A study was carried out into hydrogen decrepitation of Mg rich intermetallics, namely Mg2Ni and Mg2Cu. These intermetallics are quite similar to each other except for the fact that Mg2Ni hydrides directly forming Mg2NiH4, whereas Mg2Cu when hydrided disproportionates into a two-phase structure. A total of ten sorption cycles was applied to the alloys and the resulting size reductions were monitored. The results showed that Mg2Ni decrepitate quite fast with cycling, the greatest size reduction occurring within the first three cycles. The size reduction in Mg2Cu, on the other hand, was quite sluggish. This was attributed to the disproportionation of the alloy which involve more extensive diffusion of the metallic species, counteracting some decrepitating effect of cycling due to ensuing particle sintering and growth. (C) 2015 Elsevier B.V. All rights reserved.