Increasing costs and the limited availability of fossil oil resources, as well as the necessity to reduce pollution of the environment, demand a change in energy sources, especially for cars. A renewable clean energy source has been found with hydrogen, which releases large amounts of energy from a well controlled reaction with oxygen to form water. Highly efficier1t fuel cells have been developed to host this reaction. Still challenging, however, is the safe and efficiet1t storage of hydrogen. Magnesium-nickel alloys (such as Mg-14Ni) have a high hydrogen storage capacity and improve the sorption kinetics.
The present project investigated the performance of aluminium in Mg-14Ni in causing age-hardenability, as this can lead to finely dispersed precipitations which may improve the catalytic effect of Mg2Ni. The experiments conducted clearly demonstrate that Mg- 14Ni-5AI and Mg-14Ni-10AI are age-hardenable at elevated temperatures. Microstructural analyses, however, showed that the aluminium contents cause the development of AINi. This phase develops during melting and causes significant difficulties due to very high melt viscosity. The development of Al Ni at the cost of Mg2Ni is likely not beneficial to hydrogen storage properties.
Barium, zirconium and strontium, common modifiers in similar alloy systems, were tested for their performance in the magnesium-nickel-aluminium system. Only barium improves the microstructure with respect to hydrogen storage; zirconium diminishes the effects of aluminium. Strontium modification did not lead to useful results in an evaluation of its performance, as it was accompanied by a drastic change of composition.