Hot-rolled and continuously cooled bainitic steel with good strength-elongation combination

The current work demonstrates the microstructural evolution and mechanical property evaluation of a newly designed steel composition after hot rolling in laboratory-scale rolling mill, followed by continuous cooling. The steel thus developed has typically about 80% carbide-free bainite; about 20% retained austenite and can deliver approximate to 1400MPa ultimate tensile strength along with more than 20% total elongation. The presence of ultra-fine bainite plates (approximate to 100-130nm thick) with high dislocation density was thought to be responsible for ultra-high strength. Excellent ductility at such strength level could be due to the presence of sufficient amount of retained austenite (approximate to 20%) thermally stable at room temperature but starts transforming to martensite during deformation exhibiting transformation-induced plasticity effect.