Structure study on rapidly solidified hydrogen storage alloy Zr(NiM)2.1

Molten alloy Zr(NiM)(2.1) (M=Mn, Cr, V) is rapidly solidified by melt spinning method with cooling rates of alloy ribbons between 4.35x10(5) Ks(-1) and 5.33x10(6) Ks(-1). The structure is analyzed by means of XRD and TEM. The data from XRD are further analyzed by the Rietveld method. The results show that all the rapidly solidified alloys with different cooling rates are composed only of micro-crystalline C14 Laves and C15 Laves phases, different from the appearance of the non-laves phase constituents Zr7M10 and Zr,Ni,, together with the C14 and C15 Laves phase in the slowly cooled master alloy. The C14 Laves phase in rapidly solidified alloys assumes a laminar structure, in which the dimensions of C14 Laves micro-crystallites are almost constant, 1 nm along the c direction and 3-4 nm along the a and b directions. The abundance of C14 Laves phase increases in rapidly solidified alloys as the cooling rate increases, and on the contrary, the abundance of C15 Laves phase decreases. When the cooling rate increases from 4.35x10(5) Ks(-1) to 5.33x10(6) Ks(-1), the abundance of C15 Laves phase decreases from 88.29 wt.% to 43.63 wt.%, and the crystallite size of C15 phase decreases from 54.1 nm to 17.8 nm. (C) 1999 Elsevier Science S.A. All rights reserved.