Influence of oxygen on the crystallization behavior of Zr₆₅Cu_27.5Al_7.5 and Zr_66.7Cu_33.3 metallic glasses

Abstract

The influence of oxygen on the crystallization behavior of Zr_65−xCu_27.5A_l7.5O_x (x=0.14, 0.43 and 0.82) and Zr_66.7−xCu_33.3O_x (x=0.14 and 0.82) metallic glasses has been studied. The supercooled liquid regime (ΔT_x) decreases with increase in oxygen content for the Zr-Cu-Al alloy, while it increases for the Zr-Cu metallic glass. In the case of the Zr-Cu metallic glass, the crystallization product (Zr₂Cu) is not influenced by the oxygen content, while in Zr-Cu-Al alloys the oxygen level has a strong influence on the crystallization sequence. At low oxygen level (x=0.14), the ternary glass crystallizes polymorphously to Zr₂(Cu,Al). At higher oxygen content, the ternary amorphous alloy crystallizes in two stages by primary crystallization into an icosahedral phase and subsequently to the stable Zr₂(Cu,Al) phase. Three-dimensional atom probe results have shown that the composition of the icosahedral and amorphous phases is close to Zr₇₅Cu₁₅Al₅O₅ and Zr₆₂Cu₂₄Al₁₄, respectively.