Enhanced TRIP effect in a lean alloy steel treated by a ‘disturbed’ bainitic austempering process

Abstract

A novel isothermal bainitic transformation combined with quenching and partitioning (i.e. ‘disturbed’ bainitic austempering) process was employed in an Mn–Si–Cr–C low-alloyed steel to reduce the fraction and size of the blocky martensite/austenite (M/A) islands; the M/A islands that are inevitably formed during the conventional bainitic austempering process are coarse and undesirable for property optimization. Owing to a novel heat treatment, an enhanced combination of strength and ductility was achieved (e.g. ultimate strength, ∼1445 MPa; total elongation, ∼28%). A pronounced TRIP effect of the refined retained austenite contributes a lot to the overall improvement.