Investigate on ultrahigh-strength TRIP-aided autosteel plate under the framework of ICME

Abstract

A novel low-carbon (C) low-alloy transformation-induced plasticity (TRIP) steel with a nominal composition of Fe-0.3C-1.9Mn-1.0Si-0.7Al wt.% was successfully designed by combining high-throughput thermodynamic and kinetic calculations and feature engineering based on the Integrated Computing Materials Engineering (ICME) framework. The designed TRIP steel was subjected to a series of two-stage heat treatments according to the target intercritical annealing temperature determined by estimation in an attempt to optimize phase constituents to obtain an ideal strength-plasticity balance. After annealing at 780 °C, the ultimate tensile strength (UTS), total elongation (TEL) and the product of strength and elongation (PSE) of the experimental steel can reach ∼980 MPa, ∼30% and ∼30 GPa•% respectively, because of the appropriate phase fraction and size of retained austenite (RA). Annealing at 820 °C, when the isothermal bainitic transformation (IBT) temperature is low, the short distance diffusion of C made it enriched in a small region, the stability of different RA grains varied greatly, which was not conducive to ensure stable and continuous TRIP effect. Moreover, by evaluation of the effect multiphase on yield strength (YS) and UTS, the presence of more bainite led to samples having higher tensile strength but deteriorated their plasticity.