The effect of substitutional elements (Al, Co) in LaNi4.5M0.5 on the lattice defect formation in the initial hydrogenation and dehydrogenation
The effect of substitutional elements (Al, Co) in LaNi4.5M0.5 on the lattice defect formation in the initial hydrogenation and dehydrogenation
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DOI：
10.1016/j.jallcom.2008.05.044
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发表时间：
2009-04
影响因子：
6.2
通讯作者：
K. Sakaki;E. Akiba;M. Mizuno;H. Araki;Y. Shirai
中科院分区：
文献类型：
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作者：
K. Sakaki;E. Akiba;M. Mizuno;H. Araki;Y. Shirai
用正电子寿命技术观察了LaNi_（4.5）M_（0.5）（M=Al，Co，Ni）中由初始氢化和脱氢形成的空位和位错。这些工艺引入的空位浓度分别为0.25，0.13和0.01at.% LaNi_（4.5）Co_（0.5）和LaNi_（4.5）Al_（0.5）。与LaNi5和LaNi4.5Co0.5相比，Al替代LaNi5能显著抑制空位的形成。在LaNi 4.5Al 0.5合金中，与LaNi 5.5合金相比，Co的加入提高了合金的硬度和粉化程度，即增加了微裂纹的形成，而Co的加入对粉化程度、硬度和空位的形成影响不大。这些结果表明，由于LaNi 4.5Al 0.5合金中晶格缺陷的形成能较高，Al替代使微裂纹的形成比晶格缺陷的形成更加活跃，从而释放氢化物形成所产生的应变能，尽管在我们研究的所有合金中仍然观察到微裂纹和晶格缺陷的形成。
The formation of the vacancy and dislocation by the initial hydrogenation and dehydrogenation in LaNi4.5M0.5(M=Al, Co, and Ni) was observed by means of the positron lifetime technique. The concentrations of vacancy introduced by these processes were 0.25, 0.13 and 0.01at.% for LaNi5, LaNi4.5Co0.5and LaNi4.5Al0.5, respectively. Al substitution into LaNi5significantly prevented from vacancy formation, compared with LaNi5and LaNi4.5Co0.5. In LaNi4.5Al0.5, the increase of the hardness and the enhancement of the pulverization, i.e. enhancement of the formation of micro cracks compared with LaNi5were observed while the Co substitution had little effect on pulverization and hardness as well as vacancy formation. These results show that the formation of micro cracks became more active process by Al substitution than the formation of the lattice defects to release the strain energy generated by the hydride formation because of the higher formation energy of the lattice defects in LaNi4.5Al0.5, although both the formation of micro cracks and lattice defects were still observed in all alloys we studied.