GRAVITATIONAL EFFECTS ON GRAIN COARSENING DURING LIQUID-PHASE SINTERING

Grain growth in liquid-phase sintering (LPS) is often treated as an ex tension of Ostwald ripening. However, the inherent grain contact at hi gh solid contents leads to coalescence and other conflicts with most c oarsening theories. Consequently, grain growth rates during LPS signif icantly deviate from the predictions of most coarsening theories. This study compares grain sizes of tungsten heavy alloys sintered on Earth and under microgravity conditions. The microgravity samples consisten tly produced a smaller grain size. A case is made for a gravity contri bution to coarsening during LPS. Such a concept provides a rationaliza tion for previously reported differences in sintered grain size with l ocation in compacts sintered on Earth.