Detailed deformation behaviour analysis of DP steels at warm forming temperatures via warm tensile tests

DP advanced high strength steels (AHSSs) have an important place in automotive industry for producing parts like B-pillars, door rings, etc. However, the excellent strength of AHSSs increases the issues related to their formability. Therefore, it is necessary to implement new forming processes to fully utilize the excellent properties of DP steels in more complex parts. In this study, the formability of DP steels (DP600, DP800) and their deformation behaviour at warm forming temperatures have been investigated by a series of tensile tests conducted at elevated temperatures (75, 175, 275, 375°C) and two different strain rates (0.05, 0.005 s-1). To understand the deformation behaviour thoroughly, both instantaneous and average strain hardening – n and strain rate sensitivity – m values, the change in the hardening capacity and the microstructure have been analyzed. The results have shown that the formability of DP steels at 375°C is more favourable as compared at room temperature.