Dislocation density and grain size evolution in hard machining of H13 steel: numerical and experimental investigation

In this research, the microstructure evolution in the machined subsurface is numerically simulated through a developed multi-physics model applied to H13 hot work die steel. The multi-physics model based on dislocation density evolution is utilized to predict the change of grain size through finite element analysis by varying cutting parameters. In spite of the cutting conditions, the simulated grain size on the top-most machined surface is around 330 nm, and the machining-affected depth with refined grain varies in the range of 25–45 μm. In addition, the appeared periodical fluctuation of dislocation density and grain size in a wavy configuration induced by the generated serrated chip segments is revealed. The efficacy of the proposed finite element model is verified and the probable mechanism of grain refinement is demonstrated with the assistance of TEM observation, which in turn promotes the in-depth understanding of microstructure evolution during metal cutting.