Elastic properties of intermetallic AB2 and AB5 hydrogen-absorbing compounds

Abstract

The elastic properties of AB2 and AB5 hydrogen-absorbing intermetallic compounds are reviewed. The relevance of these properties to hydrogen absorption is discussed briefly. In many cases the temperature dependence of the elastic constants of the AB2 compounds is anomalous in that the moduli do not decrease monotonically with increasing temperature. This unusual behavior appears to be associated with electronic structure effects in a number of cases. The absorption of hydrogen by polycrystalline TaV2 has a profound effect on the aggregate shear modulus, changing both the magnitude and temperature dependence significantly. This effect of hydrogen on the mechanical properties appears to occur via effects on the electronic structure. Few measurements of elastic properties have been reported for hydrogen-absorbing AB5 intermetallic compounds. The LaAlxNi5−x system has been investigated by means of measurements on polycrystals prepared by hot isostatic pressing. The moduli decrease about 8% as x increases from 0 to 1.