Mechanical Properties of Fine‐Grained Magnesium Oxide at Large Compressive Strains

Fine‐grained polycrystalline MgO specimens were deformed in compression at constant strain rates of ∼6.7×10 −6 s −1 to 6.7×10 −5 s −1 at 1173 to 1423 K. Both mechanical data and microstructural observations are distinctive of a diffusion‐accommodated flow, where the grain‐size parameter is of prime importance in enhancing plasticity. Under suitable experimental conditions, superplastic strain was achieved in specimens; no change was detected in the equiaxed‐grain shape configuration. Finally, the effect of grain growth during deformation was considered; specimens of initial grain size ∼0.1 μm showed an apparent hardening which was quasi‐linear with time.