Effects of Remelting on the Microstructure and Absorption/Desorption Characteristics of MmNi4.8Al0.2 Hydrogen Storage Alloy

In this article, the effects of VIM and VAR remelting processes are investigated on the microstructure and absorption/desorption characteristics of MmNi4.8Al0.2 hydrogen storage alloy. The main alloy prepared in a Vacuum induction furnace and remelted in VIM and VAR. The microstructures and phases were analyzed with SEM and XRD. Hydrogen absorption/desorption characteristics is performed on Sievert apparatus. The results showed that the microstructure is consisting of matrix, second phase as a result of Al segregation, porosities and cracks. The second phases in the main alloy and VAR remelted have low content of La and Ce. This phase is solutionized or decreased to low level in VIM remelted alloy. Remelting, also, declined the absorption pressure to 21.55 and 18.17 bar and the desorption pressure to 7.13 and 5.49 bar in VAR and VIM remelted alloy, but increased the hydrogen storage capacity increased to 1.42 and 1.46 wt%  respectively. The more the homogeneity degree, the less the absorption/desorption pressure and the more the hydrogen storage capacity.