Huang J Y, Wu Y K, Ye H Q
Laboratory of Atomic Imaging of Solids, Chinese Academy of Sciences, Shenyang, People's Republic of China.
Microsc Res Tech. 1998 Jan 15;40(2):101-21. doi: 10.1002/(SICI)1097-0029(19980115)40:2<101::AID-JEMT3>3.0.CO;2-Y.
HREM and FEG TEM were emphasized and extensively used to follow the most subtle changes in the structure and composition of ball-milled Cu, Fe-Cu, and thermally decomposed Fe60Cu40. Some significant results are obtained and summarized as follows: HREM shows that the deformation of ball-milled copper proceeds mainly by twinning and shear bands (SBs) formation. The nano-grains formed during ball milling (BM) contain a high density of dislocations. The grain boundaries (GBs) of nanocrystalline (NC) Cu prepared by BM are ordered, curved, and strained, but disordering, lattice distortion, and nanovoids in local regions were frequently observed. Nanoscale composition analysis on mechanically alloyed Fe16Cu84 shows that the average Fe content in both the interior of grains and the GBs is close to the designed composition, which proves that a supersaturated solid solution has really formed. However, the Fe content is rather inhomogeneous between the larger and smaller grains, which infers the inhomogeneous mixing of Fe and Cu during mechanical alloying (MA). NC structure and the mechanical force-enhanced fast diffusion are the reasons of the formation of supersaturated solid solutions in immiscible systems with positive enthalpy of mixing. HREM observations carried out with the thermally decomposed Fe60Cu40 solid solution show that the Nishiyama (N-W) or Kurdyumov-Sachs (K-S) orientation relationships exist between alpha-Fe and Cu. Energy dispersive X-ray spectra (EDXS) results show that the Cu content in these alpha-Fe grains reaches as high as 9.5 at.% even after heating to 1,400 degrees C, which is even higher than the maximum solubility of Cu in gamma-Fe at 1,094 degrees C.
高分辨电子显微镜（HREM）和场发射枪透射电子显微镜（FEG TEM）被重点强调并广泛用于追踪球磨铜、铁铜以及热分解的Fe60Cu40在结构和成分上最细微的变化。获得了一些重要结果并总结如下：HREM显示球磨铜的变形主要通过孪晶和剪切带（SBs）的形成进行。球磨（BM）过程中形成的纳米晶粒包含高密度的位错。通过BM制备的纳米晶（NC）铜的晶界（GBs）是有序的、弯曲的且有应变，但在局部区域经常观察到无序化、晶格畸变和纳米空洞。对机械合金化的Fe16Cu84进行的纳米级成分分析表明，晶粒内部和晶界中的平均铁含量接近设计成分，这证明确实形成了过饱和固溶体。然而，较大晶粒和较小晶粒之间的铁含量相当不均匀，这推断出在机械合金化（MA）过程中铁和铜的混合不均匀。NC结构和机械力增强的快速扩散是在具有正混合焓的不混溶体系中形成过饱和固溶体的原因。对热分解的Fe60Cu40固溶体进行的HREM观察表明，α-Fe和Cu之间存在西山（N-W）或库尔久莫夫-萨克斯（K-S）取向关系。能量色散X射线光谱（EDXS）结果表明，即使加热到1400摄氏度，这些α-Fe晶粒中的铜含量仍高达9.5原子百分比，这甚至高于铜在1094摄氏度时在γ-Fe中的最大溶解度。
