Thermo-mechanical Behaviors and Microstructure Characteristics of Ultrasonic Vibration Enhanced Friction Stir Welding

doi:10.3901/JME.2015.22.022

Abstract

Abstract: In order to utilize the ultrasonic energy to reduce the yield stress and flow stress of the metal materials during friction stir welding(FSW), the experimental system of the ultrasonic vibration enhanced friction stir welding(UVeFSW) is developed, and tests are conducted with 6061Al-T6 alloy plates. The welding load under the ultrasonic vibration are measured by real-time capturing the electrical parameters of the FSW machine and translating them to torque and force according to specific formula. Thermal cycle is measured by embedding thermal couples in specific positions. Weld cross-section size and microstructure in UVeFSW are also observed by stereomicroscope and metalloscope. They are all compared with those in conventional FSW at the same welding parameters. The results reveal that the ultrasonic vibration reduces the axial force and tool torque significantly, enlarges the weld cross-section size, refines and homogenizes the grains in weld nugget and thermo-mechanically affected zone. The measurements of the thermal cycle shows that the peak temperature of the measured points slightly decrease under ultrasonic vibration. It is inferred that the exerted ultrasonic vibration interacts with the plasticized material near the tool, decreases the yield stress and flow stress of the metals, and changes the temperature field, so that statisfactory results are achieved.

Key words: friction stir welding, microstructure, thermal cycle, ultrasonic vibration, welding load

LIU Xiaochao, WU Chuansong, ZHONG Yibin, GAO Song. Thermo-mechanical Behaviors and Microstructure Characteristics of Ultrasonic Vibration Enhanced Friction Stir Welding[J]. Journal of Mechanical Engineering, 2015, 51(22): 22-28.

References

[1] MISHRA R S，MA Zongyi. Friction stir welding and processing[J]. Materials Science and Engineering：R：Reports，2005，50(1)：1-78.
[2] 张田仓，郭德伦，陈沁刚，等. 铝合金搅拌摩擦焊技术研究[J]. 机械工程学报，2002，38(2)：127-130.ZHANG Tiancang，GUO Delun，CHEN Qingang，et al. Aluminium alloys friction stir welding technology[J]. Journal of Mechanical Engineering，2002，38(2)：127-130.
[3] NANDAN R，DEBROY T，BHADESHIAH K D H. Recent advances in friction stir welding-process，weldment structure and properties[J]. Progress in Materials Science，2008，53：980-1023.
[4] 石磊，武传松，刘会杰. 逆向差速搅拌摩擦焊接材料塑性流变和热场的数值模拟[J]. 机械工程学报，2014，50(16)：140-146. SHI Lei，WU Chuansong，LIU Huijie. Modeling material plastic flow and thermal field in reverse dual-rotation friction stir welding[J]. Journal of Mechanical Engineering，2014，50(16)：140-146.
[5] KOHN G，GREENBERG Y，MAKOVER I，et al. Laser-assisted friction stir welding[J]. Welding Journal，2002，81(2)：46-48.
[6] LIU H J，GUO N，FENG J C. Friction stir welding assisted by micro-plasma arc[C/CD]//Proceedings of the 6th International Symposium on Friction Stir Welding，Montreal，2006.
[7] 申志康. 钢的复合搅拌摩擦焊技术[D]. 兰州：兰州理工大学，2011.SHEN Zhikang. Hybrid friction stir welding technology for steel[D]. Lanzhou：Lanzhou University of Technology，2011.
[8] LUO J，WANG X J，WANG J X. New technological methods and designs of stir head in resistance friction stir welding[J]. Science and Technology of Welding & Joining，2009，14(7)：650-654.
[9] SANTOS T G，MIRANDA R M，VILACA P. Friction Stir Welding assisted by electrical Joule effect[J]. Journal of Materials Processing Technology，2014，214(10)：2127-2133.
[10] LIU X，LAN S，NI J. Electrically assisted friction stir welding for joining Al 6061 to TRIP 780 steel[J]. Journal of Materials Processing Technology，2015，219：112-123.
[11] YAO Z， KIM G Y，WANG Z，et al. Acoustic softening and residual hardening in aluminum：Modeling and experiments[J]. International Journal of Plasticity，2012，39：75-87.
[12] PARK K. Development and analysis of ultrasonic assisted friction stir welding process[D]. Michigan：The University of Michigan，2009.
[13] 贺地求，李剑，李东辉，等. 铝合金超声搅拌复合焊接[J]. 焊接学报，2011，32(12)：70-72.HE Diqiu，LI Jian，LI Donghui，et al. Study on ultrasonic stir hybrid welding of aluminium alloy[J]. Transactions of the China Welding Institution，2011，32(12)：70-72.
[14] 刘小超，武传松. 超声振动对 6061-T4 铝合金搅拌摩擦焊接头组织和性能的影响[J]. 焊接学报，2014，35(1)：49-53.LIU Xiaochao，WU Chuansong. Effect of ultrasonic vibration on microstructure and mechanical properties of friction stir welding joint of 6061-T4 aluminum alloy[J]. Transactions of the China Welding Institution，2014，35(1)：49-53.
[15] LIU X C，WU C S，RETHMEIER M，et al. Mechanical properties of 2024-T4 aluminium alloy joints in ultrasonic vibration enhanced friction stir welding[J]. China Welding，2013，22(4)：8-13.
[16] SU H，WU C S，PITTNER A，et al. Simultaneous measurement of tool torque，traverse force and axial force in friction stir welding[J]. Journal of Manufacturing Processes，2013，15(4)：495-500.
[17] 王怡嵩，孟强，刘小超，等. 超声振动对铝合金搅拌摩擦焊焊缝成形的影响[J]. 焊接，2015(3)：35-39.WANG Yisong，MENG Qiang，LIU Xiaochao，et al. Effect of ultrasonic vibration on friction stir weld formation of aluminium alloy[J]. Welding & Joining，2015(3)：35-39.
[18] 胡礼木，吕晓光，郭鹏程，等. 搅拌摩擦焊径向阻力的动态测量与分析[J]. 机械工程学报，2007，43(9)：224-227. HU Limu，Lü Xiaoguang，GUO Pengcheng，et al. Dynamic measuring and analysis on radial resistant force in friction stir welding[J]. Journal of Mechanical Engineering，2007，43(9)：224-227.
[19] 王廷，刘会杰，冯吉才，等. 7050 铝合金FSW焊接热循环及其对热影响区性能的影响[J]. 热加工工艺，2008，37(17)：22-25.WANG Ting，LIU Huijie，FENG Jicai，et al. Thermal cycle in 7050 aluminum alloy joint during friction stir welding and its effect on mechanical properties of HAZ[J]. Hot Working Technology，2008，37(17)：22-25.
[20] HWANG Y M，KANG Z W，CHIOU Y C，et al. Experimental study on temperature distributions within the workpiece during friction stir welding of aluminum alloys[J]. International Journal of Machine Tools and Manufacture，2008，48(7)：778-787.
[21] MAEDA M，LIU H，FUJII H，et al. Temperature field in the vicinity of FSW-tool during friction stir welding of aluminium alloys[J]. Welding in the World，2005，49(3-4)：69-75.