Investigation on micro-mechanics properties of machined metamorphic layer based on crystal plasticity finite element method

Abstract

Surface materials endure significant mechanical and thermal loads during machining, leading to microstructural changes and the formation of metamorphic layers. These layers exhibit altered crystallographic characteristics, such as grain size, misorientation angles, and dislocation density, resulting in mechanical properties that differ from the bulk material. This study examines the microstructural evolution of the metamorphic layer using electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD). Based on microstructure characterization, a 3D reconstruction method was developed using a representative volume element (RVE). The crystal plasticity finite element method (CPFEM) was employed to establish the relationship between the microstructure and micromechanical properties, including microhardness, elastic modulus, and yield stress. The proposed method was validated by comparing simulation results with experimental data obtained from micro-pillar compression tests and nanoindentation tests. The results demonstrated a strong correlation in stress-strain curves, and the microhardness measurement error at indentation depths of 400 nm was less than 10 %.