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Construction of Dislocation Structure Diagrams for Life Assessment of Materials

用于材料寿命评估的位错结构图的构建

基本信息

批准号：
13450284
负责人：
KATO Masaharu
金额：
$ 9.47万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

Strain-controlled cyclic deformation tests for pure Cu, Cu alloys, A1 and A1 alloys (mostly single crystals) were conducted. Although the crystal structure of these metals and alloys are all fcc, the fatigue behavior was quite different. For example, pure Cu showed cyclic hardening to saturation, whereas pure Al showed hardening followed by distinct softening. Observation of dislocation microstructure has revealed that the PSB ladder structure develops in Cu and it is absent in Al. Through extensive investigation, it has been found that the differences in both the fatigue behavior and microstructure can be explained by the relative feasibility of cross slip that is determined by the magnitude of stacking fault energy. Furthermore, from experiments using a Cu-Fe alloy with dispersed small Fe precipitate particles in Cu, it has been found that the Fe particles are effective in preventing the development of fatigue dislocation structure. With this knowledge, dislocation structure diagrams that indicate fatigue dislocation structure as a function of size and distribution of second-phase particles were successfully constructed.Dislocation structures developed during fatigue tests are found to be much more stable (both thermally and mechanically) compared with those developed after cold rolling. Owing to the to-and-fro motion during cyclic deformation, dislocations arrange themselves into an energetically stable configuration resulting in the formation of characteristic fatigue microstructures that eventually lead to fatigue failure.In conclusion, we could obtain various new results and findings, most of which are very valuable for life assessment of structural materials.

对纯铜、铜合金、A1和A1合金（主要是单晶）进行了应变控制循环变形试验。虽然这些金属和合金的晶体结构都是面心立方结构，但它们的疲劳行为却有很大的不同。例如，纯铜表现出循环硬化饱和，而纯铝表现出硬化，然后明显软化。位错微观结构的观察表明，PSB梯形结构的发展在铜和它是缺席的铝。通过广泛的调查，它已被发现，在疲劳行为和微观结构的差异可以解释的交叉滑移，这是由层错能的大小决定的相对可行性。此外，从使用在Cu中分散有小Fe沉淀物颗粒的Cu-Fe合金的实验中，已经发现Fe颗粒在防止疲劳位错结构的发展方面是有效的。在此基础上，成功地绘制了疲劳位错结构与第二相粒子尺寸和分布的关系图，发现疲劳试验中产生的位错结构比冷轧后产生的位错结构稳定得多（热稳定性和机械稳定性）。由于循环变形过程中位错的往复运动，位错排列成能量稳定的结构，从而形成特征疲劳组织，最终导致疲劳失效，得到了许多新的结果和发现，其中大部分对结构材料的寿命评估是非常有价值的。