Cavitation damage during high temperature tensile deformation in fine-grained alumina doped with magnesia or zirconia

Abstract

The high temperature tensile ductility of alumina doped with MgO or ZrO{sub 2} is limited around 70--110% for initial grain sizes of about 1 {micro}m. Such limitation may be correlated with strain hardening due to insufficiently suppressed grain growth in MgO-doped alumina or the level of flow stress heightened owing to second phase pinning and/or the intergranular segregation of Zr{sup 4+} ions in ZrO{sub 2}-doped one. This is because higher flow stresses can be assumed to accelerate damage process and thereby to limit tensile ductility. In comparison between these materials, however, such an approach based simply on flow rather similar tensile ductilities as above, irrespective of noticeable differences both in strain hardening behavior and in the level of flow stress between them. Although information on intergranular cavitation damage will give an additional basis for explanation, there has been little quantitative work on cavitation in there martials. The present study, therefore, examined the evolution of cavitation damage in a 0.2-wt%-MgO-doped alumina and a 10-vol%-ZrO{sub 2}-doped alumina with the same initial grain size of 1.0 {micro}m. An emphasis was placed on characterizing the difference in cavitation behavior between the materials.