Mechanisms and Mechanics of Fatigue Crack Propagation in Zr-Based Bulk Metallic Glass

Abstract

In the present study, the fatigue crack propagation tests of Zr-based metallic glass were conducted in laboratory air, and the fracture surface was observed to clarify the effects of loading frequency and the stress ratio. In spite of being brittle material, the metallic glass showed stable fatigue crack propagation behaviour, and the relationship between the crack propagation rate, da/dN, and the stress intensity range, K, can be divided into three regions as well as conventional crystalline metals. The crack propagation rate can be expressed as a function of the stress intensity range by Paris law in the middle region. The power in Paris law was 1.4, and it is considerably smaller than the value for conventional crystalline metals. The threshold stress intensity range, Kth, was 1.8 MPam1/2. The effects of the stress ratio and the loading frequency were not observed on the relationships, da/dN-K and da/dN-Keff. Then, the fatigue crack propagation of the metallic glass is cycle dependent in laboratory air.