Relaxation and crystallization of amorphous Zr65Al7.5Cu17.5Ni10

The structural development of amorphous Zr65Al7.5Cu17.5Ni10 obtained by rapid quenching was investigated after annealing and at elevated temperatures by means of X-ray diffraction (XRD) and differential scanning calorimetry measurement (DSC). The interference functions of the metallic alloy in the undercooled liquid as well as in the amorphous state were determined. The results confirm experimentally that the amorphous structure represents the frozen in undercooled liquid state. Structural relaxation of the as-quenched state was observed at annealing temperatures T-A below and above the glass transition temperature T-g = 630 K. The calculated pair correlation functions, representing mainly the Zr-Zr distribution, show the behaviour typically for metallic glasses at a first maximum of r(1) = 3.11 Angstrom (nearest neighbour distance similar to atomic diameter) and a split sec-end peak in G(r). The crystallization appears after a temperature dependent incubation time r. The crystallization is characterized by the simultaneous formation of several phases, mainly tetragonal CuZr2 and further unknown phases. The phase composition was found to be dependent on the annealing conditions. Continuous heating with heating rates greater than 5 K min(-1) and annealing at temperatures T-A > 720 K lead to the formation of an additional metastable cubic NiZr2-type phase. (C) 1997 Elsevier Science S.A.