Polycrystals of hot-isostatically pressed MgO·Al_2O_3 spinel, having a fine-grained size of 610 nm, have been deformed in uniaxial compression. The results have been analysed by taking into account grain growth. The variation in stress exponent n suggests a transition from interface reaction (n = 2) at low stresses to diffusional mechanism (n = 1) at high stresses, but cavitational creep was responsible for the non-linear behaviour at stresses above 60 MPa. The grain size exponent found at 60 MPa (p = 3), the absence of dislocations within the fine grains and the similarity of equiaxed grain shapes before and after large flow (≈40/100) resemble the charac- teristics of micrograin superplastic flow.
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