New crystallography insights of retained austenite transformation in an intercritical annealed quenching and partitioning steel

Abstract We studied the transformation of retained austenite in an intercritical annealing quenching and partitioning steel in aspect of mechanically induced martensite variant selection. The martensitic transformation process was characterized through the interrupted tensile tests plus ex-situ electron backscattering diffraction measurements. We have observed two kinds of retained austenite, the larger equiaxed austenite and the finer lamellar austenite. Results show that the variant selection becomes stronger as the retained austenite grain size decreasing. Equiaxed retained austenite tends to transform into a certain variant with close orientation to adjacent ferrite. In this case, phase transformation in specific grains could occur earlier under stress, regardless of the grain size.