Effects of Composition and Grain Size on Surface Damage and Deformation Mechanism of Nicocrfe High Entropy Alloys

The effect of composition, grain sizes (GSs), and cutting depths on the mechanical properties, deformation behaviors, and subsurface damages of nanoschratched NiCoCrFe high entropy alloys are investigated using molecular dynamics (MD) simulation. The ability to remove atoms during the cutting process depends on the alloy composition and GSs. When Ni, Co compositions are kept constant, the cutting force and the average friction coefficient reduce, while the total dislocation length rises as rising Cr composition and reducing Fe composition. When Cr, Fe compositions are kept constant, the friction coefficient and total dislocation length increase as decreasing Ni composition and increasing Co composition. The temperature of the Ni 25 Co 25 Cr 25 Fe 25 specimen is significantly larger than other specimens, which weakens the bonds of atoms over a large area leading to an increase in the number of worn atoms. The deformation mechanism presents that GBs keep a vital act in barring the propagation dislocation and the development of stacking fault. The GBs also act as an intermediary path to release thermal residual stresses to help reduce cutting force. Interestingly, the number of worn atoms clearly increases as increasing average GS to 7.2 nm, then decreases as continuously increasing GS to 8.7 nm