On crack-propagation-related phenomena in Al₂O₃ + ZrO₂ and Al₂O₃ sintered in air and hydrogen

Abstract

Experiments on Al₂ + ZrO₂ ceramics reveal higher Young′s moduli and fracture toughness after sintering in air then in hydrogen. Since X-ray measurements showed a higher monoclinic phase content in the air-sintered material, Young′s moduli of these ceramics indicate the existence of higher residual stresses associated with a lower degree of spontaneous transformation-induced microcracking. This effect corresponds to a lower microcrack density observed on fracture surfaces of air-sintered single-phase alumina compared with the same Al₂O₃ sintered in H₂. These results are in agreement with the estimated grain boundary strengths of the examined ceramic materials.