Global and Local Formability of 3rd Generation Advanced High Strength Steels

The present work investigates the global and local formability of two third-generation Advanced High Strength Steels (AHSSs), a quenching & partitioning (Q&P) steel and a Medium Mn (MMn) steel with 1GPa strength. Third-generation Q&P and MMn steels are designed to overcome the limitations of first-generation AHSS grades by enhancing formability while maintaining high mechanical strength, thus enabling more efficient structural design and improved crash performance. Understanding their forming behaviour is essential to ensure their reliable use in complex sheet metal forming operations. In this study, the forming performance of a Q&P and a MMn steel is analysed through experimental procedures involving both in-plane deformation under various loading paths and hole expansion tests with different hole edge qualities, to evaluate their global and local formability. A first-generation Dual Phase (DP) steel is included in the analysis for comparison. The results demonstrate that 3rd Generation Q&P and MMn steels exhibit very good global formability, superior to conventional 1st Generation AHSSs. However, local formability, as evaluated by hole expansion capacity, can be severely compromised by edge manufacturing process. These findings contribute to a deeper understanding of the distinction between global and local formability in third-generation AHSS, offering insights to improve process robustness and support the industrial implementation of these steels in high-performance automotive components.