The effect of rapid solidification on the microstructure and hydrogen storage properties of V35Ti25Cr40 hydrogen storage alloy

The microstructures and hydrogen storage properties of as-cast and rapidly solidified V35Ti25Cr40 alloys have been investigated in this paper. The results showed that the rapid solidification refined the dendritic microstructure and altered the element distribution of the alloy. And through the positron annihilation measurements of the vacancy trapping rate (K-d1) and vacancy-trapped positron annihilation lifetime (tau(2)), it was found that the rapid solidification increased the vacancy concentration and at the same time decreased the vacancy size in the alloy. The XRD results showed that the rapid solidification also significantly enlarged the alloy's lattice parameter. As a result of the microstructure change, the hydrogen absorption capacity and hydrogen absorption rate were increased; and the kinetic mechanism of hydrogen absorption was changed from 3-D diffusion control in the as-cast alloy to chemical reaction control in the rapidly solidified alloy; but the activation property was to some extent weakened after the rapid solidification. (c) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.