In situ observations and crystallographic analysis of martensitic transformation in steel

The development of a martensitic structure in a low-carbon and low-alloy steel was characterized using in situ confocal laser microscopy, high-speed photography and crystallographic analysis, including the nature of variant selection. The initial stage of transformation involves the partitioning of the austenite grain into packets, after which the rate of transformation is gradual. The crystallographic orientation of the plates that form is not random, but involves selection determined by the relationship between the shape deformation direction and the free surface. The vicinity of austenite grain and twin boundaries, and martensite/austenite interfaces also affect variant selection.