Four-point-bending-fatigue behavior of the Cu45Zr45Ag7Al3 bulk metallic glass

Four-point-bend fatigue experiments were conducted on Cu45Zr45Ag7Al3 bulk metallic glass, which was done by the use of an electrohydraulic machine, at a frequency of 10 Hz (using a sinusoidal waveform) with an R ratio of 0.1, where R = σmin / σmax (σmin and σmax are the applied minimum and maximum stresses, respectively). This material shows a fatigue-endurance limit and fatigue ratio of 386 ± 5 MPa and 0.26 ± 0.01, respectively, and the fracture toughness is estimated to be about 23–30 MPa·m1/2. The fatigue-fracture morphology indicated that Cu45Zr45Ag7Al3 has a significantly brittle fracture mode. The fracture surface can be divided into four regions: crack initiation, crack propagation, fast fracture, and melting regions. The fracture mechanism is discussed.