2021 Volume 107 Issue 11 Pages 968-976
The effect of deformation temperature on the mechanical properties of 1-GPa-grade TRIP steels with different retained austenite (γR) morphologies was studied. The temperature dependence on the deformation-induced martensitic transformation behavior was also investigated. The uniform elongation below room temperature was relatively large in the needle-like γR steel, whereas the tensile strength at each temperature was almost the same as it was independent of the γR morphology. The better tensile strength–uniform elongation balance was obtained at 373 K for the needle-like γR steel and at 473 K for blocky γR one. The mechanical stability of γR was higher in the needle-like γR steel, according to the x-ray diffraction experiments. γR was mechanically stable with increasing temperature, but its volume fraction decreased at temperatures above 473 K because of the deformation-induced bainitic transformation. In this paper, the quantitative conditions of deformation-induced transformation to obtain better uniform elongation in the 1-GPa-grade TRIP steels are summarized from the viewpoints of the volume fraction of deformation-induced martensite and the transformation rate.