Effects of isothermal bainite temperature on properties of CMnAl-TRIP cold-rolled steel sheets

CMnAl-TRIP steel contained copper and phosphorus was annealed at 820℃ for 2min and then isothermally treated at 450℃ and 400℃ for different time.The effects of the isothermal bainite temperature(IBT) on microstructure,mechanical properties and strain-induced martensite transformation of retained austenite were investigated.The results show that excellent mechanical properties combined with good ductility can be obtained.The better mechanical properties of the specimen isotherally heat treated at 450℃ was obtained.The lower total martensite transformation ratio together with the lower n value as well as lower uniform elongation and total elongation are appeared for the specimens heat treated at 400℃,in which the carbon content of retained austenite is higher.