Thermal Stability and Mechanical Strength of Bulk Glassy Ni-Nb-Ti-Zr Alloys

Abstract

Bulk glassy Ni-based alloys with high fracture strength exceeding 2700 MPa were prepared in Ni₆₀Nb_40−x−yTi_xZr_y system by copper mold casting. The glassy alloys with distinct glass transition were obtained in the wide composition range from 0 to 35%Ti and 0 to 30%Zr and the largest supercooled liquid region before crystallization was 76 K for Ni₆₀Nb₁₅Ti₁₀Zr₁₅. The maximum diameter was 2 mm for Ni₆₀Nb₂₀Ti₁₅Zr₅ and the glass transition temperature (T_g), crystallization temperature (T_x) and reduced glass transition temperature (T_g⁄T_l) of the bulk glassy alloy were 841 K, 898 K and 0.61, respectively. The Young’s modulus (E), compressive fracture strength (σ_c,f) and compressive fracture elongation (ε_c,f) were 156 GPa, 2770 MPa and 2.4%, respectively, for the bulk alloy. There is a tendency for fracture strength to increase with increasing E, T_g and liquidus temperature (T_l). It is therefore interpreted that the high strength is due to strong bonding nature among the constituent elements.