End‐Point Density of Hot‐Pressed Alumina

Hot‐pressed aluminum oxide has been found to exhibit an asymptotic end‐point density. The temperature and pressure dependence of this end‐point density has been investigated over the range of temperature from 1100° to 1500°C and pressure from 500 to 6000 psi. The pressure dependence of the end‐point density can be explained in terms of a plastic‐flow model which exhibits a critical shear stress. The temperature dependence suggests that this critical shear stress is a thermally activated process with an activation energy of 39 kcal per mole.