Nanoscale understanding of the tribological removal behaviors for additive-fabricated Ti6Al4V alloy under the magnetorheological polishing

Abstract

In order to enhance the surface quality of Ti6Al4V workpieces and overcome the problems of work-hardening and ablation phenomena that exist in conventional machining, magnetorheological polishing method is introduced to improve the surface quality of additively molded Ti6Al4V. In this study, the tribological removal behavior of additively fabricated Ti6Al4V alloys at the nanoscale is systematically revealed through molecular dynamics (MD) simulations combined with magnetorheological polishing (MRP) experiments and nano-scratch tests. A joint EAM-Tersoff-Morse potential function model was used to simulate the interfacial interaction between SiC abrasive particles and Ti6Al4V workpieces, and to analyze the effects of sliding parameters on the temperature field, force field, and subsurface damage. The experimental results show that the surface roughness decreases and then increases with increasing pressure, the material removal rate continues to increase with increasing pressure, and the residual stress decreases by 76.75 %.The MD simulation shows that the increase of the abrasive grain sliding depth leads to the increase of the surface atomic displacement, the thickening of the subsurface damage layer, and the decrease of the dislocation density with the increase of the sliding speed. The nano-scratch experiments verified the law of friction increasing with pressure in the simulation, and revealed that the friction coefficient varied nonlinearly at high speeds due to thermal effects. The simulations and experiments are highly consistent with each other in terms of surface roughness, material removal rate and residual stress trends. This study provides a theoretical basis for optimizing the MRP process parameters, which is of great significance in guiding the surface treatment of aerospace precision components and medical implants.