Effect of gravity on three-dimensional coordination number distribution inliquid phase sintered microstructures

Gravity affects microstructural evolution when a liquid phase is present du ring sintering. The effect of gravity on the three-dimensional coordination number distribution of tungsten grains in liquid phase sintered heavy allo y specimens is quantitatively characterized. A combination of montage seria l sectioning, digital image processing, and unbiased stereological sampling procedures is used to estimate the coordination number distribution in thr ee-dimensional microstructures. The microgravity environment decreases the mean coordination number. However, hardly any isolated grains are observed in the specimens, liquid phase sintered in a microgravity environment. The effect of microgravity on the coordination numbers mainly resides in its ef fect on the mean coordination number. In all specimens, there is a strong c orrelation between grain size and coordination number, which can be express ed as [D-c/(D) over bar](2) = C/C-0 where C-0 is the mean coordination number, (D) over bar the global average size of the tungsten grains, and D-c the average size of only those grains which have coordination number C. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.