ELECTRON-MICROSCOPY AND X-RAY-DIFFRACTION STUDIES OF RAPIDLY QUENCHED ZR-NI AND HF-NI RIBBONS WITH ABOUT 90 AT PERCENT NI

The structure of melt-spun ribbons of the alloys Zr9Ni91, Zr10Ni90 and Hf11Ni89 was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Ribbons of the Zr9Ni91 and Zr10Ni90 alloys prepared at a high cooling rate (ribbon thickness d = 11 mum) were characterized by an amorphous matrix with a few per cent of quenched-in crystallites. The ribbon of the Hf11Ni89 alloy prepared with the same thickness (i.e. at the same cooling rate) exhibited a nanocrystalline grain structure of the HfNi5 phase. Thicker ribbons of the Zr9Ni91 alloy (d = 17-22 mum), for which the quench rate was correspondingly lower, were obtained as a b.c.c. Ni(Zr) solid solution phase with a grain size of nearly 1 mum. A high resolution (HR) TEM study of one of the Zr9Ni91 crystalline ribbons revealed a fine structure of the interior of the crystallites which can be attributed to an ordering on the Zr sublattice over distances of several nanometres within the b.c.c. grains.