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Mechanical properties of WN43 magnesium alloy prepared by spark plasma sintering
Knapek, Michal ; Minárik, P. ; Greš, A. ; Zemková, M. ; Cinert, Jakub ; Král, R.
The spark plasma sintering (SPS) method was used to prepare bulk materials form WN43 magnesium alloy atomized powder. Compression tests were carried out in order to investigate the effect of different sintering regimes (10 min at 400, 450, or 500 degrees C) on the mechanical properties of the material. Furthermore, complementary in-situ acoustic emission (AE) recording was employed to reveal the dynamics of deformation processes during compression. It was shown that by increasing the sintering temperature, the ultimate compressive strength and ductility were significantly improved. The AE data and microstructure observations suggest that pronounced twin nucleation takes place around the yield point whereas twin growth and dislocation activity are the dominant deformation mechanisms in the later stages of deformation.
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Effect of sintering temperature on microstructure and mechanical properties of AE42 magnesium alloy prepared by spark plasma sintering
Minárik, P. ; Lukáč, František ; Cinert, Jakub ; Šašek, S. ; Král, R.
Magnesium alloy AE42 was prepared by powder metallurgy technique of spark plasma sintering. The effect of sintering parameters, particularly sintering temperature, on the microstructure and mechanical strength was investigated. The gas-atomized powder was sintered at four temperatures in the temperature range of 400-550 °C. It was found that mechanical strength of the sintered samples was significantly affected by several microstructural features. Application of relatively high load during sintering caused deformation of the individual particles and consequent recrystallization depending on the processing temperature resulted in the release of internal strain and in grain growth. As a result, the evolution of the mechanical strength as a function of the sintering temperature was significantly affected by residual stress, grain size and coarsening of secondary phase particles.
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The investigation of an Al-Zr-Ti alloy prepared by spark plasma sintering of atomized powder
Molnárová, O. ; Málek, P. ; Lukáč, František ; Chráska, Tomáš ; Cinert, Jakub
The microstructure and mechanical properties of a powder metallurgical Al-Zr-Ti alloy was studied. Fine powder with a typical size below 50 ?m was prepared by gas atomization. The smallest powder particles with a diameter below 10 ?m exhibited a segregation free microstructure. Larger droplets were found to contain intermetallic particles rich in Zr and Ti. The gas atomized powder was consolidated by spark plasma sintering (SPS) at various temperatures ranging from 450 to 550 °C. During SPS the materials microstructure remained nearly unchanged and a fine grain size between 2 and 3 ?m was observed. All SPS samples exhibited a microhardness of around 90 HV. The annealing (1 h, 500 °C) of the sample sintered at the highest temperature (550 °C) resulted in a decrease of microhardness to 75 HV as a result of changes in the phase composition, the fine grain size was retained. Natural aging at room temperature was not observed.
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THE INVESTIGATION OF AN Al7075 ALLOY PREPARED BY SPARK PLASMA SINTERING OF MILLED POWDERS
Molnárová, O. ; Málek, P. ; Nemeth, G. ; Kozlík, J. ; Lukáč, František ; Chráska, Tomáš ; Cinert, Jakub
Atomized powder of an Al7075 alloy was high energy ball milled at room and cryogenic temperatures and compacted by spark plasma sintering (SPS) method. The influence of processing parameters on phase composition and microstructure was studied by X-ray diffraction, 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 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 220 HV. 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. A drop in microhardness to 118HV was observed after SPS, predominantly due to a release of introduced deformation energy.
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