Processing‐Related Fracture Origins: II, Agglomerate Motion and Cracklike Internal Surfaces Caused by Differential Sintering

Effects of differential sintering kinetics due to differential green density were studied by fabricating agglomerate‐powder matrix specimens from two Al 2 O 3 /ZrO 2 (30 vol%) powders and subjecting them to a cyclic sintering schedule to allow intermittent observations. Low‐green‐density compacts sintered faster than high‐density compacts, although high‐green‐density compacts reached end‐point densities first. Specimens containing low‐green‐density agglomerates produced circumferential cracklike voids at the agglomerate/matrix interface. Agglomerates with a higher green density than the matrix were subjected to compressive strains by the matrix to produce agglomerate motion when the resulting stress field was non‐symmetric. Such agglomerates also produced a variety of cracklike separations. Implications regarding sintering kinetics and end‐point densities are discussed. Implications regarding strength of sintered bodies are obvious, viz. strength can be proportional to the square root of the agglomerate size.