Effect of Grain Size on Transverse Bend Strength of Alumina and Magnesia

Experimental findings are presented for the effect of microstructure on the room-temperature transverse bend strength properties of hot-pressed dense pure alumina and magnesia. Bend strength shows an exponential dependence on porosity but is sensitive to fabricating temperatures because of changes in grain size. Log-log plots of strength (extrapolated to zero porosity) versus grain size reveal the relation
S = 86,000 G ^−1/3 (psi) for alumina and S = 50,000G^−1/6 (psi) for heat-treated specimens of magnesia ( G = grain size in microns).