High-temperature stability in Ti-based MAX phases: vacancy effects on mechanical properties

초록

Tin+1AlCn MAX phases are of interest due to their high-temperature mechanical properties. In this study, we investigated their structural and mechanical properties up to 2000 K using molecular dynamics (MD) tensile simulations and density functional theory (DFT) calculations, focusing on the effect of vacancies. The presence of up to 12.5% Al vacancies reduced the vertical Young's modulus by only 12.59% and left the UTS almost unchanged, demonstrating considerable mechanical robustness. In contrast, the same concentration of Ti vacancies degraded the Young's modulus by 40.7% at 2000 K. Electron localization function (ELF) analysis confirmed that the mechanical properties are dominated by strong Ti-C covalent bonds, which are not weakened by Al vacancies. In comparison to B1-type TiC, whose Young's modulus decreases by similar to 32% at 2000 K, Tin+1AlCn retains over 88% of its room-temperature vertical Young's modulus. This work provides a theoretical basis for considering Tin+1AlCn MAX phases as potential high-temperature structural materials.

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