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Experimental and theoretical approach for mobile defect clusters introduced under heavy ion irradiations

重离子辐照下引入的移动缺陷簇的实验和理论方法

基本信息

批准号：
18560801
负责人：
ABE Hiroaki
金额：
$ 2.31万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

Irradiation with ions and/or neutrons deteriorates properties of materials introducing lattice defects. One of the typical defects is displacement cascades in which "spontaneously melted" volumes are generated leaving point defects. The recent study on the displacement cascades revealed that bundles of interstitial atoms (crowdion bundles) are formed in the cascade process and may travel in the matrix with low activation energy. The defects are presumed to accumulate at defects such as grain boundary, precipitates, dislocations etc, inducing decorations and diffusion or retarding dislocation motion. In this work, the effects of the crowdion bundles on the microstructure evolution are investigated.This work consists of (1) in-situ observations in a transmission electron microscope (TEM) interfaced with an ion accelerator and (2) cross section TEM in ion-irradiated materials.(1) Electron transparency of fully-annealed copper and gold were prepared and set in the TEM for ion irradiations with heavy ions at the temperature from 670 to 870 K. Mobile defects associated with displacement cascades were observed. The typical traveling distance ranges 20 to 140 nm, however the upper limit was due to the limitation of observation area. The lifetime and the direction of mobility were systematically analyzed, and the formation of crowdion-type interstitial bundle was concluded.(2) Coherent-to-incoherent transition of strain contrast of coherent precipitates in dilute Cu-Co system was observed upon ion irradiation. The effect propagated over the range of ions, strongly indicating diffusion of crowdion bundles which is concluded by fluence, flux and temperature dependences.The above results were summarized as two research papers and an international conference in the fiscal year of 2007.

用离子和/或中子辐照会使引入晶格缺陷的材料的性质劣化。其中一个典型的缺陷是位移级联，其中产生“自发熔化”的体积，留下点缺陷。最近对位移级联的研究表明，在级联过程中形成了间隙原子束（crowdion束），并且可能以低活化能在基质中移动。这些缺陷被认为是在诸如晶界、沉淀物、位错等缺陷处积累，从而引起装饰和扩散或阻碍位错运动。本文研究了离子束对微结构演化的影响，包括（1）在离子加速器上的透射电子显微镜（TEM）原位观察和（2）在离子辐照材料中的横截面TEM观察。(1)在670 ~ 870 K温度范围内，制备了完全退火的铜和金的电子透过性，并将其置于重离子辐照的透射电镜中。观察到与位移级联相关的移动的缺陷。典型的行进距离范围为20至140 nm，但上限是由于观察区域的限制。系统地分析了其寿命和迁移方向，得出了crowdion型间隙束的形成。(2)在离子辐照下，观察到了Cu-Co系共格沉淀应变衬度的相干-非相干转变。该效应在离子范围内传播，强烈表明crowdion束的扩散，这是由注量，通量和温度dependences.The上述结果总结为两篇研究论文和2007财政年度的国际会议。