• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Combined reactions thermomechanical processing applied to ferromagnetic iron-palladium binary alloys.
【24h】

Combined reactions thermomechanical processing applied to ferromagnetic iron-palladium binary alloys.

机译：组合反应热机械加工应用于铁磁铁钯二元合金。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The aim of this thesis was to use a combination of thermomechanical processing and heat treatment, including magnetic field annealing, to tailor ultra-fine microstructures with enhanced properties in ferromagnetic alloys. The combined reactions strategy involves the use of thermomechanical processing to induce two or more solid-state reactions to occur concomitantly, synergistically and / or sequentially during microstructural development, e.g. severe plastic deformation followed by recrystallization in tandem with precipitation, ordering and / or decomposition. The specific thrust is aimed at producing exchange-coupled nanocomposite structures in off-stoichiometric Fe-Pd alloys, which might be expected to form two-phase mixtures of magnetically soft ferrite (alpha) and the magnetically hard L10 intermetallic phase. The severe plastic deformation of the parent phase serves to enhance diffusion kinetics in addition to catalyzing novel reaction paths and microstructural development as the system relaxes toward equilibrium. Vibrating sample magnetometry (VSM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were performed to investigate the microstructure and the magnetic properties of combined reactions transformed hypo-stoichiometric iron-palladium. Two distinct microstructures were observed to develop in these alloys, resulting from two different modes of solid-state transformation. Conventional aging of the solutionized alloys resulted in eutectoid decomposition whereby the ferrite and L10 phases precipitate a cellular product on a 100nm length scale that coarsens as aging progresses. In contrast, aging the deformed alloys produces a nanoscale lamellar composite structure consisting of alternate L10 and metastable FCC phases, on a scale of 10nm. The finer scale product appears to derive from pseudospinodal decomposition, while ferrite is simultaneously observed to precipitate heterogeneously on grain boundaries. The plastic deformation imparts crystallographic texture to the alloys that is substantially retained in the final microstructure, suggesting that the mechanism of transformation preserves the orientation of the parent grains. The soft ferrite is exchange coupled with the aligned L10 phase at length scales exceeding the critical length scale predicted by existing theory. Peak properties were obtained when Fe-35at%Pd was deformed 97% and aged at 425°C for 20 hours resulting in a coercivity of 1kOe and an energy product equal to 2.9MG*Oe. These results have been quantitatively rationalized in terms of a superposition of domain wall pinning by particles and grain boundaries. Nucleation and growth rates of ferrite and L10 FePd increased when the alloys were aged within a 9 Tesla magnetic field.
机译：本文的目的是结合使用热机械加工和热处理（包括磁场退火）来定制具有增强性能的铁磁合金中的超细微结构。组合反应策略涉及使用热机械加工来诱导两个或更多个固态反应，例如在微结构开发期间同时，协同和/或顺序地发生。严重的塑性变形，随后伴随沉淀，有序和/或分解的重结晶。特定推力的目的是在化学计量比为Fe-Pd的合金中产生交换耦合的纳米复合结构，可以预期形成磁性软的铁氧体（α）和磁性硬的L10金属间相的两相混合物。当体系趋于平衡时，母相的严重塑性变形除了催化新的反应路径和微观结构发展外，还有助于增强扩散动力学。进行了振动样品磁力分析（VSM），X射线衍射（XRD），扫描电子显微镜（SEM）和透射电子显微镜（TEM），以研究低化学计量的铁钯组合反应的微观结构和磁性。观察到由于两种不同的固态转变模式，在这些合金中形成了两种不同的微观结构。固溶合金的常规时效导致共析分解，铁素体和L10相在100nm长的尺度上沉淀出蜂窝状产物，随着时效的进行而粗化。相反，时效处理变形后的合金会产生纳米级的层状复合结构，该结构由交替的L10相和亚稳态FCC相组成，尺度为10nm。较细的产物似乎来自拟螺状分解，而同时观察到铁素体在晶界上异质沉淀。塑性变形使合金具有晶体结构，而该结构基本上保留在最终的微观结构中，这表明相变机理保留了母体晶粒的取向。软铁氧体与对准的L10相交换耦合，其长度尺度超过了现有理论所预测的临界长度尺度。当Fe-35at％Pd变形97％并在425°C时效20小时时，可获得峰特性，其矫顽力为1kOe，能量积为2.9MG * Oe。这些结果已根据颗粒和晶粒边界对畴壁钉扎的叠加进行了定量合理化。当合金在9 Tesla磁场中时效时，铁素体和L10 FePd的形核和生长速率增加。

著录项

  • 作者

    Cantando, Elizabeth Dawn.;

  • 作者单位

    University of Virginia.;

  • 授予单位 University of Virginia.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 149 p.
  • 总页数 149
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号