Effect of strain rate on nanocrystalline surface formation in controlled ball impact process in AISI 304 SS

Strain rate during severe plastic forming processes affects the grain size formation. Nanocrystalline grain size formation at and near the surface in stainless steel, AISI304, during the controlled ball impact process carried out at a high strain rate are reported. High strain rate exerted by using a small diameter ball resulted in the formation of grains of size ~ 80 nm on the surface. The peening coverage and surface roughness depend on the sample traveling velocity for a given ball diameter and impact velocity.