Glass transition, viscosity of the supercooled liquid and crystallization behaviour of Zr-Al-Cu-Ni-Fe metallic glasses

The effect of iron on the glass transition, the viscosity of the supercoole d liquid and the crystallization behaviour of (Zr0.650Al0.075Cu0.175Ni0.100 )(100-x)Fe-x and (Zr0.55Al0.10Cu0.30Ni0.05)(100-x)Fe-x metallic glasses (0 less than or equal to x less than or equal to 15) was investigated using pa rallel plate rheometry, differential scanning calorimetry and X-ray diffrac tion. Iron additions shift the glass transition as well as the crystallizat ion to higher temperatures, and increase the viscosity of the supercooled l iquid. Increasing iron content reduces the extension of the supercooled liq uid region. This mainly results from a stronger composition dependence of t he glass transition than the crystallization temperature. The results are d iscussed with respect to the kinetics and thermodynamics of the supercooled liquid suggesting that changes in the atomic arrangement and in the free v olume are the microscopic origin for the differences in the viscosity and t he thermal stability of the alloys. All investigated alloys are rather stro ng glasses as expressed by a relatively high melt viscosity, a low Vogel-Fu lcher Tammann (VFT) temperature and a rather high fragility parameter, but in general (Zr0.55Al0.10Cu0.30Ni0.05)(100-x)Fe-x alloys are slightly strong er glasses than (Zr0.650Al0.075CU0.175Ni0.100)(100-x)Fe-x alloys.