APFIM and TEM study of the oxygen behavior during crystallization of Zr65Cu27.5Al7.5 metallic glass

The influence of oxygen on the crystallization behavior of Zr65−xCu27.5Al7.5Ox (x=0.14, 0.43 and 0.82%) metallic glasses has been studied. The supercooled liquid regime (ΔTx) 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 Zr65Cu27.5Al7.5 suggesting that it is rich in Zr and O and is depleted in Cu.