Nanoscale investigation of deformation characteristics in a polycrystalline silicon carbide

This paper studied the mechanical behaviour of silicon carbide at the nanoscale, with a focus on the effects of grain orientation and high-dose irradiation. Grain orientation effect was studied through nanoindentation with the aid of scanning electron microscopy (SEM) and (electron backscatter diffraction) EBSD analyses. The grain orientations, expressed in terms of MillerBravais indices, were determined from the Euler angles measured through the EBSD analysis. Mechanical properties such as hardness, elastic modulus and fracture toughness were assessed for different grain orientations. Increased plasticity and fracture toughness were found for indentations made on crystallographic planes which favoured dislocation movement. In addition, for SiC subjected to irradiation, increased hardness and embrittlement were seen from nanoindentations under lower load levels; whereas a decreased hardness and an increased toughness were obtained from nanoindentations at higher load levels. Transmission Electron Microscopy (TEM) analyses revealed that the mechanical response observed atshallow indentation depth was due to the Ga ion implantation, which hardened and embrittled the surface layer of the material as a result of obstruction to dislocations. With increased indentation depth, irradiation-induced amorphization led to a decrease in hardness and an increase in fracture toughness of the material.