High-strength Cu-based bulk glassy alloys in Cu–Zr–Ti and Cu–Hf–Ti ternary systems Original Research Article

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 (Tg), crystallization temperature (Tx), and the supercooled liquid region ΔTx(=Tx−Tg) decrease for both Cu60Zr40−xTix and Cu60Hf40−xTix alloys. In contrast, the liquid temperature (Tl) has a minimum value of 1127 K for the Cu60Zr20Ti20 alloy and 1175 K for the Cu60Hf20Ti20 alloy, resulting in a maximum Tg/Tl of 0.63 and 0.62, respectively. The alloys with the highest Tg/Tl 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.