A critical stress–critical area statistical model of the curve for MA957 in the cleavage transition

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