size and texture was analyzed using an FEI Quanta 200 FX scanning electron microscope equipped with EDAX EBSD camera and OIM software was utilized for EBSD observations. A significant effect of the nanoparticle content on the grain size was revealed.
Nanocomposites were deformed in tension and in compression over a wide temperature range from room temperature to 300 °C at a constant crosshead speed giving an initial strain rate of 5.5 x 10-3 s-1. The true stress-true strain curves were determined. The flow stress is significantly influenced by the test temperature; it rapidly decreases with increasing temperature. A substantial asymmetry in the tensile and compressive mechanical properties was observed. The possible mechanisms responsible for the deformation behaviour are discussed.
The linear thermal expansion coefficient of the materials was measured over a wide temperature range from room temperature to 400 °C. The possible mechanisms are analyzed and discussed.
Metals and their alloys are used in medicine especially for hard tissue replacements where special properties are required (e.g. biocompatibility, low modulus or corrosion resistance). Another important group is biodegradable materials for fixation devices and stents where the corrosion rate and biocompatibility are essential properties. Stainless steel or Co-Cr-Mo alloys are still used despite their lower biocompatibility and high modulus (~210 GPa). Titanium and its alloys (Ti6Al4V) have good biocompatibility, corrosion resistance and lower modulus (~110 GPa). On the other hand newly developed beta-titanium alloys are promising materials due to their combination of excellent biocompatibility, high strength (> 1000 MPa), very low Young’s modulus (~50 GPa) and corrosion resistance. These alloys were developed primarily for bio-applications and they seem to have the best known combination of properties for this purpose. Another important group of metallic biomaterials are biodegradable materials. They are used for short-term applications and eliminate the problems and risks of reoperations. This paper is a short insight of currently used and developed metallic biomaterials.
The beta-titanium alloys are used for bioapplications (e.g. orthopaedic or dental implants) due to their excellent properties like biocompatibility, corrosion resistance, high strength, low Young’s modulus). The processing of these alloys is essential for their properties and therefore processing parameters should be chosen properly. In this work the effect of solution treatment temperature on properties of Ti-35Nb-Zr alloys has been studied by means of light microscopy, X-ray diffraction analysis and DSC analysis. The Ti-35Nb-2Zr alloy was prepared through powder metallurgy process (blended elemental powders, cold isostatic pressing and sintering). Sintered specimens were hot forged and solution treated at temperatures 800, 850, 900, 950 and 1000°C for 0.5hrs and water quenched. The grain size changes from 35 to 75μm. In addition precipitation processes have been observed along with precipitate coarsening. The α-phase precipitation has significant influence on the matrix grain growth.
The work presents investigation of microstructural evolution of pre and post heat treated (HT) Selective Laser Melting (SLM) manufactured Ti-6Al-4V. The as received SLM samples composed of fine acicular α’ martensite within prior β grains were solution treated (ST) above the β-transus temperature, followed by a complementary HT within the α+β range. The microstructure and the mechanical properties of the ST and HT samples are compared to SLM samples HT within the α+β range. The difference between the two HT is discussed. After low HT temperatures, the microstructure was composed mainly of martensitic α' phase, whereas, after high temperatures HT, bi-phasic microstructure with needle-like elongated α-phase grains and a mixture of lamellar α+β in between, was observed as the dominant microstructural component
Titanium alloys and their weld joints find wide application, in particular in aircraft, automotive and chemical industries, because of their outstanding specific strength and corrosion resistance. The high reactivity of these alloys and the strong degradation effect of elements contained in the atmosphere (H, N and O) make it necessary for these alloys to be welded in protective atmospheres or in vacuum. From this viewpoint, Electron Beam Welding is an advantageous welding technology, in large series production in particular In the paper, the effect is studied of the spot diameter and beam focusing on the penetration depth and the weld shape in the Ti6Al4V alloy. The results obtained are complemented with an analysis of the microstructure and mechanical properties (microhardness, tensile tests) measurements across the welds.
Modern metallurgy - has a close collaboration with many other industrial fields and also with gas production industry. Using of hydrogen and nitrogen atmospheres in steel production and rolling show us metallurgy industry in role of a big consumer of industrial gases. But from other side metallurgy plants and companies always plays role of suppliers for gas industry. This type of collaboration is not new, but in last decade’s development of powder metallurgy provides new possibility for two industries connection on the way of creation new types of energy storage systems, based on metal hydrides and start to find a road for a new energetics.
Using of intermetallic compounds for hydrogen storage in solid form with the formation of chemical compounds (metal hydrides) with the possibility of sorption and desorption, provides energy storage systems with hydrogen densities greater than in the liquid and gaseous states.
