Comparative Study of Hardening Mechanisms During Aging of a 304 Stainless Steel Containing α′-Martensite

Strain aging and hardening behaviors of a 304 stainless steel containing deformation-induced martensite were investigated by examining mechanical properties and microstructural evolution for different aging temperature and time. Introduced age hardening mechanisms of a cold rolled 304 stainless steel were the additional formation of α′-martensite, hardening of α′-martensite, and hardening of deformed austenite. The increased amount of α′-martensite at an aging temperature of 450 °C confirmed the additional formation of α′-martensite as a hardening mechanism in a cold rolled 304 stainless steel. Additionally, the increased hardness in both α′-martensite and austenite phases with aging temperature proved that hardening of both α′-martensite and austenite phases would be effective as hardening mechanisms in cold rolled and aged 304 stainless steels. The results suggested that among hardening mechanisms, hardening of an α′-martensite phase, including the diffusion of interstitial solute carbon atoms to dislocations and the precipitation of fine carbide particles would become a major hardening mechanism during aging of cold rolled 304 stainless steels.