深冷处理对纯铜低周疲劳性能的影响
关键词 铜 等径角挤压 超细晶组织 深冷处理 疲劳寿命
毕业论文设计说明书外文摘要
Title The effect of cryogenic treatment on the low cycle fatigue properties of pure copper
Abstract
Equal Channel Angular Pressing（ECAP）is a unique method for preparing high performance materials which could prepare bulk ultrafine grained materials successfully by strong pure shear deformation. This experiment has had the deep cryogenic treating on pure copper with four passages of extrusion , and the strain controlled tension depression experiment has been carried out to learn the relationship between the deep cryogenic treating and the fatigue life of the ultrafine grained pure copper .The morphology of the surface of different amplitude was observed by optical microscope. The microstructure of the samples was observed and analyzed by electron microscope. The grain size distribution and the orientation difference distribution were characterized by EBSD technique. The relationship called Coffin-Manson relationship between plastic strain amplitude and fatigue life is to be find out, basing on which the effect of cryogenic treatment on the fatigue life of zhe ultrafine grained pure copper.
Keywords copper Equal Channel Angular Pressing ultrafine grained materials deep cryogenic treating fatigue life
目 次
1 引言 1
2 实验材料及方法 5
2.1 实验材料 5
2.2 深冷处理 5
2.3 低周疲劳实验 5
2.4 EBSD实验 5
3 实验结果及分析 6
3.1 静态拉伸性能 6
3.2 低周疲劳性能 6
3.3 EBSD分析 11
结论 15
致谢 16
参考文献17
1 引言
因为超细晶材料具备很多不同寻常的物理性质、化学性质和力学性能，材料科学方面的学者对超细晶材料表现出了强烈的兴趣。近些年，采用塑性变形方法获得超细晶材料的新工艺——等径角挤压受到了格外关注。经过等径角挤压（ECAP）处理的超细晶(UFG)铜在应力控制测试下显示出疲劳寿命的提高[1]，相比于对应的粗粒，在持续塑性应变控制测试中出现了疲劳寿命恶化和循环软化[2,3]。
近年来，运用ECAP技术制备超细晶材料已成为材料领域的一个研究热点[4-7]。采用该工艺经过多道次挤压能够在不变动材料胚料基本尺寸的情况下取得很高的剪切变形量，从而可取得亚微米级甚至纳米级的晶粒细化的效果，它仅改变了材料的显微组织而没有改变其成分，经济有效地提高了材料的力学性能。
冰冷处理是一种经过将被处理工件放置于特定可控的低温环境中，使材料的微观组织结构发生变化，从而能够提高、改善材料性能的方法。工业中通常把材料经过普通的热处理后进一步冷却到摄氏零度以下某一温度（通常为0～-130℃）的处理方法称为普通冷处理；而把低于-130℃以下（通常为-130℃～-196℃）的冷处理叫做深冷处理。
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