Hydrogen storage in intermetallic systems in the near future can be most energy efficient and less energy consuming way of hydrogen storing. The increasing of pressure storage and the realization of hydrogen storage temperatures, sharply differing from ambient temperatures significantly increases the energy consumption for hydrogen storage.
In that article we want to describe real applications and conditions of intermetallic systems, and possibilities to use metal compounds for creation energy storage systems and using that systems in real life.
A2B type Ti-Ni hydrogen storage alloy, which has also dissolved Zr in it, was synthesized directly from TiO2-ZrO2-NiO mixture in the molten CaCl2 electrolyte by the electro-deoxidation method at 900C. Sintering of the oxide mixture at 1100C for 2 h did not cause formation of any mixed type Ti-Zr-Ni oxide. Short time electro-deoxidation (< 5 h) yielded Ti3O5, CaTiO3, CaZrO3, Ni and Ti2O3 formations upon reduction of the sintered oxide mixture. Extension of the electro-deoxidation time up to 10 h caused disappearance of all these reduction products and there remained only TiO and Ti2Ni phases. Presence of TiO lasted about 15 h and then the target alloy structure with 100% Ti2Ni phase was obtained with the maximum amount of dissolved Zr in it. The synthesized alloy was prepared as electrode and it was observed that it had maximum discharge capacity of 200 mA h g-1. The capacity retention rate of the electrode, however, was relatively low probably due to the barrier action of the formed oxide layer on the alloy surface. As the charge/discharge cycle increases the thickness of the oxide layer also increases and then the in/out diffusion of the elemental hydrogen becomes difficult.
This study is focused on the effect of boron addition on solidification behavior, segregation and mechanical properties of directionally solidified nickel-base superalloy. boron addition decreases the liquidus and solidus temperature, and increase the freezing range of alloy. Furthermore, the solidification rate of alloy changes with the different content of boron, which will also alter the segregation of the solute elements. The rupture life of the alloy is also changes with the different content of boron.
In this paper, the effects of various production parameters on the microstructure, mechanical and tribological properties of TiB2-reinforced NiAl/Ni3Al intermetallic compound were investigated. The experimental results showed the possibility of producing sintered composites of NiAl/Ni3Al with 4 vol.% TiB2 by Spark Plasma Sintering. It was shown that satisfactory results had already been obtained during sintering at 1150 °C and a pressure of 16 MPa. The composites had a nearly theoretical density after sintering already at 1150 °C for 10 min. under pressure of 48 MPa. Applying these parameters also caused achieving the largest Young's modulus (ultrasonic test) and hardness (HV1). Optical microscopy, scanning electron microscopy and X-ray diffraction analysis were used to characterize produced samples. The distribution of alloying elements within intermetallic compound was determined by EDS. TiB2 reinforcing particles were evenly distributed in the matrix. Tribological tests were made by ball on disc process. The friction coefficient and wear rate of the composites were measured.
It is well documented that the addition of antimony in pure lead increases tensile strength and reduced elongation. The goal of the present work is to identify the cause of these phenomena by investigation of the effects of the addition of Sb (1.25%) on the structure of pure continuously cast lead and lead alloy rods. The microstructure and morphology of both pure lead and lead 1.25% antimony were examined by digital optical microscope and scanning electron microscope respectively. Energy Dispersive X-ray Spectroscopy (EDX) was used to identify alloying elements. The results showed that the effect of additions of antimony on mechanical properties of lead-antimony alloys is mainly due to the solid solubility of the antimony element. Homogenized distribution of the antimony results in a decrease in the grain size of the pure lead. These smaller grains mean higher strength so long as there is a homogeneous grain structure
Application of Sn-Pb solders in electronic and electro-technical applications gradually decreases due to the toxicity of Pb and being replaced by lead-free Sn-Ag, Sn-Cu and Sn-Ag-Cu solders with melting temperature under 500 K. Among them Sn-Ag alloy is one of the most promising candidate for applications due to favourable combination of higher electrical conductivity and mechanical properties (higher elastic modulus, yield strength and tensile strength).
In this article we present preparation and microstructure characterization of lead free Sn-Ag solder. The alloys with different content of silver (3.5, 6.75 and 10 wt.%) were prepared by rapid solidification technique - melt spinning. Microstructure
of the alloys, phase composition, chemical homogeneity and temperature of melting were studied by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. The prepared alloys exhibit fine, homogeneous microstructure consisting of Sn and Ag4Sn phases. Higher Ag content increases melting temperature of the alloys.
