Preparation of New Ni-based Amorphous Alloys with a Large Supercooled Liquid Region

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Abstract
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 (Tg) and the temperature interval of the supercooled liquid region defined by the difference between crystallization temperature (Tx) and Tg, ΔTx(=Tx−Tg) 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 (Tg⁄Tm) 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 (σf) and Vickers hardness (Hv) 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 Nibased 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.