Closed and open-ended stacking fault tetrahedra formation along the interfaces of Cu–Al nanolayered metals

Abstract

Stacking fault tetrahedra (SFTs) are volume defects that typically form by the clustering of vacancies in face-centred cubic (FCC) metals. Here, we report a dislocation-based mechanism of SFT formation initiated from the semi-coherent interfaces of Cu–Al nanoscale multilayered metals subjected to out-of-plane tension. Our molecular dynamics simulations show that Shockley partials are first emitted into the Cu interlayers from the dissociated misfit dislocations along the Cu–Al interface and interact to form SFTs above the triangular intrinsic stacking faults along the interface. Under further deformation, Shockley partials are also emitted into the Al interlayers and interact to form SFTs above the triangular FCC planes along the interface. The resulting dislocation structure comprises closed SFTs within the Cu interlayers which are tied across the Cu–Al interfaces to open-ended SFTs within the Al interlayers. This unique plastic deformation mechanism results in considerable strain hardening of the Cu–Al nanolayered metal, which achieves its highest tensile strength at a critical interlayer thickness of ~4 nm corresponding to the highest possible density of complete SFTs within the nanolayer structure.

Keywords:

• plasticity
• stacking fault tetrahedra
• nanolayered metals
• dislocation
• molecular dynamics

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by AFOSR [grant number FA9550-15-1-0117]; as well as computational time provided by TACC [grant number TG-MSS130007]; the Blue Waters sustained-petascale computing project which is supported by the National Science Foundation [grant number OCI-0725070], [grant number ACI-1238993] and the state of Illinois. Blue Waters is a joint effort of the University of Illinois at Urbana-Champaign and its National Center for Supercomputing Applications.