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Grain boundaries of nanophase materials.

机译：纳米相材料的晶界。

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摘要

Several iron alloys with nanometer-scale grain sizes were prepared by mechanical attrition in a high energy ball mill. Mossbauer spectrometry was used to measure the internal hyperfine magnetic fields. X-ray diffractometry (XRD) and transmission electron microscopy (TEM) were used to measure the grain size. The proposed structures of nanophase materials consist of two components of comparable volume fractions: a crystalline component and an interfacial component. By correlating features in the Mossbauer spectra to the structural results of XRD and TEM, we identified the hyperfine magnetic fields of {dollar}sp{lcub}57{rcub}{dollar}Fe atoms at grain boundaries. Once identified, the fractions of {dollar}sp{lcub}57{rcub}{dollar}Fe atoms at grain boundaries were determined by the intensities of their magnetic signatures seen in Mossbauer spectra. With data on the fraction of {dollar}sp{lcub}57{rcub}{dollar}Fe atoms at grain boundaries versus grain size, a model of the microstructure can be used to obtain the average width of the grain boundaries. Data from the model were obtained by Monte Carlo simulations. The average grain boundary widths of the fcc alloys Fe-Mn and Ni-Fe are approximately 0.5 nm, but the average widths of grain boundaries in the bcc alloys Cr-Fe and Fe-Ti are larger, approximately 1 nm.; The Debye temperature is a physical parameter of the vibrational spectrum of the solid. The difference in the Debye temperatures between the grain boundaries and the crystalline regions was found. The Debye temperature of the crystallites in nanophase Cr-Fe is 470 K, which is larger than that of grain boundary component, 370 K.
机译：通过在高能球磨机中进行机械磨蚀，制备了几种具有纳米级晶粒尺寸的铁合金。莫斯鲍尔光谱法用于测量内部超精细磁场。 X射线衍射（XRD）和透射电子显微镜（TEM）用于测量晶粒尺寸。所提出的纳米相材料的结构由体积分数相当的两个组分组成：结晶组分和界面组分。通过将Mossbauer光谱中的特征与XRD和TEM的结构结果相关联，我们确定了晶界处{dol} sp {lcub} 57 {rcub} {dollar} Fe原子的超细磁场。一旦确定，晶界处的{sp} lc {lcub} 57 {rcub} {dol}} Fe原子的分数由在莫斯鲍尔光谱中看到的磁签名强度确定。利用关于晶界处的{sp} lc {lcub} 57 {rcub} {dollar} Fe原子分数与晶粒尺寸的数据，可以使用微观结构模型来获得晶界的平均宽度。该模型的数据通过蒙特卡洛模拟获得。 fcc合金Fe-Mn和Ni-Fe的平均晶界宽度约为0.5nm，而bcc合金Cr-Fe和Fe-Ti的平均晶界宽度较大，约为1nm。德拜温度是固体振动光谱的物理参数。发现了晶界和结晶区之间的德拜温度差异。纳米相Cr-Fe中微晶的德拜温度为470 K，高于晶界成分的370 K.

著录项

  • 作者

    Ouyang, Hao.;

  • 作者单位

    California Institute of Technology.;

  • 授予单位 California Institute of Technology.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 1993
  • 页码 161 p.
  • 总页数 161
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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