Effects of loading rates, notch root radius and specimen thickness on fracture toughness in bulk metallic glasses

摘要

The fracture toughness (K_Q) tests were carried out in order to study the effect of loading rate (K), notch root radius ? and specimen thickness (B) on the K_Q in Zr-based bulk glassy alloys (BGAs). The plane strain fracture toughness K_(IC) of the BMG of Zr_(50)Cu_(40)Ni_(10) at.% prepared by an arc tilt casting method showed a large value of 53 Mpa m~(1/2) under the conditions satisfying ASTM E399. With K of about 0.1 Mpam~(1/2) s~(-1), there were cases that the K_Q exhibited more than 100 MPa m~(1/2). The K_Q increased with increasing R even for smaller R of 30 μm and K_Q exhibited more than 120 MPam~(1/2) with R of more than 90 μm. K_Q decreases a little with decreasing the B from 2.3 to 0.12 mm was shown. In these cases, the estimated plane stress plastic zone sizes agreed well with the length of shear bands near the fatigue crack tips or notch roots on specimen surfaces.