Primary Recrystallization During the Hot‐Pressing of MgAl2O4

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Abstract
Magnesium aluminate powders, both pure and doped with 0.5 wt% LiF, were hot‐pressed under vacuum at 1050°, 1170°, and 1290°C and 2500 and 5000 psi. Densification data were analyzed according to the classical hot‐pressing equation, In P/P0= ‐Kt; deviations are discussed in terms of the Occurrence of primary recrystallization. Examination of fracture surfaces and thermally etched polished surfaces by SEM corroborated this approach, indicating that strain‐induced primary recrystallization Occurred during hot‐pressing. Increased hydrostatic components of stress resulting from the presence of a liquid phase associated with LiF are proposed as the cause of plastic flow in the LiF‐doped spinel at low temperatures. Analogies are suggested between densification during primary recrystallization and reactive hot‐pressing.