Influence of oxygen on the crystallization behavior of Zr65Cu27.5Al7.5 andZr66.7Cu33.3 metallic glasses

The influence of oxygen on the crystallization behavior of Zr-65 - xCu27.5A l7.5Ox (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, whi le it increases for the Zr-Cu metallic glass. In the case of the Zr-Cu meta llic glass, the crystallization product (Zr,Cu) is not influenced by the ox ygen content, while in Zr-Cu-Al alloys the oxygen level has a strong influe nce on the crystallization sequence. At low oxygen level (x = 0.14), the te rnary glass crystallizes polymorphously to Zr-2(Cu,Al). At higher oxygen co ntent, the ternary amorphous alloy crystallizes in two stages by primary cr ystallization into an icosahedral phase and subsequently to the stable Zr-2 (Cu,Al) phase. Three-dimensional atom probe results have shown that the com position of the icosahedral and amorphous phases is close to Zr75Cu15Al5O5 and Zr62Cu24Al14, respectively. (C) 2000 Acta Metallurgica Inc. Published b y Elsevier Science Ltd. All rights reserved.