Hydriding properties of the ternary Mm-based AB(5) alloys modified by surface treatment

The surface treatment (F-treatment technique) effects on the hydriding properties of MmNi(1-x)Mx ternary alloys (where Mm is mischmetal) by substituting small amounts of Al, Cu, Fe and Mn for Ni are investigated in this paper. The properties studied include metallographic microstructure, P-C-T properties, initial activation characteristics and long-term storability by air-exposure. It was found that Al-, Cu-, Fe- and Mn-substitutions can lower the plateau pressure and decrease the hysteresis of MmNi, but cannot completely lower the former to the level of LaNi5 without loss of H-capacity. The F-treatment can improve initial activation of all the substituted ternary alloys under moderate conditions and also provide strong resistance against air-exposure even after 6 months.