Formation of Zr-based bulk metallic glass with large amount of yttrium addition

In this study, we systematically studied the effects of Y addition on the glass forming ability (GFA), thermal stability and mechanical property of Zr56Co28Al16 bulk metallic glass (BMG). The results show that two BMGs, i.e., Zr49Co28Al16Y7 and Zr46Co28Al16Y10 with diameters of at least 14 mm, were successfully prepared by the water quenching method. In addition, fully metallic glass ingot about 25 g can be obtained in the Zr46Co28Al16Y10 alloy by using the conventional arc-melting method. The origin of the high GFA of Zr46Co28Al16Y10) alloy was attributed to the smaller Gibbs free energy difference between the supercooled liquid state and crystalline state of the Zr46Co28Al16Y10 than that of Y-free alloy. On the other hand, the fracture strength of Zr-Co-Al-Y BMGs decreases with the increase of Y content. However, the Zr-Co-Al-Y BMGs containing 0-5 at.% Y still exhibit a high fracture strength of about 1690-1790 MPa. The fracture surface morphology of BMGs with 5-12 at.% Y shows a typical featureless mirror surface, implying the brittle deformation. This Zr-Co-Al-Y quaternary BMG could be regarded as a good candidate for developing a new series of BMGs.