Temperature-dependent deformation processes in two-phase TiAl + Ti₃Al nano-polycrystalline alloys

Although deformation processes in single-phase nano-polycrystalline alloys at different temperatures are well described, the deformation mechanism in two-phase nano-polycrystalline alloys at different temperatures is still unclear. Here, the deformation behaviour of the two-phase TiAl+Ti₃Al nano-polycrystalline alloys is investigated at different temperatures by molecular dynamic simulation. For a comprehensive understanding of the processes, mechanical properties of the single-phase TiAl and Ti₃Al nano-polycrystalline alloys are explored as well. The results of numerical simulations indicate that temperature has a strong influence on the deformation mechanism of the alloys. When temperature is below 800 K, the critical grain size (~8.3 nm) becomes a dominant factor controlling the deformation process in the single-phase TiAl. In the two-phase TiAl+Ti₃Al nano-polycrystalline alloys, the motion of dislocations in the TiAl phase with the grain size smaller than the critical size dominates the deformation process. On the other hand, no obvious phenomena linked with the critical size occur in the Ti₃Al phase. Once the strain exceeds 18.0%, the dislocation emission is observed in the Ti₃Al grains. At high temperatures (≥800 K), in the two-phase nano-polycrystalline alloy, the deformation mechanism changes from the plastic deformation to the boundary slip and recrystallization.