Experimental and theoretical analysis of multiphase microstructure in a newly designed MnSiCrC quenched and partitioned steel to promote bainitic transformation: The significant impact on mechanical properties

Multiphase microstructure with carbide-free bainite, martensite and a small amount of film-like retained austenite was obtained in a new Mn-Si-Cr-C steel, designed to promote bainite transformation. The microstructural constituents were studied by a combination of electron microscopy, x-ray diffraction, dilatometry and high temperature laser confocal microscopy. A critical analysis of experimental data and theoretical analysis underscored that the austenite stability is enhanced by bainitic transformation, during quenching and partitioning process, besides carbon partitioning. The nucleation of bainite divided the untransformed austenite and refined the grain size of retained austenite, benefiting the mechanical properties, especially low temperature toughness.