Densification behavior of a fine-grained MgAl2O4 spinel during spark plasma sintering (SPS)

The densification rate of a spinel during spark plasma sintering can be characterized by the decreasing stress exponent from ⩾4 to ≈1 as the density increases. Transmission electron microscopy observations showed that stacking faults introduced by partial dislocations are observed in a low-density region, but limited in a high-density region. These results suggest that the dominant densification mechanism changes with density, from plastic flow caused by a partial dislocation motion to diffusion creep as the density increases.