鋁合金(AA6061-T6)因其比強(qiáng)度高和成本低,在交通車輛和電子行業(yè)的很多結(jié)構(gòu)件中得到大量應(yīng)用。同時,鎂合金(AZ31B)因其重量輕和比剛度高,作為另一種輕量化材料也吸引了人們的特殊關(guān)注。為了發(fā)揮兩種材料的優(yōu)勢,如何成功地將其高質(zhì)量連接,構(gòu)成異質(zhì)材料復(fù)合構(gòu)件,是亟待解決的問題。過去曾嘗試?yán)酶鞣N熔焊工藝連接AA6061-T6和AZ3IB,但因接頭強(qiáng)度低,基本沒有吸引力。另外,熔焊接頭中形成大量的脆性金屬間化合物(IMCs),進(jìn)一步降低了接頭強(qiáng)度,限制了其工程應(yīng)用。雖然攪拌摩擦焊接(FSW)作為固相連接技術(shù)能夠產(chǎn)生令人滿意的AA6061-T6/AZ31B異質(zhì)接頭,但焊縫中仍然形成IMCs,接頭性能仍不夠高。此外,常規(guī)FSW需要很大的軸向壓力和扭矩。在AA6061-T6和AZ31B攪拌摩擦焊接時,為了通過抑制IMCs的形成來提高接頭強(qiáng)度,并通過降低焊接載荷來減少攪拌頭磨損,本研究提出施加超聲振動來輔助FSW過程。攪拌摩擦焊接過程中在攪拌區(qū)(SZ)輔加超聲振動,有助于增強(qiáng)異質(zhì)材料的混合及抑制缺陷的形成。為了有效地實(shí)施超聲輔助攪拌摩擦焊工藝,在FSW設(shè)備上恰當(dāng)?shù)卦黾痈鞣N超聲發(fā)生和作用部件是保證...

【文章頁數(shù)】：226 頁

【學(xué)位級別】：博士

【文章目錄】：
Abstract
摘要
Chapter 1. Introduction
    1.1 Research significance
    1.2 IMCs formation in joining of AA6061-T6/AZ31B Mg alloy
    1.3 Friction stir spot welding of AA6061-T6/AZ31B alloys
    1.4 Friction stir welding process
    1.5 Friction stir welding of AA6061-T6/AZ31B Mg alloy
        1.5.1 Macro and microstructure analysis
        1.5.2 IMCs characterization
        1.5.3 Mechanical properties
        1.5.4 Variants in the FSW process
    1.6 Research status of ultrasonic-assisted FSW
        1.6.1 Ultrasonic assisted FSW of Al alloys
        1.6.2 Ultrasonic assisted FSW of Al and Mg alloys
    1.7 Other approaches for IMCs suppression
    1.8 Objectives of the Study
Chapter 2. Design and development of the ultrasonic vibration system
    2.1 Ultrasonic components
    2.2 FEM model of ultrasonic horn
        2.2.1 Modal analysis of simple horn
        2.2.2 Modal analysis of complex horn
        2.2.3 Harmonic analysis of simple horn
        2.2.4 Harmonic analysis of complex horn
    2.3 Integration of ultrasonic vibration system with the FSW machine
    2.4 Validation of simulated results
        2.4.1 Simple horn
        2.4.2 Complex horn
    2.5 Hollow vs Solid FSW tool
        2.5.1 Advantages of hollow FSW tool with respect to the solid tool
        2.5.2 Calculation of deflection at the tool end
    2.6 Effect of variable ultrasonic power on the joint quality
    2.7 Summary
Chapter 3. Friction stir butt welding of AA6061-T6/AZ31B Mg alloy
    3.1 The UVaFSW system and test conditions
    3.2 Axial downward force, torque and power analysis
        3.2.1 Axial downward force
        3.2.2 Tool torque variation
        3.2.3 Power input
    3.3 Weld morphology and macrostructure
    3.4 Microstructural characterization
        3.4.1 Regional microstructure
        3.4.2 Interfacial microstructure
    3.5 Scanning electron microscopy characterization
    3.6 Intermetallic characterization across the AA6061-T6/AZ31B Mg alloy interface
        3.6.1 Effects of rotation speed on IMCs
        3.6.2 Effects of welding speed on IMCs
    3.7 Mechanical properties
        3.7.1 Micro-hardness profile
        3.7.2 Uniaxial tensile testing
    3.8 Fractography
    3.9 Summary
Chapter 4. Friction stir lap welding of AA6061-T6/AZ31B Mg alloy
    4.1 U-FSLW system and test conditions
    4.2 Weld morphology and optical micrographs
    4.3 Scanning electron microscopic analysis
    4.4 Material flow and EBSD characterization
    4.5 Elemental mapping of IMCs region
    4.6 The IMCs characterization
        4.6.1 IMCs in case Ⅰ(600/100)
        4.6.2 IMCs in case Ⅱ(800/100)
        4.6.3 IMCs in case Ⅲ(1000/100)
    4.7 XRD analysis of IMCs regions
    4.8 Mechanical testing
        4.8.1 Shear failure load and joint efficiency
        4.8.2 Micro-hardness
    4.9 Fractography
    4.10 Summary
Chapter 5. Friction stir lap welding of AZ31B Mg/AA6061-T6 and the effects ofNi interlayer addition
    5.1 FSLW and U-FSLW of AZ31B Mg/AA6061-T6 and test conditions
        5.1.1 Weld morphology and optical micrographs
        5.1.2 IMCs characterization
        5.1.3 Mechanical properties
    5.2 Friction stir lap welding of dissimilar AZ31B Mg/AA6061-T6 with theNi interlayer and test conditions
        5.2.1 Macro-structure analysis
        5.2.2 Material mixing and IMCs characterization across SZ
        5.2.3 Material mixing and IMCs characterization across weld interface
        5.2.4 Mechanical properties
        5.2.5 Fractography
    5.3 Summary
Chapter 6. Conclusion and Future work
    6.1 Conclusion
    6.2 Future work
References
Acknowledgement
Published and ongoing work
    Peer-reviewed journals
    Academic conferences
Patent
Awards
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