为开发出具有高循环寿命和高储氢性能的新能源汽车用稀土镁基储氢合金,考察了铸态和退火态的铸锭/快淬（La_0.7Mg_0.3）Ni_x（x=2.0、2.5、3.0）储氢合金的微观结构、物相组成和储氢特性。结果表明,当x=2.5时快淬法储氢合金具有较好的吸放氢平台压力,PCT曲线中体现出完全脱氢特征,吸氢容量约为1.44%（质量分数）。经过850~950 ℃退火处理,铸锭法（La_0.7Mg_0.3）Ni_2.5储氢合金相较（La_0.7Mg_0.3）Ni_2.0储氢合金具有更高的吸放氢平台压和更宽的吸放氢平台,表明前者具有相对更好的吸放氢性能;不同退火温度下（La_0.7Mg_0.3）Ni_2.5储氢合金的吸放氢平台压较为接近,吸氢和放氢容量可达到1.6%（质量分数）。铸锭法和快淬法（La_0.7Mg_0.3）Ni_x储氢合金中的LaNi₅和（LaMg）Ni₃相会随着退火温度的升高而逐渐转变为（LaMg）₂Ni₇相;铸锭法和快淬法（La_0.7Mg_0.3）Ni_2.5储氢合金的表面粉末颗粒分别在退火温度为950 ℃和900 ℃时最为细小。

In order to develop rare earth magnesium based hydrogen storage alloys with high cycle life and high hydrogen storage performance for new energy vehicles,the microstructure,phase composition and hydrogen storage properties of the cast and annealed ingot/rapidly quenched（La_0.7Mg_0.3）Ni_x（x=2.0,2.5,3.0） hydrogen storage alloys were investigated.The results showed that when x=2.5,the hydrogen storage alloy prepared by rapid quenching had good hydrogen absorption and desorption plateau pressure,and the complete dehydrogenation characteristic was shown in the PCT curve,and the hydrogen absorption capacity was about 1.44%（mass fraction）.After annealing at 850~950 ℃,the hydrogen absorption and desorption plateau of（La_0.7Mg_0.3）Ni_2.5 hydrogen storage alloy prepared by ingot method was higher and wider than that of（La_0.7Mg_0.3）Ni_2.0 hydrogen storage alloy,which indicated that the former had relatively better hydrogen absorption and desorption performance;the hydrogen absorption and desorption plateau pressure of（La_0.7Mg_0.3）Ni_2.5 hydrogen storage alloy at different annealing temperatures was close.The hydrogen and dehydrogenation capacity could reach 1.6%（mass fraction）.The LaNi₅ and（LaMg）Ni₃ phases in （La_0.7Mg_0.3）Ni_x hydrogen storage alloys by ingot casting and rapid quenching would gradually transform into（LaMg）₂Ni₇ phase with the increase of annealing temperature.The surface powder particles of （La_0.7Mg_0.3）Ni_2.5 hydrogen storage alloys prepared by ingot casting and rapid quenching were minimum at 950 ℃ and 900 ℃,respectively.