In this work Mg- and K-containing alanates have been investigated as possible hydrogen storage materials. Ball milling was carried out under argon or at moderate/high hydrogen pressure in order to obtain an improved driving force for the formation of potential new alanate phases. Powder X-ray diffraction and volumetric measurements were used in order to identify reaction mechanisms and phases forming in these systems. New unidentified peaks were detected for the mixtures 2MgH(2) + 3Al + KH and 2CaH(2) + Al + 2KH. However, they do not seem to belong to reversible hydride phases. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.