AA6061-T6/AZ31B异质FSW接头金属间化合物抑制和性能改善的机理研究

发布时间：2025-02-06 18:38

　　铝合金(AA6061-T6)因其比强度高和成本低,在交通车辆和电子行业的很多结构件中得到大量应用。同时,镁合金(AZ31B)因其重量轻和比刚度高,作为另一种轻量化材料也吸引了人们的特殊关注。为了发挥两种材料的优势,如何成功地将其高质量连接,构成异质材料复合构件,是亟待解决的问题。过去曾尝试利用各种熔焊工艺连接AA6061-T6和AZ3IB,但因接头强度低,基本没有吸引力。另外,熔焊接头中形成大量的脆性金属间化合物(IMCs),进一步降低了接头强度,限制了其工程应用。虽然搅拌摩擦焊接(FSW)作为固相连接技术能够产生令人满意的AA6061-T6/AZ31B异质接头,但焊缝中仍然形成IMCs,接头性能仍不够高。此外,常规FSW需要很大的轴向压力和扭矩。在AA6061-T6和AZ31B搅拌摩擦焊接时,为了通过抑制IMCs的形成来提高接头强度,并通过降低焊接载荷来减少搅拌头磨损,本研究提出施加超声振动来辅助FSW过程。搅拌摩擦焊接过程中在搅拌区(SZ)辅加超声振动,有助于增强异质材料的混合及抑制缺陷的形成。为了有效地实施超声辅助搅拌摩擦焊工艺,在FSW设备上恰当地增加各种超声发生和作用部件是保证...

【文章页数】：226 页

【学位级别】：博士

【文章目录】：
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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