The mixtures of scandium hydride ScH2 and metal boride MBn, which is MgB2 or CaB6, were hydrogenated by mechanical milling under hydrogen pressure at room temperature. ScH2-MgB2 and ScH2-CaB6 desorbed 3.4 and 2.3 mass% of H-2, respectively, with peaks below 300 degrees C. The results of synchrotron radiation X-ray powder diffraction and X-ray absorption spectroscopy at the Sc K-edge indicated that ScB2 was produced by milling. Fourier-transform infrared spectroscopy suggested that hydrogen was stored as B-H bonds in the as-milled samples. Nuclear magnetic resonance spectroscopy clarified the presence of metal borohydrides M(BH4)(2) (M = Mg and Ca) in the as-milled ScH2-MBn mixtures. These results indicate that M(BH4)(2) is synthesized by milling the ScH2-MBn mixtures under hydrogen pressure at room temperature, and hydrogen was desorbed from M(BH4)(2). The by-products of M(BH4)(2) are MgH2 in the M = Mg case, which was observed by transmission electron microscopy, and ScB2 in both cases. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.