A critical stress-critical area statistical model of the KJc(T) curve for MA957 in the cleavage transition

We model the temperature (T) dependent fracture toughness KJc(T) of MA957 based on a statistically modified critical stress-critical stressed area (σ*-A*) local fracture criteria. The KJc(T) of MA957 is strongly dependent on the specimen orientation. Analysis of cleavage initiation in the longitudinal-radial (L-R) orientation, with the highest KJc(T), yielded the highest σ*∼3600MPa. In contrast, the σ* for the circumferential-longitudinal (C-L) orientation, with the lowest KJc(T), yielded the lowest σ*∼2850MPa, while for the circumferential-radial (C-R) orientation with intermediate KJc(T), σ*∼3000MPa. The A* ranged from ∼ 30 to 400μm2. The cleavage initiation sites are μm-scale Al2O3 particles aligned in the textured low toughness extrusion direction