Role of polymorphic transformation in the hot pressing of alumina

Conclusions At temperatures of up to 1400°C hot pressing under isothermal conditions enables higher (by 5%) densities to be obtained in compacts from-Al₂O₃ powders than in compacts from-Al₂O₃ powders. With rise in temperature the difference between the densification rates of- and -Al₂O₃ powders diminshes. The difference in density between- and-Al₂O₃ compacts is preserved up to a temperature of 1600°C in hot pressing at a constant heating rate of 5 deg C/min. In the temperature range 1300–18QO°C the energy of activation for hot pressing Al₂O₃ varies from 50 to 75 kcal/g· form. Estimated values of viscosity and effective diffusion coefficient are in accord with values determined in creep and sintering experiments.Translated from Poroshkovaya Metallurgiya, No. 9(165), pp. 76–80, September, 1976.