Combined effects of time and temperature on strength evolution using integral work-of-sintering concepts

Sintered materials have significantly higher strength than green compacts. The evolution of that strength during the sintering cycle involves a combination of annealing, thermal softening, and sintering events. The dynamic interplay between heating rate, sintering time, and sintering temperature controls the in situ strength and determines the final sintered strength. Although sintered strength is a well-explored subject, the dynamic evolution of strength requires new models. This research has measured both the sintered and in situ strengths as functions of heating rate, hold times, and temperature for die-compacted prealloyed bronze powder. A core concept is the use of an integral work of sintering to determine the effective strengthening due to sintering. The model is used to map strength evolution vs the key processing parameters. It is concluded that, during solid-state sintering of bronze, the key sources of distortion are the density and thermal gradients.