Thermal stability of hydride phase obtained by mechanical treatment of Mg-10 mass% Fe in hydrogen under pressure

The formation of hydride phases under high-energy ball-milling of Mg and Mg+10 mass% Fe powders in hydrogen under a pressure of 1.2 MPa has been studied. The influence of iron content and dispersion degree of the Mg-alloys upon thermal stability and decomposition temperature of the hydride phase of the alloys was investigated by thermal desorption, x-ray diffraction, and differential thermal analyses. It was established that addition of 10 mass% of iron to magnesium contributes to higher dispersion degree of the magnesium hydride obtained via milling in hydrogen under pressure. The hydride contains maximum amount of weak- and medium-bound hydrogen. The latter is mainly concentrated in the region of grain boundaries, the quantity of which increases with increase in dispersion degree. The formation of new boundaries and accumulation of defects in these regions are accompanied by an increase in thermodynamic potential, which causes a decrease in both the temperature of decomposition of the hydride phase by 100 deg C and its thermal stability.