Impactful amelioration on the thermodynamics and kinetics of the RE-Mg-Ni-based alloys by melt spinning-crystallization annealing

The incorporation of transition metal Ni and rare-earth elements La and Y into Mg-based alloys significantly enhances hydrogen storage performance through synergistic effects. To optimize storage capacity and glass-forming ability (GFA), a Mg₉₀La₂Y₂Ni₆ alloy was designed and synthesized via induction casting and melt spinning. The amorphous alloy was further subjected to crystallization annealing at 400 ℃ to obtain a crystallized alloy. Structural analyses (XRD, SEM, HRTEM) revealed that the cast alloy comprised Mg, Mg₂Ni, La₂Mg₁₇, and YNi₃ phases. Melt spinning produced amorphous–nanocrystalline composites, with the amorphous fraction increasing with spinning rate. The crystallized alloy exhibited a phase composition similar to the cast alloy, but with finer, uniformly dispersed precipitates that provided enhanced diffusion pathways. Hydrogen storage properties were evaluated by Sievert apparatus and DSC. The crystallized alloy demonstrated markedly improved hydrogen absorption/desorption kinetics compared with the cast alloy. Specifically, the desorption activation energy decreased from 67.84 kJ/mol (cast) to 58.56 kJ/mol (crystallized, 30 m/s spinning rate). In addition, the initial hydrogen desorption temperature was reduced from 323.5 ℃ to 288.2 ℃. Thermodynamic analysis further confirmed a decrease in desorption enthalpy, indicating reduced hydride stability. Overall, the melt spinning–crystallization annealing route effectively tailors the microstructure and thermodynamics of Mg-based alloys, leading to lower activation energy, reduced desorption temperature, and enhanced hydrogen storage performance.