EXPERIMENTAL INVESTIGATION OF PARTICLE-SIZE DISTRIBUTION INFLUENCE ONDIFFUSION-CONTROLLED COARSENING

The influence of initial particle size distribution on coarsening duri ng liquid phase sintering has been experimentally investigated using W -14Ni-6Fe alloy as a model system. It was found that initially wider s ize distribution particles coarsened more rapidly than those of an ini tially narrow distribution. The well known linear relationship between the cube of the average particle radius, r3BAR, and time was observed for most of the coarsening process, although the early stage coarseni ng rate constant changed with time, as expected with concomitant early changes in the tungsten particle size distribution. The instantaneous transient rate constant was shown to be related to the geometric stan dard deviation, lnsigma, of the instantaneous size distributions, with higher rate constants corresponding to larger lnsigma values. The for m of the particle size distributions changed rapidly during early coar sening and reached a quasi-stable state, different from the theoretica l asymptotic distribution, after some time. A linear relationship was found between the experimentally observed instantaneous rate constant and that computed from an earlier model incorporating the effect of pa rticle size distribution. The above results compare favorably with tho se from prior theoretical modeling and computer simulation studies of the effect of particle size distribution on coarsening, based on the D eHoff communicating neighbor model.