Densification and Grain Growth in the Later Stages of Sintering of Alpha-Iron

Abstract

Only few studies have been made of the mechanism of sintering of body-centered cubic metals. On the author’s part, interest in the sintering of α-iron is enhanced by the observation [1, 2] of a dominant contribution of surface diffusion during the initial stage of sintering of wire spool models in the α range. Together with the empirical fact that fine iron powders do exhibit considerable shrinkage on sintering in the alpha range (which is incompatible with a surface diffusion mechanism) these wire spool experiments indicated that the mechanism of material transport might depend on the particle size of the sintering system. This stimulated a systematic study of particle size dependence which is still in progress. As a first step it was decided to study the sintering of carbonyl iron powder. This powder can be sintered to nearly full theoretical density below the transformation temperature, which makes it very suitable for a study of shrinkage mechanism.