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Description
The TRIP steels have multiple phase structures including ferrite, bainite and retained austenite accompanied by a small quantity of martensite. The retained austenite and its morphology are considered as the most important phase in microstructure of TRIP steels which it leads to improvement of formability and strength of these steels. In this study, considered the effects of heat treatment parameters on mechanical properties of hot-rolled TRIP steel. For this purpose, a TRIP steel containing Si and Mn after thermo-mechanical treatment and critical annealing in 810°C, was austempered in temperature range of 340-460°C at different holding times to be investigated the effect of volume fraction of retained austenite and its morphology on improvement of mechanical properties. The results showed that increasing of the volume fraction of retained austenite considerably improve the strength and ductility of this steel. The temperature of 400°C and the holding time of 6 min is the optimum austempering condition to be obtained the highest mechanical properties.