AMORPHOUS (TI, ZR, HF)-NI-CU TERNARY ALLOYS WITH A WIDE SUPERCOOLED LIQUID REGION

Ternary Ti-Ni-Cu, Zr-Ni-Cu and Hf-Ni-Cu amorphous alloys were found to exhibit a distinct glass transition combined with a rather wide supercooled liquid region before crystallization. The largest temperature interval of the supercooled liquid region defined by the difference between T(g) and T(x), i.e. DELTAT(x) (= T(x) - T(g)), is 55 K for Ti50Ni25Cu25, 60 K for Zr60Ni20Cu20 and 65 K for Hf60Ni20Cu20. These amorphous alloys with the largest DELTAT(x) values also exhibit the highest T(x) and the lowest melting temperature and crystallize through a single-stage exothermic reaction leading to the simultaneous precipitation of more than two kinds of compound. It is therefore presumed that the appearance of the wide supercooled liquid region before crystallization is due mainly to the necessity of the redistribution of the constituent elements for the precipitation of the compounds from the homogeneously mixed amorphous structure.