Formation, Thermal Stability and Mechanical Properties of (Cu<SUB>0.6</SUB>Zr<SUB>0.3</SUB>Ti<SUB>0.1</SUB>)<SUB>100-x</SUB>M<SUB>x</SUB> (M=Fe, Co, Ni) Bulk Glassy Alloys

Abstract

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 38 K for Cu 60 Zr 30 Ti 10 to 54 K for (Cu 0.6 Zr 0.3 Ti 0.1 ) 95 Co 5 and 60 K for (Cu 0.6 Zr 0.3 Ti 0.1 ) 95 Ni 5 , 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 (ep) 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 e 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.