退火时间对LaMgNi3.9Mn0.2合金的结构与气态吸放氢性能的影响

Effect of Annealing Time on Structure and Gaseous Hydrogen Absorption and Desorption Properties of LaMgNi3.9Mn0.2 Alloy

为了研究退火时间对LaMgNi3.9Mn0.2合金的结构和气态吸放氢性能的影响,采用XRD和SEM手段测试了合金的物相和微观结构,半自动Siever′s法测试了合金的吸放氢动力学曲线。实验结果表明,随着退火时间增加,合金中LaMg(NiMn)4主相含量降低,(La,Mg)(NiMn)5相含量增加。铸态及退火合金表面均由不同尺寸的柱状晶组成,具有明显的组织遗传效应;随着退火时间增加,合金柱状晶区域中La、Mg、Ni的含量差值都降低,元素分布更均匀,15 h与20 h退火合金的柱状晶晶间区域中Mn元素消失。铸态和退火合金第一次吸氢后达到相应的最大吸氢量,故退火时间对合金的活化性能无影响,但对合金的最大吸氢量、饱和吸放氢量具有明显影响。随着退火时间增加,合金的最大吸氢量、饱和吸放氢量降低,但合金的吸放氢饱和率先增加后降低,15 h退火合金的吸放氢饱和率相对较高。

In order to study the effect of annealing time on structure and gaseous hydrogen absorption and desorption properties of LaMgNi3.9Mn0.2 alloy,the phase and microstructure of the alloy were tested by XRD and SEM,and the hydrogen absorption and desorption kinetics plot was tested by semi-automatic Siever′s method.The experimental results show that with the increase of annealing time,the content of main phase LaMg(NiMn)4 decreases,while the content of(La,Mg)(NiMn)5 increases.The surface of as-cast and annealed alloys is mainly composed of columnar crystals with different sizes,which has obvious structural heredity.With the increase of annealing time,the content differences of La,Mg and Ni in the columnar crystal region of the alloy decrease,which makes the element distribution more uniform.Mn element disappears in the columnar crystal intergranular region of the alloy annealed for 15 h and 20 h.After the first hydrogen absorption of as-cast and annealed alloys,the corresponding maximum hydrogen absorption is reached.Therefore,the annealing time has no effect on the activation performance of the alloy,but has a significant effect on the maximum hydrogen absorption and the saturated hydrogen absorption and desorption of the alloy.With the increase of annealing time,the maximum hydrogen absorption and saturated hydrogen absorption and desorption of the alloy decrease,but the hydrogen absorption and desorption saturation increases firstly and then decreases,and that of the alloy annealed for 15 h is relatively high.