Study on hydrogenation behaviors of a Mg-13Y alloy

摘要

The Mg-13Y bulk alloy was prepared by conventional casting process and the Mg-13Y powder was processed by ball milling using the casting alloy under the protection of argon. The hydrogenation thermodynamics, hydrogenation process and phase transitions were carefully investigated in the Mg-13Y powder alloy. It is shown that the Mg-13Y casting alloy consists of Mg_(24)Y_5 phase and α-Mg containing yttrium which have different hydrogenation enthalpies, -195 kJ/mol H_2 (by calculation) and -42 kJ/mol H_2 (by Pressure -Composition-Temperature experiment), respectively. The structure evolution and phase transition in the Mg-13Y bulk alloy treated at 673 K and at 4 MPa for 40 h were observed by an optical microscopy (OM), a scanning electron microscopy (SEM), a transmission electron microscopy (TEM) and X-ray diffraction (XRD). The large Mg_(24)Y_5 phase in the bulk Mg-13Y alloy could be destroyed into fine cuboid-shaped YH_2 phases during the hydrogenation process, which is probably responsible for the improvement of mechanical properties of Mg-13Y alloy.