On the Factors Influencing the High Stretch–Flangeability of a Low-Density 1180 MPa Fe–Mn–Al–C–Nb Δ-Qp Steel

Low-density δ-quenching and partitioning (δ-QP) steels with excellent strength and ductility have been recently developed. However, there are still rare reports on the formability of δ-QP steels, which are critical for satisfying the manufacture of structural parts during the application in automotive industry. In the present work, an 1180 MPa Fe–Mn–Al–C–Nb δ-QP steel with a high ductility was adopted for the stretch–flangeability study. The δ-QP steel was developed by separated quenching and partitioning processes. A good hole expansion ratio (HER) of 34.9 ± 0.9