Enabling strong and formable advanced high-strength steels through inherited homogeneous microstructure

Abstract

Fabricating quenching and partitioning (Q&P) steels with less mechanical heterogeneity among phases is crucial for achieving balanced strength and formability. In the present study, we demonstrate a strategy for fine-tuning the microstructural inheritance effect to optimize the final microstructure. This approach involves a rapid cooling and tempering step after hot rolling to template an initial microstructure with uniformly distributed ferrite laths. The final microstructure contains a higher volume fraction of primary martensite and stable retained austenite, leading to enhancement in both strength and ductility. The templating method also eliminates bulky ferrite and significantly reduces strain localization, as demonstrated by microscopic digital image correlation (μ-DIC). The templated final microstructure not only achieves higher yield strength compared to existing Q&P980 steels, but also exhibits simultaneous improvement in elongation and stretch-flangeability. Our findings suggest that it is essential to consider and leverage the inheritance effect to optimize products with long processing chains.