Atomistic Studies of Crack Growth Mechanisms in Silicon Carbide
Kelvin Leung (Cornell Univeristy), Zhi liang Pan (), Derek Warner (Cornell University)
Materials for Extreme Environments: Multiscale Experiments and Simulations
Mon 2:40 - 4:00
Salomon 203
The promise of Silicon Carbide (SiC) as high temperature structural material has long been limited by its low fracture toughness. While SiC components have developed higher fracture toughness by advanced manufacturing processes and optimization of microstructures, further improvement is still needed. This motivates our group’s current effort to better illuminate the controlling fracture mechanisms in SiC. Using a collection of atomistic based approaches, we found that crack growth mechanisms depend highly on temperature and loading rate. Molecular dynamics (MD) simulations with empirical potentials and analytic modeling based on the Peierls concept both suggest the possibility of two transitions in crack tip behavior with increasing temperature. At the lowest temperatures, the crack tip cleaves in a purely brittle manner. At moderate temperatures the crack tip nucleates dislocations on {111} planes, while at higher temperatures dislocations are nucleated on {100} planes. After confirming the analytic model’s ability to reproduce direct MD simulation results, we compare the MD and analytic predictions for fracture mechanisms with coupled quantum (Kohn-Sham density functional theory) and continuum simulations.