APFIM and TEM study of the oxygen behavior during crystallization of Zr₆₅Cu_27.5Al_7.5 metallic glass

Abstract

The influence of oxygen on the crystallization behavior of Zr_65-xCu_27.5Al_7.5O_x (x=0.14, 0.43 and 0.82%) metallic glasses has been studied. The supercooled liquid regime (ΔT_x) decreases with increase in oxygen. At low oxygen level (0.14%), the alloy crystallizes in a single stage by the formation of Zr₂(Cu, Al). At higher oxygen content, the amorphous phase crystallizes in two stages by the precipitation of a quasicrystalline phase first and subsequently the stable Zr₂(Cu, Al). The present paper is the first evidence of icosahedral phase formation in ternary Zr-Cu-Al system. The temperature and time window for the formation of quasicrystalline phase is quite narrow. Three-dimensional atom probe studies have shown that the quasicrystalline phase has a composition of Zr₆₅Cu_27.5Al_7.5 suggesting that it is rich in Zr and O and is depleted in Cu.