The role of yttrium and oxygen on the crystallization behavior of a Cu-Zr-Al metallic glass

The crystallization behavior of Cu-Zr-Al alloys with different contents of oxygen and yttrium was studied. Three compositions were chosen based on the good glass former Cu-45Zr-8Al with varying Y contents (0, 03 and 2%) added to getter the oxygen from the glass. Melt spun ribbons were prepared and their crystallization behavior was analyzed by differential scanning calorimetry (DSC). Heat treatments were performed at selected temperatures based on the DSC data and the phases formed were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results revealed that oxygen has a strong influence on the crystallization behavior, it changes the mode and the phases formed and results in the formation of a metastable crystalline phase prior to the formation of the stable phases. The Y was found to have a more subtle effect: it lowers the incubation time for crystallization and promotes heterogeneous nucleation of Cu10Zr7 and, therefore, adding Y to these alloys has this important drawback that is reported for the first time here. The mechanisms by which each of these elements acts are suggested. Finally the formation of defects in the Cu10Zr7 phase is reported. (C) 2014 Elsevier B.V. All rights reserved.