On the scavenging and alloying effects of Y in the oxygen-contaminated Zr-based bulk metallic glass

The minor addition of yttrium (Y) is commonly employed to mitigate the negative impact of oxygen during the production of Zr-based bulk metallic glasses (BMGs). Nevertheless, the multifaceted roles of Y complicate the rapid identification of the optimal Y content necessary to improve both the glass forming ability (GFA) and the mechanical properties of oxygen-contaminated Zr-based BMGs. Here, we systematically investigated the effect of Y with different Y:O atomic ratios on GFA, mechanical properties, and microstructure of Zr₅₇Nb₅Al₁₀Cu_15.4Ni_12.6 BMG with oxygen content ranging from 480 at. ppm to 9600 at. ppm. It is found that Y added to oxygen-contaminated alloys initially removes oxygen from the matrix by forming Y₂O₃ until the Y:O ratio reaches 2:3, at which point the oxygen is almost exhausted, then the Y in excess of 2:3 will predominantly plays the role of alloying. The initial scavenging effect of Y improves the GFA and mechanical properties of oxygen-contaminated alloys; but the subsequent alloying of Y is harmful to the mechanical properties and GFA, thus giving the optimal Y content of oxygen-contaminated alloys, i.e., in Y:O ratio of 2:3. Furthermore, the effect of Y on the local atomic structure (crystal-like ordering structures) of the alloy is also discussed. The above findings are significant in promoting the commercial application of Y-doped Zr-based BMGs.