Fatigue and fracture behavior of (Zr_(58)Ni_(13.6)Cu_(18)Al_(10.4))_(99)Nb_1 bulk-amorphous alloy

摘要

The fatigue and fracture behaviors of the (Zr_(58)Ni_(13.6)Cu_(18)Al_(10.4))_(99)Nb_1 bulk amorphous alloy are investigated by four-point-bend fatigue tests. The material shows a fatigue-endurance limit and fatigue ratio of 559 MPa and approx 0.328, respectively. The fracture toughness is estimated to be about 26-43 MPa m~(1/2). Shear bands were found to be oriented greater than 45 deg on the tension surface and smaller than 45 deg on the compression surface, with respect to the outer fiber-stress direction of the sample. The density of the shear bands on the tension side is greater than that on the compression side. Many wavy shear bands perpendicular to the outer fiber-stress direction also formed on the tension and compression surfaces during the fatigue process. The fracture surface can be divided into four regions: crack initiation, crack propagation, fast fracture, and melting regions. The fracture mechanism is discussed.