High-speed Tensile Deformation Behavior of 1 GPa-grade TRIP-aided Multi-phase Steels

High-speed deformation behavior and strain rate dependency of mechanical properties of 1 GPa-grade TRIP-aided multi-phase (TRIP) steels were studied. The strain rate range in this study was between 3.3 × 10−6 and 103 s−1, and the effect of retained austenite (γR) shapes on TRIP effect in the 1 GPa-grade TRIP steel was also focused on. The effects of strain rate on tensile strength and flow stress in the TRIP steels were small whereas that on uniform elongation was large. The strain rate dependencies of tensile strength and uniform elongation in the TRIP steels were more closely to those of the metastable austenitic stainless steels than the conventional TRIP and dual-phase steels. The 1 GPa-grade TRIP steel with the γR shape of needle-like showed better tensile properties and absorbed energy in the present strain rate range. The volume fraction of γR more than 20% and the matrix microstructure of martensite seem to be important factors in the high-strength TRIP steels.