Molecular dynamics simulation for temperature assisted machining of a polycrystalline γ-TiAl alloy

Abstract

Temperature-assisted machining is an effective method for improving the machining quality of difficult-to-machine materials. A nano-cutting model was developed using molecular dynamics simulation to reveal the effect of temperature on the cutting performance of a polycrystalline γ-TiAl alloy. The effects of temperature on cutting force, tool wear, plastic deformation, microstructure evolution, subsurface damage, and surface formation process were analyzed based on the levels of thermal activation energy and dislocation theory. Results indicated that the machining quality was a combination of the softening of temperature fields and hardening of stress fields. If the assisting temperature was too high or low, the temperature fields and the stress fields, one of which dominates, the improvement in machining quality was poor. When the assisting temperature was approximately 500 K, the temperature fields and the stress fields matched, plastic deformation, tool wear, and subsurface damage were small, and the machined surface quality was relatively optimal. Recovery and recrystallization lead to microstructural evolution; higher temperatures increased the degree of migration of grain boundaries, and the removal of material from the shear mode gradually transitioned to the removal mode for the coexistence of shear and extrusion. This study can deepen our understanding of the temperature-assisted machining characteristics of the alloy and provide a theoretical basis for regulating the performance of the alloy and improving the machining quality at a macro scale.