Since the discovery, metallic glasses (MS) and bulk metallic glasses (BMG - metallic glasses with a minimum diameter of 1 mm) have opened up a novel engineering field in the world of metallic materials. These types of glassy metals with good glass forming ability have excellent mechanical, magnetic and corrosion resistance properties, that are dissimilar to properties of conventionally used crystalline materials. Particularly, Cu - based BMG have attracted much attention due to their excellent mechanical properties, exhibiting compressive strength of over 2200 MPa and great ductility values (up to 18 % for Cu47,5Zr47,5Al5 at.% at room temperature) connected with large critical casting thicknesses (up to 12 mm for Cu42Zr42Ag8Al8 at.%). Conical ingot of the composition of Cu60Zr30Ti10 at.% of diameter 1 - 5 mm was prepared by suction casting method at the Institute of Materials Research in Košice. In order to investigate the critical casting thickness of the alloy, ingot was transmitted by monochromatic synchrotron radiation of the wavelength of 0.020671 nm (59,9799 keV) while X-ray diffraction patterns were recorded by 2D detector. Passing from the amorphous to crystalline section, critical casting thickness (CCT) was determined as largest diameter, where the structure remains still amorphous. In order to demonstrate the difference between amorphous and crystalline state of the same alloy, ingots of critical (ø ~ CCT), subcritical (ø < CCT) and supercritical (ø > CCT) diamaters were cast. Compression test was performed and strength of the materials was compared.
Fe-Ni-Al alloys remain convenient object for studying the spinodal decomposition and formation of modulated microstructure. Microcrystalline Fe2NiAl alloy with the nominal composition Fe51.1Ni23.5Al23.7Si1.7 was prepared by melting in an induction furnace using pure metals. Detailed studies of the microstructure, phase composition and magnetic properties by TEM, X-ray diffraction, Mossbauer spectroscopy and magnetic measurements of as-cast Fe2NiAl alloy are reported. The alloy was subjected to homogenization at 1240oC and subsequent cooling at a critical rate to an intermediate temperature Tq = 900 - 20°С followed by water quenching. Cooled samples have been characterized by modulated structure formed during the solid-solution decomposition into β- and β2-phases within the miscibility gap. The coercive force was found to exhibit a nonmonotonic dependence on the temperature Tq, which shows the minimum Hc ≤ 40 Oe at Tq = 850oC. The high quality modulated microstructure giving the maximum Hc = 650 Oe was obtained after cooling to 650 -20oC at the critical rate. The Mössbauer spectrum measured after cooling to Tq = 850oC is similar to that measured after quenching in water at 1240oC. The obtained results allow to interpret the nonmonotonic behavior of Hc on the temperature Tq as a function of composition changes of the β- and β2-phases and fineness of modulated microstructure.
Investigated the Effect of low temperatures on the magnetic properties of single-crystal permanent magnet of an alloy of Fe–Co–Ni–Cu–Al–Ti. It is revealed that at temperatures below 50K there is an increase in saturation magnetization up to 10% and the theoretical value of the residual magnetic induction of up to 1.4 T. Also investigated the change of the phase composition of the material.
Powder metallurgy is widely used in technical practice to manufacture products with specific properties. In the field of ammunition powder metallurgy technology is used to produce frangible bullets designed for small arms.
This paper presents results of pressing experimental cylindrical parts from mixture of metal powders Fe – Sn. The parts with diameter of 9 mm were compacted by cold pressing in a cylindrical rigid die without sintering. By changing the axial pressed force in the range of 10 to 40 kN various physical and mechanical properties of the produced samples were achieved. The achieved results could be used in development of pistol frangible bullets of caliber 9 mm.
TiB2 is one of the choices for high temperature applications, due to its refractoriness and high strength at elevated temperature.Especially, TiB2 ceramic is characterized by an excellent combination of properties comprising high melting point (~3250°C), hardness (25.5 GPa), wear resistance, electrical and thermal conductivity, good creep resistance, and excellent chemical stability.However, consolidation difficulties, poor fracture toughness, and poor oxidation resistance generally restrict the extensive applications of monolithic TiB2. Research efforts have shown that addition of SiC enhances the oxidation resistance by forming a protective SiO2-rich layer and improve fracture toughness of borides.Furthermore, studies in recent years have indicated that graphene nanoplatelets (GPL) addition can significantly improve the mechanical properties of ceramic matrices. In the present study, graphene nanoplatelets were integrated into (20-x)SiC-80TiB2 (vol.%) composite powder with x = 0, 0.5, 1, 3, 5, 7 and 10 vol.% contents. The resulting powder mixtures were sintered by spark plasma sintering (SPS) at 1800°C under a uniaxial pressure of 40 MPa with a 5 min holding time. The sintered composites were then characterized with respect to their densification, microstructure, oxidation behavior and mechanical properties.Development in oxidation resistance as a result of formation of protective layers and fracture mode change with the combination of SiC and graphene nanoplatelets will be described in this presentation.
