First and third generations of advanced high-strength steels in a FeCrNiBSi system

Abstract

Three different solidification routes (slow, accelerated and fast) and a two-step heat treatment process were applied to a FeCrNiBSi alloy system to introduce new candidates for advanced high-strength steels (AHSSs). The evolution of the microstructure after hot roll, heat treatment, and tensile deformation was characterized using optical and electron microscopy techniques, as well as hardness and room temperature uniaxial tensile tests. The increase in the initial strain-hardening rate (strain incompatibility of microstructure components) due to grain refinement as a consequence of fast casting cooling rate results in higher mechanical properties in fast-cooling specimens with a formability index of 18.00–37.80 GPa%. Deformation-induced precipitation in the as-rolled fast-cooling specimen and transformation-induced plasticity, microband formation, and austenite grain rotation in the heat-treated fast-cooling specimen are the main dissipation energy mechanisms. The heat-treated accelerated-cooling and slow-cooling specimens with formability index of 4.75–25.50 and 2.34–14.60 GPa%, respectively, are competitive with transformation-induced plasticity, dual-phase, and complex-phase AHSSs.