Kinetics of Hot‐Pressing: The Semilogarithmic Law

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Abstract
A proportionality has often been observed between the density of a sample during sintering and hot‐pressing and the logarithm of the sintering time; this has usually been explained as the consequence of grain growth occurring during the densification. An alternative explanation is given for the case of hot‐pressing under conditions where densification is brought about by plastic flow (dislocation creep); this explanation is based on a stress multiplication factor which is exponentially dependent on the porosity. The exponential form of stress concentration factor can originate where rapid mass transport near the pores allows the development of an equilibrium micro‐structural configuration. Important consequences of this model result for the interpretation of hot‐pressing kinetics; experimental support for the model has been found in the hot‐pressing of high‐purity magnesium oxide.