Presintering effects on ground-based and microgravity liquid phase sintering

Tungsten heavy alloys are an ideal system for liquid phase sintering studies. The sintering behavior and postsintering microstructure depend to a large degree on the processing conditions. While grain growth, final microstructures, and mechanical properties are fairly well understood, the role of presintering conditions is poorly documented. This article discusses presintering condition effects on the subsequent liquid phase sintering densification and distortion during both ground-based and microgravity sintering. It provides unique insight into the events accompanying densification and shape distortion, such as solid-liquid segregation and pore stability. Solid-liquid segregation is closely connected to densification. Presintering conditions play an important role in the mobility and the location of the pores in the sample, which can be explained in terms of the interfacial energy between different phases. In ground-based sintering, the cold-isostatically pressed sample has the most uniform solid-liquid distribution with the largest shrinkage. In microgravity sintering, the vacuum-presintered sample shows the largest degree of densification and elimination of pores.