First-principles study on structural, elastic and thermal properties of gamma-TiAl and alpha(2)-Ti3Al phases in TiAl-based alloy under high pressure

摘要

The structural, elastic and thermal properties of gamma-TiAl and alpha(2)-Ti3Al phases in the TiAl-based alloy under pressure were reported using CASTEP program based on the density functional theory. The calculated equilibrium parameters and elastic constants are in good agreement with experimental and the available theoretical data. The results indicate that under the same pressure, the alpha(2) phase in the direction along a-axis is easier to be compressed than the gamma phase, while the compression along c-axis of gamma phase is larger than that of alpha(2) phase; when the pressure is below 20 GPa, both the two phases are elastically stable, but the gamma phase have higher shear modulus and Youngs modulus, and the alpha(2) phase has better ductility and plasticity. Debye temperature, bulk modulus, thermal expansion coefficient and heat capacity of the gamma phase and alpha(2) phase under high pressure and high temperature were also successfully calculated and compared using the quasi-harmonic Debye model in the present work.