Magnesium-based hydrogen storage materials are promising candidates for hydrogen storage due to their high storage density and environmentally friendly properties. However, the high dehydrogenation enthalpy change (approximately 75 kJ/mol H₂) and high dehydrogenation temperature (573 K at 0.1 MPa) of MgH₂, limits the engineering application of Mg/MgH₂ as a hydrogen storage material. This work reviews the prediction models and methods of enthalpy changes for hydriding/dehydriding (H/D) reactions in order to find out the ideas and ways to reduce them. The mechanism behind the improvement methods mainly includes two aspects, weakening Mg-H bond and compensating heat of reaction. Proceed from this, the experimental methods and enthalpy data as well as calculated values of enthalpy changes were compared systematically. Elements such as Ti, Nb, V, etc., with a small electronegativity difference compared to Mg, can reduce the hydrogenation and dehydrogenation enthalpy changes by forming strong Metal-H or Metal-Mg bonds. In addition, this review concludes with an outlook on the remaining challenge issues and prospects.

To have a better understand on the change of microstructure via kinetics, the diffusion behavior of Mg alloys is of special interest to researchers. Meanwhile, diffusion coefficients of Mg based alloys can explain and represent their diffusion behavior well. The evolution of experimental and calculated methods for detecting and extracting diffusion coefficients was discussed briefly. The reasonable diffusion data, especially self-diffusion coefficients, impurity diffusion coefficients and inter-diffusion coefficients of Mg alloys, were reviewed in detail serving to design the Mg alloys with higher accuracy. Then the practical applications of diffusion coefficients of Mg alloys were summarized, including diffusional mobility establishing, precipitation simulation and mechanical properties prediction.

The long-period stacking ordered phases (LPSOs) in Mg−Ni−Y system have been attracting great interest as effective strengthening components because of their unique structural characteristics and deformation mechanism. However, the phase relationships in LPSOs are complicated and unclear, which restricts the design of advanced magnesium-based alloys. The aim of the present work is to experimentally determine the phase equilibria relationships focusing on LPSOs and establish the thermodynamic description for Mg−Ni−Y system. Four types of LPSOs, that is, 14H, 12R, 18R and 10H, are confirmed through equilibrated alloys and high-resolution transmission electron microscopy (HR-TEM). The formation enthalpies of LPSOs (14H, 12R, 18R and 10H) are calculated based on density functional theories (DFT) calculations. A new ternary compound, termed as τ phase, is observed for the first time which is likely to be the distorted structure of 12R as determined from the TEM image which shows a 12-layer closed packing plane distance of 3.252 nm and a shear angle of 83.2° between (0002) and (1010) planes. Based on the determined phase equilibria relationship, the Mg−Ni−Y system is assessed and a self-consistent description is obtained where the LPSOs are modeled as the stoichiometric compounds. The comparison between the calculation result and experimental data suggests the accuracy of the present thermodynamic database in the Mg-rich corner.