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.