2018 Volume 104 Issue 6 Pages 331-337
Hot-stamping process is widely applied to coated steel sheets including galvannealed steel sheets (GA) to produce high-strength automobile components. In this study, we investigated the structural changes in galvannealed coating during hot-stamping heating. It was revealed that the original δ1 phase decomposed to the Γ phase and Zn liquid above the peritectic temperature of the δ1 phase, then the Γ phase further decomposed to the Fe-Zn solid-solution and Zn liquid above the peritectic temperature of the Γ phase, and finally the coating changed to a single phase of the Fe-Zn solid-solution. The series of structural changes in GA coating can be explained with the Fe-Zn binary phase diagram.