Bulk amorphous alloys: Preparation and properties of (Mg0.98Al0.02)x(Cu0.75Y0.25)100-x

New bulk amorphous quaternary alloys of the composition (Mg1-xAlx)60Cu30Y10 (x = 0-0.17) were recently reported by the authors and preliminary results of the influence of Al content on the ability to form a bulk amorphous phase were presented. In the present note we extend this work to look for the influence of the Mg-Al content on the glass forming ability by studying a range of compositions, (Mg0.98Al0.02)x(Cu0.75Y0.25)100-x for x = 60-80 at.%. As previously, the alloys were prepared by a relatively simple technique, i.e. rapid cooling of the melt in a wedge-shaped copper mould. This method provides a range of cooling rates within a single ingot during the solidification that link the slowly and rapidly cooled microstructure for each alloy composition. Hence, the maximum thickness of the amorphous part of the cast material will be a measure of the glass forming ability (GFA) of the particular alloy. X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC) have been used to investigate the structure and the various structural transitions in the alloys. One observation is that the GFA decreases with increasing content of (Mg0.98Al0.02)x. For x > approximately 75 at.% no amorphous phase is formed. Based on these measurements a phase diagram was constructed.