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Microstructure and magnetic behavior studies of processing-controlled and composition-modified Fe-Ni and Mn-Al alloys.

机译：加工控制和成分改性的Fe-Ni和Mn-Al合金的微观结构和磁行为研究。

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摘要

L10-type (Space group P4/mmm) magnetic compounds, including FeNi and MnAl, possess promising technical magnetic properties of both high magnetization and large magnetocrystalline anisotropy energy, and thus offer potential in replacing rare earth permanent magnets in some applications.;In equiatomic Fe-Ni, the disorder-order transformation from fcc structure to the L10 structure is a diffusional transformation, but is inhibited by the low ordering temperature. The transformation could be enhanced through the creation of vacancies. Thus, mechanical alloying was employed to generate more open-volume defects. A decrease in grain size and concomitant increase in grain boundary area resulted from the mechanical alloying, while an initial increase in internal strain (manifested through an increase in dislocation density) was followed by a subsequent decrease with further alloying. However, a decrease in the net defect concentration was determined by Doppler broadening positron annihilation spectroscopy, as open volume defects utilized dislocations and grain boundaries as sinks.;An alloy, Fe32Ni52Zr3B13, formed an amorphous structure after rapid solidification, with a higher defect concentration than crystalline materials. Mechanical milling was utilized in an attempt to generate even more defects. However, it was observed that Fe32Ni52Zr3B13 underwent crystallization during the milling process, which appears to be related to enhanced vacancy-type defect concentrations allowing growth of pre-existing Fe(Ni) nuclei. The milling and enhanced vacancy concentration also de-stabilizes the glass, leading to decreased crystallization temperatures, and ultimately leading to complete crystallization.;In Mn-Al, the L10 structure forms from the parent hcp phase. However, this phase is slightly hyperstoichiometric relative to Mn, and the excess Mn occupies Al sites and couples antiparallel to the other Mn atoms. In this study, the Zr substituted preferentially for the Mn atoms in the Al layer, resulting in an increase in saturation magnetization, from 115 emu/g in the alloys without Zr to 128 emu/g in Mn53Al43C 3Zr1. To further improve the coercivity in Mn53Al 43C3Zr1, microstructure modification was achieved through the addition of excessive C and through surfactant-assisted mechanical milling. Enhancement in coercivity was accomplished through the microstructure modification, however, the loss of saturation magnetization was observed due to the formation of other equilibrium phases, including epsilon, beta-Mn and ZrO.
机译：包括FeNi和MnAl在内的L10型（空间群P4 / mmm）磁性化合物具有高磁化和大磁晶各向异性能的有希望的技术磁性能，因此在某些应用中具有替代稀土永磁体的潜力。 Fe-Ni，从fcc结构到L10结构的无序转变是扩散转变，但受低有序温度抑制。可以通过创建空缺来促进这种转变。因此，采用机械合金化来产生更多的开孔缺陷。机械合金化导致晶粒尺寸的减小和晶界面积的增加，而内部应变的初始增加（通过位错密度的增加而表现出），随后随着进一步合金化而减小。然而，由于开体积缺陷利用位错和晶界作为沉陷，因此通过多普勒展宽正电子an没光谱法确定了净缺陷浓度的降低；合金Fe32Ni52Zr3B13在快速凝固后形成非晶态结构，缺陷浓度高于结晶物质。利用机械研磨试图产生更多的缺陷。然而，据观察，Fe32Ni52Zr3B13在研磨过程中经历了结晶，这似乎与空位型缺陷浓度的增加有关，允许先前存在的Fe（Ni）核的生长。研磨和增加的空位浓度还会使玻璃不稳定，从而导致结晶温度降低，并最终导致完全结晶。在Mn-Al中，L10结构由母体hcp相形成。但是，该相相对于Mn而言是化学计量过量的，并且过量的Mn占据Al位点，并且与其他Mn原子反平行偶联。在这项研究中，Zr优先取代了Al层中的Mn原子，导致饱和磁化强度从无Zr的合金中的115 emu / g增加到Mn53Al43C 3Zr1中的128 emu / g。为了进一步提高Mn53Al 43C3Zr1的矫顽力，通过添加过量的C和通过表面活性剂辅助的机械研磨实现了微观结构的改性。矫顽力的提高是通过微观结构的改变实现的，但是，由于其他平衡相的形成，包括ε，β-Mn和ZrO的形成，饱和磁化强度的损失也得以观察到。

著录项

  • 作者

    Geng, Yunlong.;

  • 作者单位

    The University of Nebraska - Lincoln.;

  • 授予单位 The University of Nebraska - Lincoln.;
  • 学科 Materials science.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 167 p.
  • 总页数 167
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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