The influence of a magnetic field on the fracture toughness of ferromagnetic steel

The limited data available suggest that the mechanical properties of ferrom agnetic alloys are not significantly affected by high magnetic fields. As f urther evidence, the present paper includes data on the fracture toughness of Incoloy 908, a ferromagnetic austenite, in fields up to 14T at 4.2 K. Th e field has no significant effect on the toughness. To interpret these resu lts we review the available theoretical work on the fracture of ferromagnet ic materials in magnetic fields. The model of Shindo is particularly releva nt, and suggests that there is no measurable effect on the toughness of fer romagnetic steel at fields below about 25 T and no significant effect until the field exceeds 75 T. Interestingly, the theory does suggest a possible increase in the toughness of steels with very high magnetic permeability at fields below saturation.