Study on dynamic recrystallization-based microstructure evolution mechanism of 40Cr during strengthening grinding

Abstract

Grind-strengthening represents a novel surface modification process that combines a precision removal process of material and the strengthening function of surface modification. The high heat and severe plastic deformation (SPD) of the ground superficial layer can induce the phase transformation and dynamic recrystallization (DRX) grain refinement behavior. Consequently, the prediction and control of the ground superficial layer microstructure is of considerable significance to improve the wear resistance and fatigue resistance performance of parts. Firstly, the dynamic mechanical properties at high temperature and shock compression were tested by the split Hopkinson pressure bar (SHPB) experiment for 40Cr steel. The material's constitutive relations, critical strain and DRX model can be determined. Subsequently, the finite element (FE) method was proposed to predict the temperature and strain distribution of the ground strengthening layer. The DRX volume fraction and grain size of the ground superficial layer can be realized via Abaqus/explicit user subroutine VUHARD. Finally, a phenomenological simulation of the ground strengthening layer microstructure is realized utilizing the cellular automata (CA) method combined with FE analysis results. With the help of grind-strengthening experiments, the gradient distribution of grain refinement layer at different cutting depths is consistent with the prediction results. The proposed DRX and microstructure predicted model can provide theoretical support for the surface strengthening of steel grinding. The modification behavior of the gradient refinement induced by grind-strengthening has significant application potential in the fields of transmission parts such as gears and shafts.