Influence of nano-indentation depth on the elastic–plastic transformation of 6H-SiC simulated

Abstract

To investigate the effect of nano-indentation depth on the elastic–plastic transition mechanism of 6H-SiC, the loading process of nano-indentation on a 6H-SiC⟨0001⟩ crystal surface is analyzed by using the molecular dynamics method. Diamond indenters and 6H-SiC amorphous nanolayers are constructed; Tersoff and Vashishta potential functions are established to describe the interactions between atoms; and simulated environmental factors, such as relaxation conditions, ensemble, and loading speed, are optimized. The stress distribution and internal deformation characteristics are analyzed by combining load–displacement curves, radial distribution curves, dislocation nucleation, and their evolutive processes. The load–displacement curve deviates from the theoretical value at a depth of 3.8 nm and enters the elastic to plastic transition phase, where the shear stresses generated by friction on the contact surfaces cause the atoms on the stacked layers in the elastic phase to move in a directional manner and form dislocations: edge-type dislocations connecting the two layer dislocations and horizontal spiral dislocations. The plastic deformation phase starts at a depth of 5.9 nm, the atoms keep migrating and reorganizing, the original dislocation rings break to form incomplete dislocations, and the new dislocations formed by the combination of partial edge-type dislocation rings expand internally until fracture. The formation and expansion of dislocations contribute to the elasto-plastic transformation of 6H-SiC, and amorphous states are found to be involved in the deformation process at both the indentation contact surface and the deformation layer. Moreover, there are differences in the direction of dislocation expansion due to the inhomogeneous stress distribution at the contact surface.