Formation and mechanical properties of Cu-Hf-Ti bulk glassy alloys

High-strength Cu-based bulk glassy alloys were formed in the Cu-Hf-Ti system by the copper mold casting and melt clamp forging methods. The maximum diameter is 4 mm for the Cu60Hf25Ti1.5 alloy. The substitution of Hf in the Cu60Hf40 alloy by Ti causes an increase in the glass-forming ability (GFA). As the Ti content increases, the glass transition temperature (T-g) decreases, while the crystallization temperature (T-x) shows a maximum at 5% Ti and then decreases, resulting in a maximum supercooled liquid region DeltaT(x) (= T-x - T-g) of 78 K at 5% Ti. The liquidus temperature (T-1) has a minimum of 1172 K around 20% Ti, and hence, a maximum T-g/T-l of 0.62 is obtained at 20% Ti. The high GFA was obtained at the compositions with high T-g/T-l,. The bulk glassy alloy exhibits tensile fracture strength of 2130 MPa, compressive fracture strength of 2160 MPa, and compressive plastic elongation of 0.8 to 1.6%. The new Cu-based bulk glassy alloys with high; T-g/T-l above 0.60, high fracture strength above 2100 MPa, and distinct plastic elongation are encouraging for future development as a new type of bulk glassy alloy that can be used for structural materials.