The effect of gravity on solution-reprecipitation during liquid phase sintering

Solution-reprecipitation during liquid phase sintering can lead to gravity-aligned gradients in the amount of refractory phase as a result of the interaction between gravitational forces and capillary forces. We provide an analysis of this mechanism for gradient formation and show that for most important engineering materials, solution-reprecipitation does not cause substantial gravity-induced gradients. This conclusion is in agreement with published data for tungsten heavy alloy materials containing volume fractions of solids greater than about 0.7 at the sintering temperature. Macrostructural gradients in liquid phase sintered materials have been reported in the literature; however, these materials contain sufficient liquid at the sintering temperature that solid grains settle within the liquid, perhaps contributing to the observed gradients.