Effect of cast process and microalloying on the fracture toughness of Zr-based bulk amorphous alloys

In order to clarify the effects of tilt- or suction-cast processing and microalloying of minor Si on the three-point bending fracture toughness of the Zr-based bulk metallic glasses (BMGs), the tilt-cast and suction-cast Zr53-based and Zr48-based BMGs with and without Si were studied. The results revealed that the tilt-cast specimens present much better fracture toughness than the suction-cast counterparts as a result of their lower degrees of residual porosity. In addition, the microalloying of Si to 0.75 at.% in these BMGs would impose negative effects on their fracture toughness. The highest fracture toughness of 120 MPa m was achieved for the tilt-cast Zr₅₃Cu ₃₀Ni₉Al₈. Moreover, the morphology of fracture surface, the calculated fracture energy, and the Poisson's ratio show the similar trend to prove that the tilt-cast Zr-53 BMG without Si possesses the best fracture toughness among these BMGs in this study.