Surface modification mechanism of laser-assisted grinding process for high silicon aluminum alloy: A molecular dynamics study

High silicon aluminum alloy has attracted wide attention due to its excellent performance. However, the processing difficulty greatly limits the application scope of the material. In this paper, the surface modification mechanism of high silicon aluminum alloy at different laser energy densities was investigated by molecular dynamics simulations. The results show that the increase of the laser energy density leads to the weakening of the interatomic bonding force of the material, which results in a significant reduction of the grinding force. Compared to conventional grinding, the average tangential and normal forces decreased by 57.9 % and 86.6 % when the laser energy density is 200 eV/ps. The depth of the high shear strain region varies nonlinearly with the increase of laser energy density, which indicates the dynamic competition between mechanical stresses and thermal effects in the machining process. With the increase of laser energy density, the transformation rate of Al matrix to amorphous and hexagonal close-packed structures accelerated, the number of transformed atoms increased, and the hindering effect of Si particles on the abrasive was also weakened. Compared with conventional grinding, the dislocations, stacking faults, and twin boundary density are significantly reduced in laser- assisted grinding. This is mainly attributed to the laser thermal effect, which promotes the dynamic recrystallization, defect annihilation, and atomic rearrangement processes. Additionally, the laser heating effect enhances the interaction between dislocations, crystal planar defects, and Si particles, promoting dynamic recrystallization and the annihilation of defects. This paper provides a comprehensive understanding of the defect evolution mechanisms during laser-assisted grinding and establishes a theoretical basis for optimizing machining parameters.