Achievement of martensite strengthening in titanium alloy thin-walled components via non-equilibrium hot stamping

The hot stamping using cold die technology demonstrates great advantages in improving the forming efficiency of titanium alloy thin-walled components. Martensite has been widely employed to strengthen steels, yet few applications were reported in titanium alloys. The main reason is that the martensite microstructure embrittles titanium alloys easily. In this paper, the nonequilibrium hot stamping technology is proposed for titanium alloys to solve the strength-ductility trade-off caused by martensite microstructure. Rapid heating is used to control phase transformation and grain growth during the short-time heating and obtain non-equilibrium microstructure. Non-equilibrium hot stamping experiments of the Ti-6Al-4V alloy were carried out to validate the feasibility. Results show that the rapid heating in the single β-phase region could avoid overgrowth of β grains and lead to the formation of fully fine martensite after water quenching. An Ω-shaped component with fully martensite microstructure were successfully formed by non-equilibrium hot stamping technology. The formed component has a maximum tensile strength of 1153.9 MPa, with a total elongation of 8.0% at room temperature, and the tensile strength is 13.0% higher than that of the as-received sheet.