Three-dimensional morphology of coarse martensite formed in a low carbon steel

Despite the importance of understanding the true three-dimensional (3D) morphology, distribution, crystallography, and interconnectivity of solid-state precipitates and matrix grains, microstructural characterization prior to the last decade has usually been accomplished by methods that enable only two-dimensional (2D) observations. This paper presents new findings from a recent 3D microstructural. investigation of coarse martensite in a low carbon, high strength low alloy steel (HSLA-100). The results show that the true 3D shape of these martensite crystals is often significantly different from what is deduced based on 2D observations alone. In particular, a very coarse lath-like asymmetric wedge morphology with one small flat facet and one sharp edge was repeatedly observed by 3D reconstructions. A second more irregular or blocky morphology was also occasionally observed.