Metallic glass formation in the binary Cu–Hf system

Glass formation, structure and thermal properties of alloys in the binary Cu_100−x Hf _x alloy system, where x = 25–50 at.%, are reported and discussed. This work also presents a comparison between copper casting techniques, from thick melt-spun ribbons to suction cast cylindrical rods, and the prediction of critical diameter, d _c, based on maximum ribbon thickness, x _c. Ribbons of Cu₆₀Hf₄₀ and Cu₆₅Hf₃₅ exhibited a fully glassy phase up to a thickness of 170 μm. Suction casting lead to an increase in the largest diameter over which both alloys could be cast, in comparison to melt-spun ribbons, and remain amorphous, with Cu₆₅Hf₃₅ showing a large critical diameter of 1 mm. This result is rationalised by a lower liquidus temperature, T _l, which maximises the reduced glass transition temperature, T _rg, and also correlates closely with the eutectic point. Finally, there were remarkable similarities between the Miedema model and the efficient packing model for predicting the range for metallic glass formation in this binary system.