Grain coarsening behaviour under small plastic strain in hot working of BS 304S31 stainless steel

Abstract

Hot compression tests were conducted on an austenitic stainless steel, BS 304S31, to clarify the origin of the grain coarsening phenomenon that is observed for carbon steels deformed slightly at a high temperature. The grain size was measured after hot compression testing, and the distribution was compared with that of the equivalent plastic strain ϵ_eq calculated using a rigid plastic finite element analysis technique. Similarly to carbon steels, a clear band zone was observed, although in a different region, in the plane difined by working temperature and ϵ_eq. The adoption of a material without a phase transformation has provided strong evidence supporting the hypothesis presented for carbon steels that the grain coarsening phenomenon is strain induced grain growth in the austenite region. A peculiar, staggered grain boundary was observed as the equivalent plastic strain approached the threshold value for the initiation of grain coarsening.