PARTICLE FRAGMENTATION DURING SUPERSOLIDUS SINTERING

Supersolidus sintering involves densification by liquid formation in a prealloyed powder by heating above the solidus temperature. The criti cal stage during densification is associated with the formation of a t hreshold amount of liquid along the grain boundaries of a polycrystall ine particle, leading to fragmentation and densification by a viscous flow process. This paper covers model experiments involving the coales cence of floating oil droplets dispersed with polymer grains that simu late various solid-liquid ratios. Such experiments show that grain sli ding occurs during fragmentation due to the presence of a shear stress adjacent to the neck region. The threshold liquid content is determin ed experimentally using a Ni-base alloy and stainless steel and these results conform to earlier model predictions.