Experimental investigation and thermodynamic modeling of the phase equilibria at the Mg-Ni side in the La-Mg-Ni ternary system

The La-Mg-Ni system is considered as one of the most promising candidates for the hydrogen storage alloys, and most of hydrogen storage phases in the La-Mg-Ni ternary system are mainly located near the Mg-Ni side. The present work focused on clarifying the phase relationships at the Mg-Ni side using the Calphad method. The thermodynamic descriptions of phase relationship were established on the available literature data together with our experimental results. Several key specimens were selected, synthesized and annealed at 773 K, 973 K and 1173 K to confirm the accuracy of the phase diagram calculated from the ternary thermodynamic description. Inductively coupled plasma, X-ray diffraction and scanning electron microscopy with electron dispersive spectrometry were used to analyze the alloys. The acceptable agreement on the equilibrium phases between the experimental and calculated results suggested the reliability of the assessed thermodynamic descriptions of phase relationship. The optimized phase equilibrium and thermodynamic information were successfully used to discuss the synthesized technological parameter of the La-Mg-Ni hydrogen storage alloys. (C) 2010 Elsevier B.V. All rights reserved.