Thermal stability, corrosion resistance, and surface analysis of Cu–Hf–Ti–Ni–Nb bulk metallic glasses

Bulk metallic glasses (BMGs) with high thermal stability and good corrosion resistance were synthesized in the (Cu_0.6Hf_0.25Ti_0.15)_100−x−yNi_yNb_x system by copper mold casting. The addition of Ni element causes an extension of a supercooled liquid region (ΔT_x = T_x – T_g) from 60 K for Cu₆₀Hf₂₅Ti₁₅ to 70 K for (Cu_0.6Hf_0.25Ti_0.15)₉₅Ni₅. The simultaneous addition of Ni and Nb to the alloy is effective in improving synergistically the corrosion resistance in 1 N HCl, 3 mass% NaCl, and 1 N H₂SO₄ + 0.01 N NaCl solutions. The highly protective Hf-, Ti-, and Nb-enriched surface film is formed by the rapid initial preferential dissolution of Cu and Ni, which is responsible for the high corrosion resistance of the alloys in the solutions examined.