Besidw all its good properties -high hardness,chemical inertness,high electrical and thermal insulation-low fracture toughness limits applications of alumina.A way to overcome the low fracture toughness is to fabricate it as composites. In this study alumina-YSZ(yttria stabilized zirconia) nanocomposites reinforced with GNPs (graphene nano platelets) were fabricated by using SPS (spark plasma sintering ) technique at 1400 °C for 300 s under a pressure of 40M Pa. GNPs-YSZ-Al2O3 powders were obtained by ball milling of graphene palatelets,alumina and YSZ powders using ytrria stabilized ZrO2 balls. The effects of varied GNP contents (1,3,5,7 %vol,2%wt.) On the microstructural features, mechanical properties and cell viabilty of nanocomposites were investigated.
A comprehensive meshless numerical model was developed for the simulation of direct chill casting under the influence of low frequency electromagnetic field. The model uses mass, momentum and energy conservation equations to simulate the solidification of aluminium alloy billets. Electromagnetic field equations are coupled with the fluid flow and used to calculate the Lorentz force. Mixture formulation of transport equations is used to handle the two-phase flow. All time-dependent partial-differential equations are solved with the diffuse approximate method. An explicit time stepping scheme was used. Three different types of boundary conditions for the heat transfer were incorporated, therefore the effects of hot-top, mould chill and direct chill are all used in the simulation. The use of meshless methods and automatic grid generation made it possible to investigate complex inflow conditions, including sharp and curved edges. A time dependant adaptive mesh was used to decrease the calculation time. The macroscopic transport model results are used in two other independent models to solve the solid mechanics and microscopic grain growth equations. An industrial casting case of an aluminium alloy billet with the radius of 144 mm was simulated. The effect of low frequency electromagnetic force on temperature, liquid fraction and fluid flow was investigated.
The aim of this paper was to verify changes in mechanical properties and structural characteristic of the 91W6Ni3Co powders mixture after cold swaging, before which the initial powders were pressed using cold isostatic pressing (CIP) and pre-sintered. Swaging was carried out at room temperature in one pass from the initial diameter of 30 mm to the final diameter of 25 mm. The investigation of the sample after pre-sintering and subsequent swaging was performed by microscopic and microhardness analyses, as well as by tensile testing. The results have shown the elongation of tungsten grains to increase with strain. The strength of the material after swaging was more than double comparing to the original state.
This paper numerically and experimentally describes the influence of cold rotary swaging on a pre-sintered tungsten alloy. The finite element method was applied to describe infeed swaging of 30mm diameter circular bar with 30% reduction of cross-sectional area. The numerically studied results were distribution of strain, distribution of temperature, effective strain rate and material flow during a single pass. To validate the predicted results, experimental swaging of pre-sintered W-Ni-Co tungsten alloy was realized. The results of strain distribution were compared with results from microstructure analysis and distribution of microhardness along the cross section of the swaged sample. Results of mechanical testing showed higher microhardness in regions near the swaged surface. This fact corresponds to the distribution of strain predicted by numerical modeling.
The aim of the study is to determine the effect of metallic nano and microparticles entered into laminates with the epoxy resin matrix reinforced with fiberglass. The reference analysis showed that research in the field of composites focus on improving strength properties, including fatigue, resistance to impact, thermal and electrical conductivity and combustibility.
Most of the tests are carried out in standard laboratory conditions, whereas in reality these materials often work in the most adverse external conditions. The paper presents the results of epoxy resin laminates fatigue studies. The laminates were reinforced by fiberglass, modified with metallic powders of different granulation including nanopowders.
Particular attention was paid to the study of fatigue strength at low temperature and compare it with the results of standard tests. The tests were performed on a specially designed bench with a mechanical forcing variable load on samples in the form of sidely fixed bar. The bench was equpped with a thermal chamber that allows for the implementation of research at temperatures from - 40 ° C to + 60 ° C. Based on these results, the guideline was developed for the planning of more advenced experiments, the results of which will be the basis for the design of laminates operating at extremely low or elevated temperatures.
Searching light construction capable of carrying concentrated mechanical static load was the fundamental target of undertaken problem. There were presented the numerical simulation results of 3D skeleton casting with regular built of elementary cell. The simulations were realized using CATIA software with use of Advanced Meshing Tools module. As a skeleton’s material near-eutectic aluminum silicate alloy AlSi11 was used. The aim of the study was verification of the suitability of the regular geometry of elementary cells carrying mechanical loads (including stress) and deformation analysis of the model skeleton casting. The skeleton was tested for characteristic cell size of 20 mm and connectors diameter forming elementary cells equal to 6 mm. The value and the accumulation of localized regions of stress were shown that allows the precise modification of the skeleton macrostructure.