Lath martensite substructure evolution in low-carbon microalloyed steels

Abstract Lath martensite substructures in as-quenched plain carbon steels exhibit dislocation-like contrast the transmission electron microscope. More recent observations reported internal twins and nanoscale auto-tempered intra-lath carbides as additional lath ultra-low-C binary Fe–C steels. Modern microalloyed often have similar ultra-low C contents besides microalloying elements like Ti, Nb or V and, more recently, Mo, to achieve high strength, toughness weldability. Nonetheless, little is known about substructure evolution state of This study investigates hierarchical post-quenching NbMo with 0.1 wt% C. Hierarchical microstructure characterization was done using scanning microscopy, backscatter diffraction methods including parent grain reconstructions MTEX. Thermokinetic simulations MatCalc determine carbide during auto-tempering were corroborated site-specific microscopy. Mo addition led lowering start temperature, yet steel showed a finer microstructure. Finer laths in-lath dislocations, short long twins, boundary decoration found steel. Conversely, wider, frequent precipitates vicinity without twins.