Microscopic mechanism for the effect of temperature on impact resistance of polycrystalline γ-TiAl alloys:A molecular dynamics study

Polycrystalline γ-TiAl alloy is an excellent high-temperature material. To investigate the effect of initial temperature on the impact resistance of γ-TiAl alloys, this work employs molecular dynamics simulations to analyze the material responses under varying initial temperatures and impact velocities. The study focuses on three aspects: internal stress, microstructural evolution and dislocation movement. The results show that plastic deformation in γ-TiAl alloys is induced by both slip-induced plasticity and twinning-induced plasticity. When the initial temperature exceeds 780K, the alloy's plasticity and ductility decrease, and the also decreases with increasing temperature. The sudden reduction in the density of stair-rod and Hirth dislocations at temperatures above 780K is identified as a key factor contributing to the alloy's inadequate strength at high temperatures. Spalling occurs at grain boundaries, and the strength for spalling generally decreases with increasing initial temperature, although the change is relatively small below 780K. This work clarifies the micro-mechanisms of the mechanical responses of γ-TiAl alloys under impact loading, providing theoretical guidance for the impact-resistant design of high-performance polycrystalline γ-TiAl alloys.