A MATHEMATICAL-MODEL FOR GRAVITY-INDUCED DISTORTION DURING LIQUID-PHASE SINTERING

Liquid-phase-sintered materials consist of interconnected crystalline grains in a homogeneous matrix phase that forms a liquid during sinter ing. These composites exhibit viscous flow during sintering that allow s densification. Gravitational forces give rise to compact distortion when there is a large amount of liquid at a high temperature. This art icle treats kinetic aspects of distortion during sintering of tungsten heavy alloys (W-Ni-Fe). The mathematical model predicts distortion an d highlights the important variables influencing this phenomenon. The results provide guidelines for minimizing distortion due to gravity. E xperiments conducted at several different sintering times show reasona bly good agreement with theoretical predictions using the liquid-phase viscosity as a single adjustable parameter. Theoretical predictions o f the model are crucial to designing microgravity experiments aimed at understanding dimensional stability.