Dual-Stage Heat Treatment for Enhanced Hydrogen Storage Properties of Mg−Ni−Y Alloys

en Mg−Ni−Y alloy is considered to be one of the most promising hydrogen storage materials, but its high dehydrogenation energy barrier hinders its practical application. A dual-stage heat treatment (490°C × 4 h + 550°C × 4 h) is applied to optimize the microstructure and hydrogen storage performance of a vacuum-melted Mg 94 Ni 3 Y 3 alloy. This process induces a two-level phase transformation of the long-period stacking ordered (LPSO) structure (18R + 14H→14H→18R), facilitating Ni/Y atom pre-distribution via stacking fault recombination at 490°C and promoting a eutectic-like reaction at 550°C. As a result, a large-scale eutectic-like structure composed of finely dispersed and uniformly interwoven Mg 2 Ni and LPSO phases is formed, characterized by a high density of phase boundaries. The optimization of the microstructure directly leads to the enhancement of hydrogen storage performance, as evidenced by a reduction in dehydrogenation activation energy from 139.7 to 113.5 kJ mol −1 and a decrease in enthalpy change from 85.8 to 71.7 kJ mol −1 . This work demonstrates a convenient microstructure regulation strategy, which is expected to advance Mg−Ni−Y alloys toward industrial applications. 摘要 zh Mg−Ni−Y 合金因其优异的储氢潜力而备受关注,但较高的脱氢能垒仍制约其工程化应用。针对真空熔炼的Mg 94 Ni 3 Y 3 合金,本研究采用双阶段热处理工艺(490°C×4 h+550°C×4 h)调控其显微组织与储氢性能。结果表明,该工艺诱导长周期堆垛有序(LPSO)结构经历两级相变过程(18R+14H→14H→18R):在490°C通过层错重组实现Ni/Y原子的预分布,在550°C进一步促进类共晶反应的发生。由此形成的大尺度类共晶组织由细小弥散且均匀交织的Mg 2 Ni相与 LPSO 相构成,具有高密度相界特征。显微组织的显著优化有效降低了脱氢活化能(由139.7降至113.5 kJ mol −1 )和焓变(由85.8降至71.7 kJ mol −1 ),从而提升了储氢动力学性能。本工作提出了一种简便高效的组织调控策略,为Mg−Ni−Y合金的工程化应用提供了新思路。