Analysis of crystal structure transition of polycrystalline 3C-SiC in nanocrystalline grinding based on molecular dynamics simulation

Abstract

In order to study the grain/grain boundary crossing mechanism of polycrystalline 3C-SiC materials under nano-grinding, molecular dynamics(MD) method was used to simulate the grinding process of polycrystalline 3C-SiC materials under diamond abrasive particles. Through the coupling method of Voronoi construction of polycrystalline 3C-SiC workpiece model and MD construction process, the nano-grinding process of polycrystalline 3C-SiC material was established, the potential function field parameters were optimized, and the residual stress in polycrystalline 3C-SiC was eliminated. The energy transition equation is modified to reduce the time for the system to enter dynamic equilibrium. The crystal structure and dislocation generation of polycrystalline 3C-SiC were analyzed by post-processing methods such as defect analysis and crystal structure recognition. The results found that: there are cubic lattice, simple cubic lattice, hexagonal lattice and graphene mechanism type atoms at the grain boundary. During the machining process, the cubic lattice type atoms are converted to other types atoms, and other types structure atoms are converted to each other. The internal structure atoms of grains are converted to the grain boundary structure atoms during the machining process, and the crystal atoms near the grain boundary have low structural stability. The grinding force mainly acts on the forward direction and just below the grinding grain, and also has a small amount of distribution at the grain boundary, but it is relatively weak. The dislocation caused by grinding mainly occurs at grain boundaries. The resulting debris was monolithic, and a few were granular. The interconversion between grains and different structural atoms at the grain boundary is mainly from the crystal lattice atoms in grains to other atoms at the grain boundary. The force is transferred to the grain through the grain boundary, which hinders the transboundary transfer of force and protects the grains. The shearing force plays a dominant role in the grinding process.