High Temperature Deformation Behaviour Of A High Purity Al2O3 Reinforced With Isolated Second Phase Of Spinel (Mgal2O4), Yag (Y3Al5O12) And Zirconia (T-Zro2)

High temperature compression experiments were carried out on high purity aluminia based composites containing second phases of spinel (MgAl2oO4), YAG (yttrium aluminium garnet, Y3Al5O12) and zirconia, (t-ZrO2) at a temperature range of 1623-1723 K, stress range of 10-200 Mpa and a grain size of ~1-10um. It was observed that 5 vol % of these second phases had no significant influence on the creep rate of aluminia. The stress exponent of ~1.0 and the inverse grain size exponent of ~3.0 suggested no change in the creep mechanism of pure aluminia with 5% second phase addition. Deformation enhanced grain growth, which was prominent in pure aluminia, was not observed in the composites. The creep behaviour of the composites was discussed based on ionic radii and ionic charge, room temperature mechanical properties and grain size of individual phases. A new model was developed which took into account the creep rate of the second phase while calculating the creep rate of the composite.