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 inte raction between gravitational forces and capillary forces. We provide an an alysis of this mechanism for gradient formation and show that for most impo rtant engineering materials, solution-reprecipitation does not cause substa ntial gravity-induced gradients. This conclusion is in agreement with publi shed data for tungsten heavy alloy materials containing volume fractions of solids greater than about 0.7 at the sintering temperature. Macrostructura l gradients in liquid phase sintered materials have been reported in the li terature; however, these materials contain sufficient liquid at the sinteri ng temperature that solid grains settle within the liquid, perhaps contribu ting to the observed gradients.