Research and development of exchange spring magnet by means of micro-alloying technique

本研究的主要目的是揭示少量添加剂在交换弹簧磁体中的作用。少量的添加剂有时会在结晶过程中大大减小晶体的晶粒尺寸。本文主要利用荧光XAFS技术研究了小添加剂在非晶态结晶和加氢过程中局部结构的变化。结果表明，在晶化初期，Fe_<73>Ga_4Nb_3Si_<11>B_9中的Ga向析出的α - fe界面移动，随着晶化的进行，Ga被纳入α - fe中。我们还研究了Nd_<13.6>Fe_<68.2>Co_<10.8>Ga_<1.0>Zr_<0.1>B_<6.9>加氢前后Ga和Zr的局部结构变化。加氢前Ga包含在Nd_2Fe_<14>B中，加氢后Ga进入α - fe。另一方面，Zr与氢选择性成键，氢化后生成ZrH_2。目前尚不清楚Ga和Zr在HDDR中的这种行为与晶体记忆效应之间的关系。这需要进一步的调查来揭示。

The main purpose of this study is to reveal the roles of small amount of additives in the exchange spring magnets. Small additives sometimes drastically reduce grain size of crystallites in the crystallization from amorphous states. Here we have mainly investigated the changes of local structures of small additives by fluorescence XAFS during crystallization from amorphous states and during hydrogenation. It has been found that Ga in Fe_<73>Ga_4Nb_3Si_<11>B_9 moves toward interface of precipitated alpha-Fe at an early stage of crystallization, and then included into alpha-Fe with the crystallization being proceeded. We also studied the local structure changes of Ga and Zr in Nd_<13.6>Fe_<68.2>Co_<10.8>Ga_<1.0>Zr_<0.1>B_<6.9> before and after hydrogenation. Before hydrogenation Ga is included in Nd_2Fe_<14>B and after hydrogenation it moves into alpha-Fe. On the other hand Zr makes selective bonding to hydrogen and forms ZrH_2 after the hydrogenation.At the present stage how such behaviors of Ga and Zr in HDDR are related with the crystalline memory effects are not yet clear. Further investigations are needed to reveal it.