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In this study, AZ61 alloy processed by equal channel angular pressing (ECAP) method, is presented. This research seeks to find out the relationship that exists between the microstructure of the AZ61-magnesium alloy doped with SiC and Ni and processed by ECAP in terms of hydrogen storage properties. The results indicate that grain size reduces nearly 10 times after 4 passes of ECAP. Homogeneous distribution of the SiC in the metal matrix composite (MMC) and dynamic recrystallization are also observed. There is a gradual reduction in the grain size when the number of ECAP passes are increased. This microstructural refinement induced by ECAP improves the storage capacity and reaction kinetics of the alloy. Besides, the addition of Ni catalyst achieves faster absorption and desorption kinetics. However, it does not change its capacity. Ni reacts with Mg to form an intermetallic, which is hydrogen-absorbing, which in turn, catalyzes the reaction. Apart from introducing defects, the ECAP process also produces Mg/Al intermetallic, which acts catalytically. It is shown that SiC-doped AZ61-magnesium alloy can absorb and desorb 6.8 wt% H 2 at 648 K and 50 atm. • AZ61 with SiC and Ni additives prepared by gravity stir casting method. • Dispersion characteristics of the particles influences the rate limiting factors. • AZ61-1 wt%SiC achieves a hydrogen capacity of 6.8 wt%. • Performance declines to 6.5 wt% when Ni catalyst is added. • Combining SiC and Ni shows improved kinetics. [ABSTRACT FROM AUTHOR]

In this study, commercial AZ31 Mg alloys were processed by equal channel angular pressing (ECAP) to study the effects of processing route and numbers of passes on hydrogen storage properties of AZ31 alloys. Furthermore, Mg-based metal matrix composites (MMCs) were fabricated by gravimetric casting of AZ31 alloy, activated carbon and Ni to investigate the effect of additives on hydrogen storage properties. The results indicated that kinetics of hydrogen uptake increased with the increasing number of pass. AZ31 processed by ECAP route B c with 8 passes had hydrogen capacity of 7.0 wt%, and demonstrated the highest grain refinement and the fastest hydrogen absorption kinetics. With the addition of 5 wt% of activated carbon and 0.5 wt% Ni, the hydrogen sorption kinetics of MMCs was enhanced and was comparable to that of the AZ31 processed by ECAP with 8 passes; however, in exchange for the improved kinetics, the hydrogen storage capacity was lowered to 6.3 wt%. To enhance hydrogen absorption kinetics, adding catalysts in the casting process could be more efficient than post-casting ECAP treatment if saving processing time is the priority. [ABSTRACT FROM AUTHOR]