Abstract: Molecular dynamics simulation was used to investigate the effect of hole defects on crack propagation of polycrystalline γ-TiAl alloy at different temperatures, hole locations and hole sizes. The results show that the polycrystalline γ-TiAl alloy with hole defect is of brittle cleavage fracture at 1-750 K, but of ductile creep fracture at 1000 K and 1200 K. The alloy is more likely to fail when the hole is located on the grain boundary and triple junction. Compared with the perfect crystal, the micropores increase the ductility of the polycrystalline γ-TiAl alloy. When the hole radius is larger than 1.0 nm, the yield stress and yield strain of the alloy decrease sharply, and the time of the alloy failure is advanced. The fracture mode is influenced by the hole size. Intergranular fracture occurs when the hole radius is less than or equal to 0.8 nm. When the hole radius is larger than 0.8 nm, the hole in the polycrystalline γ-TiAl alloy gradually expands and occupies the whole grain, and then transgranular fracture occurs.

Key words: molecular dynamics, polycrystalline γ-TiAl alloy, hole defect, stress-strain curve, fracture behavior