Mechanical Properties of Pure, Dense Magnesium Oxide as a Function of Temperature and Grain Size

The elastic modulus and transverse bend strength of pure, dense magnesia were determined as a function of grain size (1 to 190μ) and temperature (30° to 1500°C). The elastic modulus was essentially independent of grain size over the temperature range covered. The transverse bend strength for magnesia revealed a 1/6 power dependency versus grain size at low temperatures, i.e. S TB = 50,000 G −1/6 At temperatures above approximately 600°C, the strength of specimens of all grain sizes tested decreased with temperature and the grain size dependence, of strength also decreased. Nonlinear load‐deflection behavior was observed at temperatures above approximately 700°C and etch pit observations of dislocations produced during deformation and fracture of large‐grain magnesia specimens revealed extensive slip in grains adjacent to the fracture area.