Fracture of Polycrystalline MgAl2O4

Abstract
The fracture toughness of stoichiometric polycrystalline MgAl2O4 was measured as a function of grain size and temperature to 1400°C. The room temperature fracture toughnesses are comparable to reported single‐crystal values. No effect of grain size was detected. Two regions of KIc=f(T) were observed, both showing a decreasing KIc with an increasing T. In the low‐temperature region, fracture is of a mixed mode, transgranular and intergranular character. The ∼10−4 MN/m3/2°C (dK10dT) decrease is governed primarily by dE/dT. The high‐temperature region, T >900°C, has a much larger dK10dT decrease, ∼ 10−3 MN/m3/2°C, and a fracture character that is totally intergranular, suggesting dominance by grain‐boundary processes.

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