A wide variety of industrial applications require materials with high strength and ductility. Unfortunately, the strategies for increasing material strength tend to decrease ductility.

Professor Haiwen Luo and associate professor Bin Hu in our department cooperating with the University of Hong Kong and National Taiwan University developed a strategy to circumvent in an inexpensive, medium Mn steel. Warm rolling plus cold rolling followed by low-temperature tempering allowed developed steel with metastable austenite grains embedded in a highly dislocated martensite matrix. This deformed and partitioned (D&P) process produced dislocation hardening, but retained high ductility both through the glide of intensive mobile dislocations and by allowing us to control martensitic transformation.

Finally, the “Super Steel” with the ultrahigh yield strength of 2.2 GPa and total elongation of 16% was developed. Besides, this steel have low alloy cost comparing with the other existing ultrahigh strength steels. The D&P strategy should apply to any other alloy with deformation-induced martensitic transformation and provides a pathway for development of high strength, high ductility materials.

Paper link:https://science.sciencemag.org/content/357/6355/1029.abstract