Formation, thermal stability and mechanical properties of (Cu_0.6Zr_0.3Ti_0.1)_100-xM_x (M=Fe, Co, Ni) bulk glassy alloys

New Cu-based bulk glassy alloys exhibiting a large supercooled liquid region and good mechanical properties were formed in Cu-Zr-Ti-M (M=Fe, Co or Ni) systems by copper mold casting. The maximum diameter for glass formation was up to 4 mm for the Cu-Zr-Ti-Ni alloys. The addition of Co or Ni element caused an extension of a supercooled liquid region (ΔT_x = T_x - T_g) from 38K for Cu₆₀Zr₃₀Ti₁₀ to 54 K for (Cu_0.6Zr_0.3Ti_0.1)₉₅Co₅ and 60 K for (Cu_0.6Zr_0.3Ti_0.1)₉₅Ni₅, accompanying the change in the crystallization mode from two stages to a single stage. The crystallization of the 5%Ni alloy occurs through the direct precipitation of a metastable (Cu,Ni)₁₀(Zr,Ti)₇ phase from the supercooled liquid. The compressive fracture strength (σ_c,f) and plastic strain (ε_p) are in the range of 1830 to 2030 MPa and 0.3 to 1.7%, respectively, for the 1 to 4%Fe alloys, 1900 to 1920 MPa and 1.0 to 1.2%, respectively, for the 1 to 5%Co alloys and 1900 to 1960 MPa and 0.6 to 1.9%, respectively, for the 1 to 6%Ni alloys. The best combination of σ_c,f and ε_p was 2030 MPa and 1.7%, respectively, for the 2.5%Fe alloy. These favorable properties of the Cu-Zr-Ti-M (M=Fe, Co or Ni) bulk glassy alloys are promising for future practical use as a high-strength engineering material.