Structure properties of AlSi7Mg/SiC composite produced by stir casting method

The paper presents the structure studies on composites of aluminum alloy matrix with addition of silicon carbide phase (from 5 to 15 vol.% SiC and 10 vol.% SiC + 10 vol.% graphite) obtained by the stir casting method. The aim of this work is to determine the influence of the SiC content and electrical discharge machining processes on the phase composition, microstructure, and values of residual stresses. In order to determine the heterogeneity of the obtained materials, the X-ray diffraction analysis was performed in different sample orientations to the direction of the X-ray beam (perpendicular and parallel), using different geometries (the Bragg-Brentano and grazing incident X-ray diffraction). This work presents the results of the residual stress analysis in the tested composites generated by various content of SiC additives. Residual stresses were determined by both of the ın²ψ and g-ın²ψ X-ray methods. Obtained results shown the significant gradient of residual stress in all cases

Presence of Oxygen in Ti-Al-C MAX Phases-Based Materials and their Stability in Oxidizing Environment at Elevated Temperatures

International audienceThe Ti3AlC2-, (Ti,Nb)3AlC2- and Ti2AlC-based materials turned out to be more resistant than Crofer JDAsteel in oxidizing atmosphere as 1000 h long tests at 600◦C have shown. But the amounts of oxygen absorbed bythe materials during testing were different. The Ti2AlC-based material demonstrated the lowest oxygen uptake,(Ti,Nb)3AlC2-based absorbed a somewhat higher amount and the highest amount was absorbed by Ti3AlC2-basedmaterial. Scanning electron microscopy and the Auger study witnessed that amounts of oxygen in the MAXphases before the exposure in air were as well different: the approximate stoichiometries of the matrix phases ofmaterials were Ti3.1−3.2AlC2−2.2, Ti1.9−4Nb0.06−0.1AlC1.6−2.2O0.1−1.2and Ti2.3−3.6AlC1−1.9O0.2−0.6, respectively.The higher amount of oxygen present in the MAX phase structures may be the reason for higher resistanceto oxidation during long-term heating in air at elevated temperature. The studied materials demonstrated highstabilities in hydrogen atmosphere as well. The bending strength of the Ti3AlC2- and (Ti,Nb)3AlC2-based materialsafter keeping at 600◦C in air and hydrogen increased by 10–15%, but the highest absolute value of bending strengthbefore and after being kept in air and hydrogen demonstrated the Ti2AlC-based material (about 590 MPa)

Presence of Oxygen in Ti-Al-C MAX Phases-Based Materials and their Stability in Oxidizing Environment at Elevated Temperatures

The Ti₃AlC₂-, (Ti,Nb)₃AlC₂- and Ti₂AlC-based materials turned out to be more resistant than Crofer JDA steel in oxidizing atmosphere as 1000 h long tests at 600°C have shown. But the amounts of oxygen absorbed by the materials during testing were different. The Ti₂AlC-based material demonstrated the lowest oxygen uptake, (Ti,Nb)₃AlC₂-based absorbed a somewhat higher amount and the highest amount was absorbed by Ti₃AlC₂-based material. Scanning electron microscopy and the Auger study witnessed that amounts of oxygen in the MAX phases before the exposure in air were as well different: the approximate stoichiometries of the matrix phases of materials were Ti_{3.1-3.2}AlC_{2-2.2}, Ti_{1.9-4}Nb_{0.06-0.1}AlC_{1.6-2.2}O_{0.1-1.2} and Ti_{2.3-3.6}AlC_{1-1.9}O_{0.2-0.6}, respectively. The higher amount of oxygen present in the MAX phase structures may be the reason for higher resistance to oxidation during long-term heating in air at elevated temperature. The studied materials demonstrated high stabilities in hydrogen atmosphere as well. The bending strength of the Ti₃AlC₂- and (Ti,Nb)₃AlC₂-based materials after keeping at 600°C in air and hydrogen increased by 10-15%, but the highest absolute value of bending strength before and after being kept in air and hydrogen demonstrated the Ti₂AlC-based material (about 590 MPa)