纳米结构Al-0.3%Cu合金的力学稳定性和热稳定性研究

发布时间：2021-04-27 05:34

　　纳米结构金属因具有较传统粗晶材料高得多的强度,具有较好的工程应用潜力。但其加工硬化能力低、塑性差,而且由于高密度的晶界和晶体缺陷所导致的高储存能而使其微观结构的热稳定性差,这些问题严重制约了其实际应用。探讨提高纳米结构金属力学稳定性和热稳定性的途径,具有重要意义。在本论文中,设计制备了一种纳米结构Al-0.3%Cu合金,该合金以超高纯铝（99.9996%）为基体,在基体中加入质量比为0.3%的高纯度Cu（99.99%）固溶元素。目的是利用固溶元素Cu稳定纳米结构Al-0.3%Cu合金的微观组织和塑性流变,以探寻一种优化纳米结构材料的微观组织结构和力学性能的新的材料设计方法。通过98%形变量的高应变冷轧变形获得了具有纳米结构的材料,用于研究其热稳定性和力学性能。通过对冷轧和不同工艺下热处理后材料的力学行为进行系统的测试,以及利用透射电镜（TEM）和电子背散射衍射（EBSD）等方法对材料的微观组织进行的系统表征,得到如下结论:①通过室温98%的冷轧变形,获得了平行于轧面而沿轧制方向伸长的层状组织,其在垂直于轧面方向上的平均界面间距为200 nm。这些结果表明,通过加入0.3%固溶元素Cu到... 

【文章来源】：重庆大学重庆市 211工程院校 985工程院校 教育部直属院校

【文章页数】：139 页

【学位级别】：博士

【文章目录】：
中文摘要
ABSTRACT
1 Introduction
2 Literature review
    2.1 Microstructural development of nanostructured metals
    2.2 Deformation mechanisms in nanostructured metals
        2.2.1 Slip of dislocation
        2.2.2 Slip of partial dislocations and twinning
        2.2.3 Grain boundary mediated mechanisms
    2.3 Processing methods for nanostructured materials
        2.3.1 Conventional cold rolling
        2.3.2 Description of other SPD techniques
    2.4 Mechanical Properties of nanostructured metals
    2.5 Strengthening mechanisms
        2.5.1 Grain size strengthening
        2.5.2 Solid solution strengthening
        2.5.3 Dislocation strengthening
    2.6 Strategies to improve ductility
        2.6.1 Strain hardening rate and strain rate sensitivity
        2.6.2 Bimodal microstructure
        2.6.3 Presence of nano precipitates
        2.6.4 Solute effect on ductility
    2.7 Effect of annealing on structure and mechanical properties of nanostructured metals
    2.8 Objectives of the present project
3 Experimental material and characterization techniques
    3.1 Material design
    3.2 Cold rolling
    3.3 Annealing treatment
    3.4 Mechanical testing
        3.4.1 Tensile tests
        3.4.2 Microhardness test
    3.5 Microstructure and texture characterization
        3.5.1 Optical microscopy
        3.5.2 Scanning electron microscopy （SEM）
        3.5.3 Transmission electron microscopy （TEM）
        3.5.4 X ray diffraction （XRD）
4 Structure and tensile behavior of nanostructured Al-0.3%Cu alloy
    4.1 Structure
        4.1.1 Morphology
        4.1.2 Boundary spacing
        4.1.3 Misorientation angle distribution
        4.1.4 Dislocation density
    4.2 Mechanical behavior
        4.2.1 Stress-strain curve
        4.2.2 Strain rate effects
    4.3 Discussion
        4.3.1 Effect of copper as solute on microstructural evolution
        4.3.2 Tensile behavior
        4.3.3 Strengthening mechanisms
    4.4 Summary
5 Effect of annealing on the microstructure and mechanical behaviorof nanostructured Al-0.3%Cu alloy
    5.1 Microstructure
        5.1.1 Microstructural evolution
        5.1.2 Boundary spacing
        5.1.3 Misorientation angle distribution
        5.1.4 Dislocation density
    5.2 Mechanical behavior
        5.2.1 Microhardness
        5.2.2 Tensile behavior
    5.3 Discussion
        5.3.1 Effect of copper as solute on microstructural evolution
        5.3.2 Tensile stability
        5.3.3 Strengthening mechanisms
    5.4 Summary
6 Textural evolution in nanostructured Al-0.3%Cu alloy
    6.1 Warm forged texture
    6.2 Deformation texture
    6.3 Texture gradient
    6.4 Textural evolution during annealing
        6.4.1 Coarsening and recovery region
        6.4.2 Partially recrystallized region
        6.4.3 Recrystallized region and grain growth
    6.5 Discussion
        6.5.1 Deformation texture in Al-0.3%Cu alloy
        6.5.2 Stability of Brass orientation
        6.5.3 Development of Goss orientation
    6.6 Summary
7 Conclusions and outlooks
Acknowledgements
References
Publications and presentations
    Publications
    Presentations at international conferences
    Educational background



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