Short range order and crystallization of Cu–Hf metallic glasses

Highlights: • Binary CuHf metallic glasses. • Glassy structure modelled by Reverse Monte Carlo simulation. • Voronoï tessellation analysis of local atomic arrangement. • Cu-centred clusters showing stronger ordering than Hf-centred ones. • Identified devitrification products. -- Abstract: Detailed information on the atomic arrangement of glassy Cu₅₄Hf₄₆, Cu₆₁Hf₃₉ and Cu₆₉Hf₃₁ alloys has been obtained by the reverse Monte Carlo (RMC) simulation using high-energy X-ray diffraction and neutron diffraction data as input. Dominant cluster units are identified by means of the radical Voronoï tessellation technique. Cu-centred clusters show a stronger ordering level than the Hf-centred ones. Results are compared with those previously reported for analogous binary amorphous systems such as Zr–Cu and Zr–Ni. Additionally, the thermal stability of the studied Cu–Hf alloys has been inspected by in-situ high-temperature X-ray diffraction and differential scanning calorimetry measurements. A different structural evolution is observed for Cu₆₉Hf₃₁ compared with Cu₅₄Hf₄₆ and Cu₆₁Hf₃₉. Products of devitrification are identified and quantified. The better glass forming ability of Cu₅₄Hf₄₆ and Cu₆₁Hf₃₉ compared with Cu₆₉Hf₃₁ is explained in the view of short range order differences of glassy states and corresponding crystalline phases formed during devitrification.