采用大载荷超低速搅拌摩擦焊工艺对2 mm厚的T2纯铜进行焊接，利用光学显微镜、扫描/透射电子显微镜、电子背散射衍射、硬度测试以及静拉伸试验对焊接接头的微观组织和力学性能进行研究. 结果表明，焊接热循环得到显著改善，有效抑制了由焊后余热带来的退火软化作用，彻底消除热影响区. 搅拌区由含有大量孪晶组织的超细晶构成，搅拌区抗拉强度和断后伸长率分别较母材提高了94%和69%. 文中提供了一种简单有效的方法，可同时提高纯铜搅拌摩擦焊搅拌区的强度和韧性.
T2 copper plates with a thickness of 2 mm were successfully joined by large-load and low-speed friction stir welding. Microstructures and mechanical properties of welding joints were investigated by optical microscopy, scanning/transmission electron microscopy, electron backscatter diffraction, microhardness measurement and tensile testing. The results showed that the thermal cycle was significantly improved in the stir zone, inhibiting the joint softening degree, while heat affected zone was eliminated as well. The stir zone consisted of the ultra-refined grain structures with abundant twin boundaries. As a result, the ultimate tensile strength and elongation were respectively enhanced by 94% and 69% compared with those of the base metal. This work provides a simple and effective method to enhance the strength and ductility of friction stir welded copper joints.
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