Effect of Grain Size on Mechanical Properties of High-Purity Polycrystalline Magnesia

Abstract

High-purity polycrystalline magnesia with different microstructures were prepared, and the effects of grain size on their bending strength and thermal shock damage resistance were investigated. The bending strength (δB) increased with decreasing grain size (D: μm), and expressed by following equationn. δB=403D-0.26 (MPa). On the other hand, the thermal shock damage resistance increased linearly with increasing grain size, which was explained by the damage resistance parameter, R′′′=E/σT2(1-ν), where E is Young's modulus, ν is Poisson's ratio and σT is tensile strength. E and ν are unchanged and σT(σB×0.6) decreased with increasing grain size, so R′′′ increased with increasing grain size. Consequently, thermal shock damage resistance increased with increasing grain size.