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

A distinct glass transition and a rather wide supercooled liquid region bef ore crystallization were found in Ni-76 M-5 P-19 (M = Ti, Zr, Hf or Nb) ter nary amorphous alloys. The glass transition temperature (T-g) and the tempe rature interval of the supercooled liquid region defined by the difference between crystallization temperature (T,) and T,, Delta T-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 th an 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 t he 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 element s, and (3) negative heats of mixing among the main three elements. The tens ile fracture strength (ai) and Vickers hardness (H-v,) of the Ni-based amor phous alloys are in the ranges of 950 to 1500 MPa and 410 to 455, respectiv ely, which are considerably higher than those for the conventional Ni-based crystalline alloys. The finding of the Ni-based amorphous alloys with a wi de supercooled liquid region reaching about 50 K is promising for the futur e development of Ni-based bulk amorphous alloys with high strength and good ductility.