Superplasticity in alumina enhanced by co-dispersion of 10% zirconia and 10% spinel particles

Superplastic deformation behavior is examined for Al2O3-based ceramics disp ersed with 10 vol% ZrO2 and 10 vol% spinel (MgO 1.3 Al2O3) particles. The m ultiple-phase dispersion considerably decreases the rate of grain growth du ring deformation, leading to enhanced superplasticity (larger tensile elong ation and higher strain rate). Maximum tensile elongation reaches 850% at a strain rate of 5.0 x 10(-4) s(-1) and at 1500 degreesC, Grain growth durin g deformation is Found to follow a theoretical model based on a grain bound ary diffusion mechanism. The creep parameters corrected for concurrent grai n growth are 2.2 as the stress exponent, 3.2 as the grain size exponent and 751 kJ/mol as the activation energy. Spherical ZrO2 particles embedded in elongated Al2O3 grains in deformed specimens suggest that the deformation m echanism of the present material is strongly related to grain boundary diff usion. Being different from other superplastic aluminas, cavities in the pr esent material tended to grow in the direction parallel to the stress axis. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All right s reserved.