Influence of oxygen on the crystallization behavior of Zr65Cu27.5Al7.5 and Zr66.7Cu33.3 metallic glasses

The influence of oxygen on the crystallization behavior of Zr-65 - xCu27.5Al7.5Ox (x = 0.14, 0.43 and 0.82) and Zr-66.7 (-) xCu33.3Ox (x = 0.14 and 0.82) metallic glasses has been studied. The supercooled liquid regime (Delta T-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 (Zr,Cu) 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 Zr-2(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 Zr-2(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. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.