Microstructure and protium absorbing/desorbing characteristics of Mg2Ni-Mnalloys

The protium absorbing/desorbing characteristics of the rapidly-solidified a nd mechanic ally-ground Mg2Ni-Mn alloys with different Manganese content we re investigated. High Manganese additions do not result in great changes in plateau pressure Of Mg2Ni phase. But in mechanically-ground specimens of M anganese-added alloys, a new plateau appears during absorption of protium a t a pressure higher than the plateau pressure Of Mg2Ni phase. In rapidly-so lidi fled and mechanically-ground specimens of Manganese-added alloys, prot ium content at low temperature increases. By exposing specimens for many ho urs in argon atmosphere at room temperature after hydriding at 250 degreesC , the desorbed protium content increases and the protium desorption tempera ture decreases. This implies that the amount of microtwinning decreases wit h increasing elapsed time, and then protium desorbing temperature changes t o lower values. Formed MgH2 phase in high Manganese-added alloys desorbs pr otium at low temperature probably due to contractive strain generated at th e interface between the MgH2 phase and intermingled Mg2NiH4 phase as the la ter desorbs protium.