Point defect diffusion in α-Zr
Point defect diffusion in α-Zr
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DOI：
10.1016/0022-3115(88)90091-8
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发表时间：
1988-10
影响因子：
3.1
通讯作者：
G. M. Hood
中科院分区：
文献类型：
--
作者：
G. M. Hood
目前对 α-Zr 缺陷的综述涉及原子和空位扩散以及溶质对辐射损伤的影响。解决原子扩散问题的主要目的是试图揭示本征扩散的特征和系统。这是在一般背景下以及在与 α-Zr 更具体相关的问题和特征方面完成的。后者包括各向异性晶体结构、α-β (hcp-bcc) 转变带来的 α 相稳定性的有限温度区间以及 Zr 具有高残留杂质水平的趋势。需要强调的是，只有使用高纯度单晶材料才能获得可靠的、固有的扩散数据。空位扩散是根据辐照损伤的实验数据来考虑的。基于溶质与空位和自填隙原子（SIA）的相互作用讨论了溶质对辐照损伤的影响。对原子扩散数据的考虑表明，α-Zr 中的自扩散本质上是正常的，并且与异常行为相关的自扩散数据可能表示由外在机制主导的扩散：结构和杂质相关的缺陷在这里似乎都很重要。固有扩散特性（扩散系数 (D) 以及相关的活化能和指前因子）往往以非常简单的方式随原子尺寸变化，扩散通过间隙机制和替代机制发生。小原子主要通过间隙路径扩散，相关的 D 值可能比与替代溶质相关的 D 值高许多数量级。扩散各向异性的测量表明，平行于 c 轴的扩散通常比垂直于 c 轴的扩散更快：这对于快速扩散、类间隙溶质来说是众所周知的，但对于替代性溶质来说却不是众所周知的。 α-Zr 的空位迁移特性一直是个谜。辐射损伤恢复的电子显微镜和正电子湮没光谱（PAS）测量的实验数据很容易用异常容易的空位迁移来解释，但是似乎没有任何明显的理论支持这种现象作为内在过程。这提出了外在机制的可能性。此外，与数据相关的似乎有足够的模糊性，以允许根据空位迁移本质上正常的模型来解释它们。在一般背景下讨论了溶质对辐照损伤和恢复的影响，并考虑了 SIA 对小溶质原子的吸引力以及静电和键合强度方法方面的溶质-空位相互作用。特别关注 Sn 的作用，因为 PAS 测量表明，Zr 的辐射损伤和恢复可以通过添加该元素进行合金化而深刻改变。对这些结果的一些理解可以从缺陷与溶质原子簇结构的相互作用方面找到。研究结果为开发抗辐射损伤合金的通用方法奠定了基础。
The present review of defects in α-Zr is concerned with atomic and vacancy diffusion and with solute effects on radiation damage. The primary aim, in addressing atomic diffusion, is to try to expose the characteristics and systematics of intrinsic diffusion. This is done, both in a general context and in terms of problems and features more specifically associated with α-Zr. Among the latter are the anisotropic crystal structure, the limited temperature interval of α-phase stability, imposed by the α-β (hcp-bcc) transformation, and the tendency for Zr to have high residual impurity levels. It is emphasized that reliable, intrinsic, diffusion data can only be obtained through the use of high-purity single-crystal material. Vacancy diffusion is considered in terms of experimental data on irradiation damage. Solute effects on irradiation damage are discussed on the basis of the interactions of solutes with vacancies and self-interstitial atoms (SIA). A consideration of atomic diffusion data indicates that self-diffusion in α-Zr is intrinsically normal and that self-diffusion data associated with abnormal behaviour are probably expressive of diffusion dominated by extrinsic mechanisms: both structural and impurity-related defects appear to be important here. Intrinsic diffusion characteristics (diffusion coefficients (D) and associated activation energies and pre-exponential factors) tend to scale in a remarkably simple manner with atomic size, with diffusion taking place by both interstitial and substitutional mechanisms. Small atoms diffuse mainly by interstitial paths, with associated D values which may be many orders of magnitude higher than those associated with substitutional solutes. Measurements of diffusion anisotropy show that diffusion is generally faster parallel to the c-axis than perpendicular to it: this is well established for fast-diffusing, interstitial-like solutes but not well known for substitutional solutes. The vacancy migration characteristics of α-Zr present an ongoing enigma. Experimental data from electron microscopic and positron annihilation spectroscopic (PAS) measurements of irradiation damage recovery are readily interpreted in terms of abnormally facile vacancy migration, however there does not appear to be any evident theoretical support for such a phenomenon as an intrinsic process. This raises the possibility of an extrinsic mechanism. In addition, there seems to be sufficient ambiguity associated with the data to allow their interpretation in terms of a model wherein vacancy migration is inherently normal. Solute effects on irradiation damage and recovery are discussed in a general context with a consideration of the attraction of SIAs for small solute atoms and of solute-vacancy interactions in terms of electrostatic and bond-strength approaches. Specific attention is given to the role of Sn, since it is shown, from PAS measurements, that radiation damage and recovery in Zr can be profoundly altered by alloying additions of this element. Some understanding of these results can be found in terms of defect interactions with clustered configurations of solute atoms. The results suggest the basis of a general approach towards the development of irradiation-damage resistant alloys.