A 50-50 mixture of Mg and Ti was milled for different times, and the cycling discharge capacities of the resulting compounds were evaluated in KOH media. From Rietveld refinement analysis of the X-ray diffraction patterns, it is shown that a metastable hcp Mg50Ti50 compound is formed after 20h of milling. This material has a very low-electrochemical hydriding activity. However, in the presence of 10 wt.% Pd (added before milling), it displays a maximum discharge capacity of ca. 400 mAh g(-1) after three charge/discharge cycles. The irreversible structural evolution of the Mg50Ti50 alloy from a hcp phase to a fcc phase upon cycling is demonstrated. (c) 2007 Elsevier B.V. All rights reserved.