Crystallization and mechanical behavior of (Hf, Zr)–Ti–Cu–Ni–Al metallic glasses

We have prepared a series of glass-forming alloys of composition (HfxZr1−x)52.5Cu17.9Ni14.6Al10Ti5 and (HfxZr1−x)57Cu20Ni8Al10Ti5 with x=0–1. The substitution of Hf for Zr reduces the glass-forming ability of these alloys; while all compositions of (HfxZr1−x)52.5Cu17.9Ni14.6Al10Ti5 can be cast in bulk form, amorphous samples of the Hf-rich compositions (x>0.8) of (HfxZr1−x)57Cu20Ni8Al10Ti5 can only be produced by rapid solidification. The alloys show similar crystallization behavior, although we observe an intermediate phase in the Hf-rich glasses (Al16Hf6Ni7) that is not observed in the Zr-rich glasses. The Young’s modulus and the flow strength under quasi-static uniaxial compression increase linearly with increasing Hf content. Under dynamic loading, the failure strength of all of the alloys tested decreases with increasing strain rate. The differences in mechanical behavior between the Zr- and Hf-rich glasses can be rationalized in terms of the higher melting point of Hf. The addition of Hf increases the average bond energy of the alloy, resulting in a higher modulus and increasing the activation energy for atomic motion by which plastic deformation occurs.