Comparison of the hydrogen absorption process in as-quenched and relaxed Zr50Ni50 glassy ribbons

Abstract

The time evolution of the hydrogen absorption of melt-quenched Zr 50 Ni 50 amorphous alloy ribbons was investigated for the as-quenched state and after a relaxation heat treatment. Hydriding was performed from the gas phase at 200 °C and 35 atm H 2 gas pressure for charging times up to t = 48 h. The absorption process was monitored by measuring the mass increase, the thermoelectric power and the magnetization of the hydrided ribbons. For both the as-quenched and relaxed state, homogeneously hydrided ribbons could only be obtained at small ( H M < 0.1 ) and high ( H M ≈ 1 ) hydrogen contents. The maximum amount of absorbed hydrogen was found to be the same for both states; however, the hydrogen absorption process in the relaxed ribbons required considerably longer times than for the as-quenched state. As in our previous study of a Zr 47.5 Ni 52.5 metallic glass, the magnetization measurements indicated also for the present alloy the occurrence of a phase separation process leading to the development of strongly magnetic nickel-rich clusters for long charging times.