Achieving superior strength and high ductility in AISI 304 austenitic stainless steel via asymmetric cold rolling

In this study, the microstructure-texture-mechanical properties relationships in AISI 304 austenitic stainless steel processed by asymmetric cold rolling investigated. With increasing the deformation, the number of twins and deformation-induced martensites including alpha' and epsilon increased. Interestingly, after 30% rolling, the volume fraction of martensite decreased from 47.34% to 32.69% due to the occurrence of recrystallization. Texture results indicated that after 30% and 40% deformation, the recrystallization texture increased. Two texture transitions from Goss to Brass at 30% deformation and from Copper to Brass at 40% strain observed. The Copper to Brass transition occurred in three distinct paths. The 40% rolled sample exhibited a quite high hardness of 448.3 HV due to the increasing strain hardening, mechanical twins, martensite phases, and grain refinement. The deformed samples exhibited strong anisotropy of hardness and the hardness on the RD-TD plane is higher than two other planes. The results showed a significant increase in yield (1203.2 MPa) and ultimate tensile (1229.2 MPa) strength in the 40% deformed samples with respect to the initial austenitic steel, while a considerable ductility (23.3%) remained. With increasing the rolling reduction from 10% to 40%, the diameter and depth of the dimples reduced and uniformity of dimples decreased. However, the fracture mode was ductile with sufficient plastic deformation before failure. Finally, with increasing the deformation, the number of striations and fine dimples increased due to the formation of more mechanical twins and fine grains, respectively.