Effects of temperature and grain size on the mechanical properties of polycrystalline quartz

In this article, a series of molecular dynamics (MD) simulations were performed to investigate the impacts of indentation size, grain size and temperature on the mechanical properties of polycrystalline alpha-quartz under quasi-static nanoindentation with conical indenter. Results from MD simulations show that the hardness and Young's modulus are more sensitive to the temperature and penetration depth than grain size. Von Mises shear strain and the volumetric strain were calculated to depict the plastic deformation and it was found that plastic deformation becomes more dominate at higher temperatures and indentation sizes for polycrystalline alpha-quartz. The deformation mechanism is dominated by the grain boundary sliding instead of intragranular dislocation control at small grain size (<10 nm). This work enriches the atomic-level understanding the mechanical properties of alpha-quartz under nanoindentation tests, which helps to uncover the mechanism of polycrystalline solids breakage and deformation under various conditions.