Alternative Strain Aging Effect for Fatigue of Ductile Bulk Glassy Alloys

抄録

The metal fatigue mechanism of bulk glassy alloys (BGAs) resulting from the ductile nature of a glassy alloy differs from that of the conventional crystalline engineering alloys. Extreme hardening of the fatigue crack tip on the fatigue-fractured surface of the Zr- and Pd-based BGAs was usually observed just before the final fracture. Embrittlement around the fatigue crack tip, generated by excessive hardening to stop the fatigue crack propagation, significantly decreases fatigue fracture toughness. Hardening by hydrogen was also considered as an alternative mechanism of the strain aging effect in fatigue of glassy alloys because the second phase cannot be observed on a fatigue fracture surface, and only hydrogen promotes hardening, maintaining a glass structure. Hydrogen analysis of a micro area region was attempted with nuclear reaction analysis which used accelerated ion ¹⁵N up to 6.385 MeV to determine the hydrogen concentration of the fatigue-fracture surface. We successfully measured the characteristic enrichment of hydrogen near the fatigue-fracture surface.