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Fatigue Tests of Copper Single Crystals with Martensitically Transformable Small Dispersed Iron Particles

马氏体相变小弥散铁颗粒铜单晶的疲劳试验

基本信息

批准号：
03650571
负责人：
KATO Masaharu
金额：
$ 1.22万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

It is known that proper heat treatment can produce coherent gamma-iron or incoherent alpha-iron fine precipitate particles in a copper matrix. It is also known that plastic deformation induces gamma*alpha martensitic transformation in the coherent gamma-iron particles. The purpose of this research is to examine the effects of these particles on the fatigue behavior and on the development of fatigue dislocation structure using Cu-Fe alloy single crystals.When Cu-Fe alloy specimens were cyclically deformed under plastic strain control. cyclic hardening was observed regardless of the type (coherent or incoherent) of the particles. The lack of cyclic softening is attributed to the fact that initially coherent gamma-iron particles transform martensitically into incoherent alpha-iron in the early stage of the cyclic deformation. In any specimen, the so-called plateau region was found to exist in the cyclic stressstrain curves. However, different from copper single crystals where the characteristic ladder dislocation structure is observed in the plateau region, dislocations were more irregular and tangled in the Cu-Fe alloy single crystals. This is indicative of the strong effect of dispersed particles on preventing the dislocation rearrangement to form characteristic fatigue dislocation structure.It is concluded from this study that unlike usual coherent dispersed particles, the coherent gamma-iron particles are very effective in improving fatigue resistance of copper because of their transformability.

已知适当的热处理可以在铜基体中产生相干的γ-铁或不相干的α-铁细沉淀颗粒。还已知的是，塑性变形在相干γ-铁颗粒中诱导γ * α马氏体转变。本研究的目的是利用Cu-Fe合金单晶，在塑性应变控制下循环变形，研究这些颗粒对Cu-Fe合金疲劳行为和疲劳位错结构发展的影响。观察到循环硬化，而与颗粒的类型（相干或非相干）无关。循环软化的缺乏归因于这样一个事实，即在循环变形的早期阶段，最初共格的γ-铁颗粒马氏体转变为非共格的α-铁。在任何试样中，所谓的平台区被发现存在于循环应力-应变曲线。然而，与铜单晶中观察到的特征性梯形位错结构的平台区不同，位错在Cu-Fe合金单晶中更不规则且缠结。这表明弥散颗粒对阻止位错重排形成特征疲劳位错结构有很强的作用，由此得出结论，与通常的共格弥散颗粒不同，共格γ-Fe颗粒由于其可变形性而对提高铜的疲劳抗力非常有效。