Flash annealing yields a 1.5 GPa low-carbon martensitic/bainitic steel with high ductility and toughness

Low-carbon martensitic/bainitic (LCM/B) steels typically exhibit strengths below 1 GPa and are susceptible to tempering embrittlement. This work proposed a flash annealing (FA) process as an alternative to conventional tempering, which enabled the achievement of 1.5 GPa-grade Ni- and Al-alloyed LCM/B steels with a superior combination of ductility and toughness. FA at intercritical temperature results in a high density of nano-sized B2-Ni(Al, Fe) precipitates, along with θ-Fe 3 C carbides. Furthermore, FA effectively refines prior austenite grains as well as packet and block sizes, all of which contribute to the enhanced strength and toughness. The resulting high-density B2-Ni(Al, Fe) precipitates and grain refinement lead to an ultrahigh tensile strength of approximately 1.5 GPa, a total elongation exceeding 12%, and excellent impact toughness of no