Effects of alloying element segregation bands on impact response of a 304 stainless steel

Abstract

The influence of segregation bands of alloying elements Cr and Ni on impact response of a 304 stainless steel is investigated under high strain rate impact loading with a single-stage gas gun. Free-surface velocity histories are measured to evaluate the mechanical properties. The Hugoniot elastic limits are 1.0–1.1 GPa, and the spall strengths are 2.1–2.4 GPa for the impact velocities explored. Oriented segregation bands induce negligible anisotropy in the Hugoniot elastic limit (dynamic yield stress) and spall strength. Scanning electron microscopy analyses show that microvoids tend to coalesce along the segregation bands, regardless of the loading direction, indicating segregation bands or the interfaces between segregation bands and matrix are the weakest nucleation sites. The fracture strength is dominated by the segregation bands, and thus independent of strain rate and peak stress. However, the damage degree is related to both peak stress and segregation band orientation. When the peak stress is lower than 5 GPa, damage degree is independent of the loading direction. At higher peak stresses, the damage degree is larger for impact direction aligned along segregation bands.