The mechanism of low-temperature deformation in a fracture process of L12 Ni3Al was studied by molecular dynamic simulations. Due to the unstable stacking energy, the [0¯11] super-dislocation was dissociated into partial dislocations separated by a stacking fault. The simulation results showed that when the crack speed was larger than a critical speed, the Shockley partial dislocations would break forth from both the crack tip and the vicinity of the crack tip; subsequently the super intrinsic stacking faults were formed on adjacent {111} planes, while super extrinsic stacking faults and twinning also occurred. The simulation results suggested that, at low temperatures, ductile fracture in L12 Ni3Al was accompanied by twinning, which was produced by super-intrinsic stacking faults formed on adjacent {111} planes.

Dislocation Formation and Twinning from the Crack Tip in Ni3Al - Molecular Dynamics Simulations. Xie, H.X., Wang, C.Y., Yu, T., Du, J.P.: Chinese Physics B, 2009, 18[1], 251-8