Shock-induced stacking fault pyramids in Ni/Al multilayers

Abstract

The formations of stacking fault tetrahedra in {111}fcc/{111}fcc multilayers have been studied extensively, but the researches related to {001}fcc/{001}fcc interfaces can rarely be found in the literature. Using molecular dynamics (MD) simulations, the shock-induced dislocation structure in Ni/Al multilayers was studied in this article, the stacking fault pyramids (SFPs) initiated from Ni/Al interface was firstly observed, and the corresponding mechanism was explored. It was shown that the Shockley partial dislocations dissociated from the rectangular misfit dislocations along Ni/Al interface are first emitted into the Al interlayer and subsequently intersect with each other to form SFPs. With the propagation of the shock front in the multilayers, two adjacent SFPs interact with each other and form Lomer-Cottrell locks. The dislocation sheet composed of SFPs and Lomer-Cottrell locks can act as a barrier to dislocation transmission. The effect of shock piston velocity on the nucleation site of dislocation was also studied. It was shown that dislocations would originate from the interface at a low piston speed (<1.1km/s), and appear at the shock front if the piston speed exceeds 1.2km/s.