Molecular dynamics simulations on shock induced plasticity and stacking fault of coherent {001} Ni/Ni3Al laminate composite

Abstract

Using molecular dynamics (MD) simulations, the shock induced plasticity and stacking fault of coherent {001} Ni/Ni3Al laminate composite based on the interfaces were studied in this work. Firstly, the influences of interfaces on shock wave propagation are studied. The results reveal “reflection-unloading” at the Ni-Ni3Al, but “reflection-loading” at the Ni3Al-Ni. Strong discontinuities of shock wave stress at the interfaces also are revealed, the discontinuities are correlated to the impedance mismatch and elastic-plastic properties of the two materials adjacent to the interfaces. Secondly, the dislocation activities and stacking faults in the Ni3Al layer were obtained through shock simulation of multilayer target, and the interfacial lattice mismatch was studied at the atomic level, the abnormal arrangement of the atomic layers on both sides of the interface was found. Thirdly, since atoms in different directions are not activated at the same time during shock, resulting in dislocation decomposition in two steps. The dislocation sheet composed of Lomer-Cottrell locks and Hirth locks can act as a barriers to dislocation transmission. The phase transition process induced by the shock was also studied. The result showed that the region where the dislocation lines are located first changed from fcc to bcc. With the slip extension of Shockley dislocations, bcc to hcp continued to occur in the stacking fault region.

Keywords

• Ni/Ni3Al
• Shock
• Plasticity
• Stacking fault
• Dislocation
• Phase transition