Dislocation formation and twinning from the crack tip in Ni3Al: molecular dynamics simulations

The mechanism of low-temperature deformation in a fracture process of L1(2) Ni3Al is studied by molecular dynamic simulations. Owing to the unstable stacking energy, the [0 (1) over bar1] superdislocation is dissociated into partial dislocations separated by a stacking fault. The simulation results show that when the crack speed is larger than a critical speed, the Shockley partial dislocations will break forth from both the crack tip and the vicinity of the crack tip; subsequently the super intrinsic stacking faults are formed in adjacent {111} planes, meanwhile the super extrinsic stacking faults and twinning also occur. Our simulation results suggest that at low temperatures the ductile fracture in L1(2) Ni3Al is accompanied by twinning, which is produced by super-intrinsic stacking faults formed in adjacent {111} planes.