Rapidly quenched amorphous Mg65Ni20Cu5Y10 metallic glass compacts were subjected to heavy shear deformation by high-pressure torsion until different amounts of ultimate strain. High-resolution X-ray diffraction analysis and scanning electron microscopy revealed that high-pressure torsion resulted in a deformation dependent microstructure. High-pressure calorimetry measurements revealed that hydrogen uptake in the fully amorphous alloy occurs at a significantly lower temperature compared to the fully crystallized state, while the amount of absorbed hydrogen increased considerably after heavy shear deformation due to the formation of Mg2Ni crystals. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.