High-strength Cu-based bulk glassy alloys in Cu-Zr-Ti and Cu-Hf-Ti ternary systems

New Cu-based bulk glassy alloys were formed in Cu-Zr-Ti and Cu-Hf-Ti systems by the copper mold casting method. The critical diameter is 4 mm for the Cu60Zr30Ti10 and Cu60Hf25Ti15 alloys which are larger than 1 mm for the Cu60Zr40 and Cu60Hf40 glassy alloys. The substitution of Zr or Hf for Ti causes an increase in the glass-forming ability (GFA). As the Ti content increases, the glass transition temperature (T-g), crystallization temperature (T-x), and the supercooled liquid region DeltaT(x)( = T-x-T-g) decrease for both Cu60Zr40-xTix and Cu60Hf40-xTix alloys. In contrast, the liquid temperature (T-l) has a minimum value of 1127 K for the Cu60Zr20Ti20 alloy and 1175 K for the Cu60Hf20T20 alloy, resulting in a maximum T-g/T-l of 0.63 and 0.62, respectively. The alloys with the highest T-g/T-l value showed the highest GFA for these Cu-based alloys. The bulk glassy alloys exhibit high tensile fracture strength of 2000-2160 MPa, compressive fracture strength of 2060-2150 MPa and compressive plastic elongations of 0.8-1.7%. The finding of the new Cu-based bulk glassy alloys with high GFA, high fracture strength above 2000 MPa and distinct plastic elongation is encouraging for the future development of a new type of bulk glassy alloy which can be used for structural materials, (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.