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 jc (T) of MA957 based on a statistically modified critical stress-critical stressed area (σ*-A*) local fracture criteria. The K jc (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 jc (T), yielded the highest σ* ≈ 3600 MPa. In contrast, the σ* for the circumferential-longitudinal (C-L) orientation, with the lowest K jc (T), yielded the lowest σ* ≈2850MPa, while for the circumferential-radial (C-R) orientation with intermediate K jc (T), σ* ≈ 3000 MPa. The A* ranged from ≈ 30 to 400 μm 2 . The cleavage initiation sites are μm-scale Al 2 O 3 particles aligned in the textured low toughness extrusion direction.