Deformation and fatigue crack growth of iron(81) boron(13.5) silicon(3.5) carbon(2) amorphous metal using magnetostrictive behavior to generate delta K

The deformation and fatigue crack growth behavior of amorphous metals are presented. A discussion of magnetic domains, and their influence on magnetostriction is also included. Testing of Metglas 2605SC, utilizing magnetostriction to generate DeltaK, indicated near-threshold (Region I) fatigue crack growth behavior for as-cast and annealed specimens. A Delta Kth on the order of 0.6-1.0 kg/mm^3/2 was also indicated. The best crack growth rate behavior was obtained for transverse field-annealed specimens. Significant variability in the data, however, prevented a determination of Delta Kth for this condition. A life prediction model based on a Paris equation was developed. Crack growth data were consistently lower than predicted by the Region II model, which would be expected for near-threshold data. Fractographic analyses supported the influence of domains on crack growth behavior. The scatter in the Region I data appears to be contributed by the effects of domains and domain walls.