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Microstructure and High-temperature Oxidation Behavior of Ti3AlC2/W Composites


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Using spark plasma sintering, Ti3AlC2/W composites were prepared at 1300°C. They contained “core-shell” microstructures in which a TixW1−x “shell” surrounded a W “core”, in a Ti3AlC2 matrix. The composite hardness increased with W addition, and the hardening effect is likely achieved by the TixW1−x interfacial layer providing strong bonding between Ti3AlC2 and W, and by the presence of hard W. Microstructural development during high-temperature oxidation of Ti3AlC2/W composites involves α-Al2O3 and rutile (TiO2) formation ≥1000°C and Al2TiO5 formation at ~1400°C while tungsten oxides appear to have volatilized above 800°C. Likely due to exaggerated, secondary grain growth of TiO2-doped alumina and the effect of W addition, fine (<1 μm) Al2O3 grains formed dense, anisomorphic laths on Ti3AlC2/5 wt%W surfaces ≥1200°C and coarsened to large (>5 μm), dense, TiO2-doped Al2O3 clusters on Ti3AlC2/10 wt%W surfaces ≥1400°C. W potentially affects the oxidation behavior of Ti3AlC2/W composites beneficially by causing formation of TixW1−x thus altering the defect structure of Ti3AlC2, resulting in Al having a higher activity and by changing the scale morphology by forming dense Al2O3 laths in a thinner oxide coating, and detrimentally through release of volatile tungsten oxides generating cavities in the oxide scale. For Ti3AlC2/5 wt%W oxidation, the former beneficial effects appear to dominate over the latter detrimental effect.

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