Understanding the changes in mechanical properties due to the crystalline-to-amorphization transition in SiC

Atomic-scale simulations of tensile testing are performed on a series of silicon carbide (SiC) with varying chemical disorder to investigate the changes in mechanical properties due to the accumulation of irradiation damage. The accumulation of chemical disorder, which drives the crystalline-to-amorphization (c-a) transition, plays a significant role on the variations of Young's modulus and strength, but in different manners. Young's modulus decreases almost linearly with increasing chemical disorder below some threshold (X= N _C-C / N_C-Si <∼0.54). However, strength exhibits abrupt substantial reduction with the presence of a slight chemical disorder (=0.045). Above the threshold, the degradations of Young's modulus and strength tend to saturate, indicating the completion of c-a transition. The variations of the mechanical properties as a function of chemical disorder are closely correlated with the crossover from homogenous elastic deformation to localized plastic flow percolating through the system. The crossover arises from the interplay between uncorrelated atomic slipping confined within topological disordered clusters and the constraint from topological ordered ligaments. The crossover is also manifested in fracture mechanisms switching from lattice instability to some type of ?ductile? fracture preceded by nanocavity percolation.