Defect generation and analysis in mechanically alloyed stoichiometric Fe-Ni alloys
Defect generation and analysis in mechanically alloyed stoichiometric Fe-Ni alloys
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DOI：
10.1016/j.jallcom.2015.02.038
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发表时间：
2015-06-05
影响因子：
6.2
通讯作者：
Shield, Jeffrey E.
中科院分区：
文献类型：
--
作者：
Geng, Yunlong;Ablekim, Tursunjan;Shield, Jeffrey E.
具有化学有序L1(0)四方结构的FeNi是下一代无稀土永磁体的一种有前途的材料。由于在320℃的临界化学有序/无序温度以下，铁和镍原子的迁移率极低，常规的冶金方法无法诱导其形成。通过产生过量的空位可以提高扩散速率。采用高能机械合金化方法制备了纳米晶Fe - 50at.% Ni合金。高能机械球磨有望改变缺陷特征，这些特征可用于研究机械合金化对缺陷浓度的影响。X射线衍射表明，在整个球磨过程中，铁和镍粉末形成了面心立方固溶体。威廉姆森 - 霍尔方程和谢乐方程表明，合金化过程中晶粒尺寸减小。内应变最初增加，进而位错增加，随着进一步合金化应变随后降低，这是由于机械变形产生位错以及在不断增加的晶界处位错湮灭的综合作用。正电子湮没多普勒展宽谱（DB - PAS）表明，随着球磨时间增加，开放体积缺陷的总数减少。最后，对于机械合金化的FeNi相，相对磁导率的变化由位错的钉扎效应来解释。（C）2015爱思唯尔有限公司保留所有权利。
FeNi, with the chemically-ordered L1(0) tetragonal structure, is a promising material for next-generation rare-earth-free permanent magnets. Due to the extremely low atomic Fe and Ni mobility below the critical chemical order/disorder temperature of 320 degrees C, no conventional metallurgical methods are able to induce its formation. Diffusion rates could be enhanced with the creation of excessive vacancies. High-energy mechanical alloying was employed to produce a nanocrystalline Fe-50 at.% Ni alloy. The high energy mechanical milling is expected to change the defect characteristics that would be used to study the effect that mechanical alloying has on the defect concentrations. X-ray diffraction revealed that over the entirety of the milling period, the Fe and Ni powders formed an fcc solid solution. The WilliamsonHall equation and Scherrer equation revealed that reductions in grain sizes were caused during alloying. The initial increase in internal strain, and by extension dislocations, was followed by a decrease in strain with further alloying, which was due to the combination effect of creation of dislocation from mechanical deformation and annihilation of dislocations at increasing grain boundaries. Doppler broadening positron annihilation spectroscopy ( DB-PAS) showed that the overall number of open-volume defects decreased with increased milling time. Finally, changes of relative permeability, for the mechanically alloyed FeNi phase, were explained by the pinning effect of dislocations. (C) 2015 Elsevier B.V. All rights reserved.