Evaluation of dimensional changes from as received dilatometric sintering plot

Abstract

During the dilatometric study, powder compact initially shows the expansion before the onset of sintering. This expansion was found to be influenced strongly by the factors such as gases, stresses, phase change, etc. The present work demonstrates a systematic method to eliminate the influence of these factors from the dilatometric plot and to estimate true shrinkage, in different metal powders [microsize Ni, Fe, Ti, Ti–2Al (at.-%) and nanosize Ti and Ni]. First, the coefficient of thermal expansion α_c of the sintered sample from the cooling curve was estimated and the expansion of green compact from room temperature to final temperature was calculated based on α_c, assuming that there was no shrinkage during heating. Finally, from this expansion, the shrinkage was measured. The necessary corrections were incorporated where the volumetric changes occurred owing to phase transformations.