Abstract
It has been established that the fall in the activity of a tungsten powder produced by reduction at 950°C and annealed, before pressing, at a temperature of 1700°C or higher is due not to growth of its particles during the annealing but to a decrease in the internal porosity of the particles and their agglomeration and spheroidization. With single-fraction as-reduced and annealed powders their is a correlation between the maximum size of pore channel constructions in a compact and the letter's sintering behavior. Prior heat treatment of tungsten powders produced by reduction at an end temperature of 700°C exerts a nonmonotonic influence on their sintering activity. Shorttime (τ=30 sec) sintering of compacts from such tungsten powders has been found to result in the formation of a new porous structure, with enlarged maximum pore channel constrictions, responsible for their sintering behavior. A correlation has been discovered between the volume shrinkage of compacts and the maximum size of constrictions in the enlarged capillaries.
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