Planar fault assisted dynamic recrystallization in copper during high-velocity impacts

Dynamic recrystallization (DRX) is a widely observed phenomenon in metals and alloys during hot deformation. However, a comprehensive understanding of the mechanisms and microstructural evolution of DRX at extremely high strain rates is still lacking. In this study, we present a new mechanism, termed planar fault-assisted dynamic recrystallization (pfDRX), which was identified by simulating the cold spray of copper (Cu) at high strain rates using molecular dynamics. Our findings indicate that planar faults, such as nanotwins, stacking faults, hexagonal close-packed martensites, and local slip, play a dominant role in the initial deformation of Cu during high velocity impacts in columnar-like quasi-two-dimensional samples where deformations are primarily limited to in-plane slip. Furthermore, subsequent slip events interact with pre-existing planar faults, triggering the formation of new grains via a common interaction-amorphization-nucleation-growth pfDRX mechanism. We systematically varied temperature and strain rates to determine the optimal conditions for pfDRX. This study offers valuable insights into novel DRX mechanisms in face-centered cubic metals at high strain rates and provides guidance for future experimental research.