Fracture morphologies of Zr-based bulk metallic glasses under different stress states

KGaA, Weinheim. In the current study, the fracture morphologies of both Zr57Cu20Al10Ni8Ti5and Zr65Cu17.5Ni10Al7.5bulk metallic glasses (BMGs) under stress gradients are investigated using three-point bending tests, and are compared with conventional compressive and tensile tests. The findings show that, under compressive stress gradients, the fracture patterns consisting of cell-like vein patterns and radiating ridges are formed due to the inhibition of the instantaneous fracture process, during which a large amount of localized shearing occurs on the fracture plane. On the other hand, under tensile stress gradients, enlarged smooth regions and some transition zones have been observed on the fracture surfaces, indicating the achievement of more stable shearing processes before fracture. Correlations between the fracture surface features and the plastic deformation behavior of BMGs under different stress states are proposed and discussed. The findings are of significance in understanding the deformation and fracture mechanisms of BMGs under complex stress states. Fracture morphologies provide significant evidences in understanding the deformation and fracture mechanisms in bulk metallic glasses. When the applied uniform tensile stress is changed to a gradient distribution, the fracture surface shows enlarged smooth regions as well as the formation of some transition zones. The findings reveal that the stress gradient is able to confine the catastrophic failure of bulk metallic glasses.