A multiscale simulation investigation on subsurface dislocation motion evolution mechanism in ultra-precision machining process

During practical ultra-precision cutting, the titanium alloy specimens suffer a combination of various deformations, has great influence on machining precision and properties. Here we report, the microstructure changes and surface mechanical properties evolutions were studied using two-dimensional climb assisted discrete dislocation dynamic technology. The plastic deformation is modeled through the motion of edge dislocations in an elastic matrix with dislocation nucleation, lock, interaction with obstacle
and grain boundary, annihilation incorporated a series of constitutive equations. It was found that the micro-structure was obviously refined due to the variation of cutting force, which can be described as following: the formation and development of dislocation lines in initial grain, the formation of dense dislocation walls, the transformation of dislocation lines and walls into
subgrain boundaries. In addition, the variation of surface microstructure results in higher flow strength and hardening rate due to the accumulation of geometrically necessary dislocations. The numerical result is helpful to reveal the effects of these microstructural factors on the surface generation mechanism in ultra-precision machining.