AbstractUsing transmission electron microscopy (TEM) and electron microdiffraction with the radiolysis effect and a series of calibration images of TEM obtained for single-phase MgH2 samples at different exposure times, we studied the topological features of the microstructure of powder hydrogen-sorbing composites based on the Mg89Ni11 eutectic alloy. It was found that after several hydrogenation–dehydrogenation cycles the composite retains a highly dispersed microstructure: in the regions of composite samples with a cross-sectional area of 1 μm2 there are grains of Mg and Mg2Ni hydride-forming phases that are in direct contact, which improves the hydrogen-sorbing characteristics of the composite.