Microstructure and mechanical properties of hot pressed Al₂O₃–ZrO₂ceramics prepared from ultrafine powders

Abstract

The microstructure and mechanical properties of hot pressed Al2O3–ZrO2 ceramics prepared from ultrafine powders were studied by means of hardness and fracture toughness tests, X-ray diffraction, scanning and transmission electron microscopy, and electron probe microanalysis. Experimental results show that Al2O3–ZrO2 ceramics combine the high modulus of Al2O3 and phase transformation toughening of ZrO2 and give good mechanical properties. The fracture toughness of the samples increases monotonically with increasing ZrO2 content. When the content of ZrO2 is low, the ZrO2 particles are surrounded by Al2O3 grains and the matrix is thus strengthened, but when the content of ZrO2 is high, the microcracks resulting from the tetragonal monoclinic phase transformation decrease the strength of the material. The relative density of the samples also increases with increasing ZrO2 content, which is beneficial to both strength and toughness. Banded abnormal growth of the Al2O3 grains parallel to the hot pressing plane was found in the samples. This phenomenon is considered to be a result of the priority of Al2O3 grain growth and aggregation of ZrO2 along the pressing direction in the later stages of hot pressing.MST/1359