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

• The highest fracture toughness of 120 MPa m was achieved for the tilt-cast Zr53Cu30Ni9Al8.
• Shear bands in the tilt-cast Zr53Cu30Ni9Al8 plate (Fig. 7(a)) appear in a finer and denser manner.
• Tilt casting could effectively reduce the micro-porosity in the cast BMGs.
• Si minor addition would degrade appreciably the fracture toughness.

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 Zr53Cu30Ni9Al8. 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.

SEM micrographs of the tilt- and suction-cast samples where near the notch root after bending test; (a) Zr53Cu30Ni9Al8 and (b) (Zr53Cu30Ni9Al8)99.25Si0.75 are tilt-cast samples, (c) Zr53Cu30Ni9Al8 and (d) (Zr53Cu30Ni9Al8)99.25Si0.75 are suction-cast samples. Note that the tilt-cast Zr-53 BMG without Si possesses the best fracture toughness among these BMGs in this study.Figure optionsDownload as PowerPoint slide