Molecular dynamics study in mechanical behavior of reaction-bonded silicon carbide under uniaxial loading and nanoindentation

Reaction-bonded silicon carbide (RB-SiC) is an important candidate material in advanced optical systems owing to its excellent properties. Due to the coupling between Si and SiC phases as well as the existence of phase/grain boundaries, the material deformation mechanism becomes complex. Molecular dynamics models for uniaxial loading as well as nanoindentation of RB-SiC are established to study the atomic-scale deformation mechanism of the material. Simulations with Si proportions in RB-SiC in the range of 9.6%—48.8% and equilibrium temperatures ranging from 300 to 900 K are conducted to study the effects of temperature and Si proportion. The basic uniaxial tension and compression as well as nanoindentation processes are analyzed based on the stress-strain curves and load-depth curves. The different fracture mechanical behaviors in tension and compression are discussed in detail. The deformation and phase transformation behaviors in nanoindentation are analyzed. Simulation results show that elevated temperatures decrease the Young's modulus, hardness and strength of RB-SiC by enhancing the fluidity of the amorphous atoms near the boundaries and promoting the grain sliding. Proportion of Si can significantly influence the material physical properties because of the intrinsic property differences of Si and SiC inside the material. Higher Si proportion decreases the Young's modulus and hardness calculated by nanoindentation and the tensile/compressive Young's modulus and strength obtained from the uniaxial loading conditions. Our results will be helpful for machining of RB-SiC and the practical applications of this material.