Preparation of new Ni-based amorphous alloys with a large supercooled liquid region

A distinct glass transition and a rather wide supercooled liquid region before crystallization were found in Ni₇₆M₅P₁₉ (M=Ti, Zr, Hf or Nb) ternary amorphous alloys. The glass transition temperature (T_g) and the temperature interval of the supercooled liquid region defined by the difference between crystallization temperature (T_x) and T_g, ΔT_x(=T_x-T_g) are 659 and 48 K for the M=Ti alloy, 675 and 34 K for the Zr alloy, 687 and 34 K for the Hf alloy, and 668 and 21 K for the Nb alloy, respectively. The reduced glass transition temperature (T_g/T_m) shows high values higher than 0.60 for the Ni₇₆M₅P₁₉ (M=Ti and Hf) alloys. The high stability of the supercooled liquid against crystallization is due to the satisfaction of the three empirical rules for achievement of high glass-forming ability, i.e., (1) multi-component alloy systems consisting of more than three elements, (2) significant atomic size ratios above 10% among the main three elements, and (3) negative heats of mixing among the main three elements. The tensile fracture strength (σ_f) and Vickers hardness (H_v) of the Ni-based amorphous alloys are in the ranges of 950 to 1500 MPa and 410 to 455, respectively, which are considerably higher than those for the conventional Ni-based crystalline alloys. The finding of the Ni-based amorphous alloys with a wide supercooled liquid region reaching about 50 K is promising for the future development of Ni-based bulk amorphous alloys with high strength and good ductility.