Investigation on the effect of cutting edge rounded arc radius on the subsurface damage of FeCoNiCrAl_0.6 high entropy alloy based on molecular dynamics simulation

This investigation delves into the nanomachining mechanisms of the FeCoNiCrAl0.6 high entropy alloy, with an emphasis on the influence of the cutting edge's rounded arc radius. Through molecular dynamics simulations, we explored how variations in the rounded arc radius, cutting depth, and cutting speed impact rheological stress, shear strain, dislocation behavior, and atomic structural transformations. Our findings reveal that grain boundaries serve as a formidable impediment to stress across all machining conditions, initiating significant stress redistribution and concentration within the primary deformation zone. Intriguingly, we uncovered a nonlinear interplay between the shear zone's width and the cutting edge's rounded arc radius at a fixed cutting depth, exhibiting an initial rise, subsequent decline, and a final ascension. The study also established a linear relationship between the sub-surface damage depth and the rounded arc radius for constant cutting speeds. In the quest to optimize the density of 1/6 112 Shockley dislocations, our results indicate that a rounded arc radius under 7.5 angstrom, combined with a cutting speed of 150 m/s, significantly enhances the dislocation density. A similar peak in dislocation density was observed at a rounded arc radius of 15 angstrom, with a 5 angstrom cutting depth and 100 m/s cutting speed. Moreover, surpassing a 10 angstrom rounded arc radius with a 100 m/scutting speed appears to once again elevate the dislocation density. Examining the subtleties of cutting force, we noted a minimum force in the X-direction of roughly 48 nN at a 12.5 angstrom radius and 5 angstrom depth, in contrast to approximately 95 nN at a 5 angstrom radius and 14 angstrom depth. Cutting speeds of 100 m/s with arc radii below 10 angstrom consistently resulted in the lowest X-direction cutting forces, which escalated markedly with larger radii. Temperature dynamics also showed a positive correlation with cutting speed, while the rate of temperature rise demonstrated an inverse relationship. Moreover, despite their scarcity relative to FCC and other atomic configurations, HCP structures were found to critically influence dislocation evolution, especially below a 12.5 angstrom rounded arc radius and at a 14 angstrom cutting depth, where they dominate. Our research provides valuable insights into the adjustment of cutting parameters to mitigate defects and augment the surface integrity of high entropy alloys.