Composition optimization of the Cu-based Cu–Zr–Al alloys

The present paper is concerned with the formation of the Cu-based Cu–Zr–Al bulk metallic glasses (BMGs). Composition optimization for BMG formation was realized by using an ‘e/a-variant criterion’ that had been successfully applied in the Zr–Al–Ni and Zr–Al–Co systems. This criterion was incorporated into the ternary phase diagram by constructing a composition line (Cu61.8Zr38.2)1−xAlx, which was defined by linking the optimum binary composition (Cu61.8Zr38.2, a deep eutectic in this case) and the third element. BMGs were obtained within an e/a span from 1.24 to 1.3 along this composition line. Thermal analysis results indicate that these BMGs manifest increased thermal stability and glass forming ability (GFA) with increasing e/a ratios. The maximum appears in Cu58.1Zr35.9Al6 with the e/a value of 1.3 which is the highest among our samples. The characteristic thermal parameters of this BMG are Tg=760 K, Tg/Tl=0.648, which are all superior to those reported for the known Cu55Zr40Al5 BMG.