Influences of nanotwin volume fraction on the ballistic performance of coarse-grained metals

Coarse-grained (CG) metals strengthened by nanotwinned (NT) regions possess high strength and good ductility. As such, they are very suitable for applications in bullet-proof targets. Here, a numerical model based on the conventional theory of strain gradient plasticity and the Johnson–Cook failure criterion is employed to study the influences of volume fraction of NT regions on their ballistic performance. The results show that in general a relatively small twin spacing (4–10 nm) and a moderate volume fraction (7%–20%) will lead to excellent limit velocity and that the influences of volume fraction on limit displacement change with the category of impact processes.