Effect of Hf substitution Cu on glass-forming ability, mechanical properties and corrosion resistance of Ni-free Zr–Ti–Cu–Al bulk metallic glasses

A series of Ni-free Zr55Ti3HfxCu32-xAl10 (x = 0, 1, 2, 3, 4, 5 at. %) bulk metallic glasses (BMGs) were developed by copper mold suction-casting. The effect of partially substituting Cu by Hf was investigated in terms of glass-forming ability (GFA), mechanical properties, and corrosion behavior. As a result of the partial substitution, the GFA of Hf-bearing amorphous alloys were significantly enhanced as compared to Zr55Ti3Cu32Al10 BMGs. Hf addition also enlarged the supercooled liquid region from 55 K to 70 K. The critical diameter was found to increase from 4 mm to 8 mm for x = 3. The corresponding compressive yield strength was over 1800 ± 21 MPa with a large plastic strain above 2.60 ± 0.10%. Electrochemical tests indicated that the lowest corrosion current density was 1.6 ± 0.1 × 10−8 A/cm2 for the alloy with x = 5 in H2SO4 solution, thereby yielding a superior corrosion resistance.