Effect of Minor Addition of Oxygen on Bulk Metallic Glass Formation of Binary Cu-Zr Alloys via Containerless Processing

The effect of oxygen content on the glass-forming ability of binary Cu-Zr alloys is investigated by the in situ observation of the cooling process during the containerless solidification using an aerodynamic levitation technique. The oxygen content of approximate to 0.72 at% induces the crystallization of undercooled liquid Cu(47)Zr(53)alloy, whereas that of approximate to 0.33 at% enhances the glass-forming ability and leads to the formation of bulk metallic glass when compared with the alloy containing approximate to 0.20 at% of oxygen. The differential thermal analysis of the bulk metallic glass samples shows the extension of the undercooled liquid region with an increase in the oxygen content from 0.20 to 0.33 at% in the Cu(47)Zr(53)alloy. Time-resolved synchrotron X-ray diffraction experiments reveal structure evolution of the Cu(47)Zr(53)alloy from the undercooled liquid to glass or crystal. The effect of oxygen on the glass-forming ability is qualitatively described in terms of reducing the critical cooling rate of the alloy.