Strain induced martensite formation and its effect on strain hardening behavior in the cold drawn 304 austenitic stainless steels

SIM in the present cold drawn austenitic stainless steels, AISI 304 and AISI 304/Cu, nucleates mainly at the intersections of the mechanical twins rather than ε-martensite. The present results are attributed to the suppression of the formation of ε-martensite due to the increase of stacking fault energy which arise from the heat generated during high speed drawing and, for AISI 304/Cu, the additional effect of Cu additions. The strain hardening behavior of the present steels is strongly related to the microstructural evolution accompanied by SIM transformation: mechanical twinning at small strains, the formation and the growth of α′-martensite at intermediate strains, and plastic deformation and concurrent dynamic recovery in SIM at large strains.