Understanding creep behavior of polycrystalline TiAl alloys by molecular dynamics simulations

The effect of temperature and stress on the creep behavior of polycrystalline γ-TiAl alloys was investigated by molecular dynamics simulations to gain a detailed understanding of the deformation mechanism at the atomic level. The results demonstrated that the minimum creep rate exhibited an increase and the creep life showed a reduction as the creep temperature/stress increased. The creep deformation mechanism was dominated by dislocation slip under the creep temperature of 1100K and the stress of 1.2 GPa. The predominant dislocation slip mechanism underlying creep deformation were 1/6[2‾11] Shockley partial dislocations, extended dislocations, 1/6[01‾1‾] Stair-rod dislocation and 1/3[0 1‾0] Hirth dislocation. These dislocations movement were hindered by the lamellar interface and accumulated at the lamellar interface during creep. The trend of total dislocation density over time tended to increase firstly and then decrease when the creep temperature was 1100K, 1300K, and 1500K, while the density of sessile dislocations exhibited fluctuations over time at low temperature of 900K. Finally, the evolution of shear strain and atomic mobility during creep under different creep temperature/stress was analyzed in detail.