Effect of substitution Fe for Co on the cycle stability of AB5-type hydrogen storage alloys

The rare-earth-based AB(5)-type Mm(NiMnSiAl)(4.3)Co0.6-xFex (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) hydrogen storage alloys were prepared by casting and rapid quenching. The microstructures of the as-cast and quenched alloys were analyzed by XRD, SEM and TEM, and electrochemical cycle stability of the as-east and quenched alloys were measured. The effects of substitution Fe for Co on microstructures and electrochemical cycle stability of the as-east and quenched alloys were investigated in detail. The obtained results show that the effects of substitution Fe for Co on the phase structures of the as-cast and quenched alloys are imperceptible, but its effects on electrochemical cycle stability of the alloys are notable. The substitution Fe for Co can improve the cycle stability of the as-cast and quenched alloys. Especially, substitution Fe for Co can significantly enhance the cycle lives of the as-quenched alloys, which is mainly attributed to the grain refinement caused by substitution Fe for Co.