The effect of contiguity on growth kinetics in liquid-phase sintering

Experimental and mathematical consideration of microstructural coarsening during liquid-phase sintering has resulted in kinetic laws which define grain size to the third power as being proportional to the isothermal sintering time. Despite thoseprior efforts, the situations typical to liquid-phase sintering are poorly treated by the current models because the models assume a structure consisting of widely separated spherical grains (zero contiguity). No experiment had been completed to quantify the effect of contiguity on the growth kinetics. In order to do this, the contiguity and growth rates of tungsten grains in a liquid matrix at 1,750K were measured in sintered heavy alloys of 78,83, 88,93 and 98 wt.% Wbalanced with 70Ni-30Fe. The observed grain growth rates were compared with the theoretical predictions of the LSW theory and volume fraction modified theories. By modifying the volume fraction effect with a contiguity term, a model was produced that closely followed the experimental results.