The current study investigated evolution of fine-scale microstructure in H13 steel additively manufactured by laser directed energy deposition. X-ray diffraction, scanning electron microscopy, and site specific transmission electron microscopy were employed for the analysis. A multiphysics, multi-layer, and multi-track computational process model in conjuncture with time-temperature-transformation diagram provided variation in temperature as a function of time along with the corresponding phase transition pathways. The additively produced H13 steel sample exhibited cellular solidification of austenite grains followed by its near complete transformation into ferrite/martensite. Fine-scale observations indicated the presence of precipitates rich with carbide forming elements at the cell boundaries and junctions. Site specific transmission electron microscopy revealed these precipitates to be Mo-V and Cr rich carbides. The matrix consisted of martensite as the main phase. Small pockets of retained austenite were detected within the martensitic matrix.
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