Effect of MgAl2O4 spinel dispersion on high-strain-rate superplasticity in tetragonal ZrO2 polycrystal

Abstract

The effect of second phase dispersion on high-strain-rate superplasticity was examined in tetragonal ZrO2 dispersed with 30vol% MgAl 2O4 spinel. The spinel particle enhances the diffusivity of ZrO2 by supplying small amounts of aluminum and magnesium into ZrO2 and suppresses grain growth by grain boundary pinning. After superplastic flow, the spinel particles highly elongate along the tensile direction. In the spinel particles, intragranular dislocations were observed, indicating that the spinel particles may contribute to the relaxation of stress concentrations around grain junctions exerted by grain boundary sliding. Comparison with earlier studies suggests that the dispersion of spinel particles can attain high-strain-rate superplasticity in tetragonal ZrO 2 through providing the following positive factors simultaneously; (i) the suppressed grain growth, enhanced accommodation process due to the accelerated (ii) diffusivity and (iii) stress relaxation.