納米結(jié)構(gòu)金屬因具有較傳統(tǒng)粗晶材料高得多的強度,具有較好的工程應(yīng)用潛力。但其加工硬化能力低、塑性差,而且由于高密度的晶界和晶體缺陷所導(dǎo)致的高儲存能而使其微觀結(jié)構(gòu)的熱穩(wěn)定性差,這些問題嚴重制約了其實際應(yīng)用。探討提高納米結(jié)構(gòu)金屬力學(xué)穩(wěn)定性和熱穩(wěn)定性的途徑,具有重要意義。在本論文中,設(shè)計制備了一種納米結(jié)構(gòu)Al-0.3%Cu合金,該合金以超高純鋁（99.9996%）為基體,在基體中加入質(zhì)量比為0.3%的高純度Cu（99.99%）固溶元素。目的是利用固溶元素Cu穩(wěn)定納米結(jié)構(gòu)Al-0.3%Cu合金的微觀組織和塑性流變,以探尋一種優(yōu)化納米結(jié)構(gòu)材料的微觀組織結(jié)構(gòu)和力學(xué)性能的新的材料設(shè)計方法。通過98%形變量的高應(yīng)變冷軋變形獲得了具有納米結(jié)構(gòu)的材料,用于研究其熱穩(wěn)定性和力學(xué)性能。通過對冷軋和不同工藝下熱處理后材料的力學(xué)行為進行系統(tǒng)的測試,以及利用透射電鏡（TEM）和電子背散射衍射（EBSD）等方法對材料的微觀組織進行的系統(tǒng)表征,得到如下結(jié)論:①通過室溫98%的冷軋變形,獲得了平行于軋面而沿軋制方向伸長的層狀組織,其在垂直于軋面方向上的平均界面間距為200 nm。這些結(jié)果表明,通過加入0.3%固溶元素Cu到... 

【文章來源】：重慶大學(xué)重慶市 211工程院校 985工程院校 教育部直屬院校

【文章頁數(shù)】：139 頁

【學(xué)位級別】：博士

【文章目錄】：
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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