Enhancing both strength and ductility of low-alloy transformation-induced plasticity steel via hierarchical lamellar structure

In this paper, martensite-to-austenite reversion during intercritical annealing was applied to a conventional low-alloy transformation-induced plasticity steel to form reverted austenite, which was followed by austempering to form bainite, and hence the resulting microstructures and mechanical properties were investigated. The obtained microstructure is composed of alternating lamellae of intercritical ferrite and reverted austenite on microscale, with the latter consisting of bainitic ferrite laths and retained austenite films on nanoscale. This unique microstructure exhibits excellent strength–ductility combinations, which surpass those of conventional polygonal blocky-structured counterparts, providing a strategy for developing high-performance structural materials at low production cost.