Atomic-scale investigation of Pt composition on deformation mechanism of AuPt alloy during nano-scratching process

In this research, we performed molecular dynamics (MD) simulation to investigate the material removal mechanism and subsurface damage formation during nano-scratching of the gold-platinum (AuPt) alloy. In order to comprehend the deformation mechanism of AuPt alloy during nano-scratching, the influences of Pt composition in workpiece on the machining performance were analyzed. The results indicate that the Pt composition has a significant influence on the surface morphology including piling-up of workpiece atoms and elastic recovery on the machined surface. During the deformation process, the average shear strain of workpiece atoms decreases when the Pt composition increases. Besides, the average scratching force increases apparently with obvious fluctuation as the Pt composition increases. For the subsurface damage formation, typical crystal defects including atomic clusters, V-shape stacking fault couples, and stacking faults tetrahedra were observed in the workpiece subsurface. The lengths of perfect dislocations and Shockley partial dislocations gradually increase as Pt composition increases, while the overall length of sessile dislocations decreases obviously. Meanwhile, thinner stacking faults were formed in the workpiece subsurface as the balanced width of stacking fault gradually decreases when the Pt composition increases. This work contributes to a better understanding of the nanoscale deformation mechanism of bimetallic materials during micro or nano machining process.