2198和C24S异种铝锂合金搅拌摩擦焊接头的显微组织和力学性能Microstructures and mechanical properties of friction stir welding dissimilar 2198 and C24S Al-Li alloys

对2198和C24S异种铝锂合金进行搅拌摩擦焊对接试验，分析接头的显微组织和力学性能。结果表明：前进侧和返回侧热影响区的板条状组织均发生了粗化，前进侧热力影响区的晶粒被拉长，返回侧热力影响区的变形晶粒周围存在细小的再结晶晶粒，焊核区为细小的2198和C24S铝锂合金再结晶晶粒，且2198铝锂合金的再结晶晶粒更大。焊接速度在60~120 mm/min变化时，2198铝锂合金位于前进侧的接头抗拉强度更高；接头拉伸试样的断裂均发生在2198铝锂合金的热力影响区，最大抗拉强度为382 MPa，达到了2198铝锂合金母材抗拉强度的82.7%；接头的焊核区、热力影响区和热影响区均发生软化，焊核区中2198铝锂合金的硬度比C24S铝锂合金的更低。

The friction stir butt welding of dissimilar 2198 and C24S Al-Li alloys was conducted. The microstructures and mechanical properties of the joints were analyzed. The results show that the lath-shaped grains in the heat affected zone (HAZ) of the advancing side (AS) and retreating side become coarsening. The grains in the thermal-mechanically affected zone of the advancing side are elongated, and some fine grains appear in the deformed grains in the thermal-mechanically affected zone of the retreating side. The welding nugget zone exhibits fine recrystallized grains of the 2198 and C24S Al-Li alloys, and the recrystallized grain size of the 2198 Al-Li alloy is larger than that of the C24S Al-Li alloy. With the welding speed increasing from 60 to 120 mm/min, the tensile strength of the joints is higher when the 2198 Al-Li alloys are located in the advancing side than that when the C24S Al-Li alloys are located in the advancing side. The joints are all fractured in the thermal-mechanically affected zone of the 2198 Al-Li alloys, and the highest tensile strength is 382 MPa, which reaches 82.7% of that of the 2198 Al-Li alloy. The welding nugget zone, thermal-mechanically affected zone and heat affected zone are all softened. Moreover, the microhardness of the 2198 Al-Li alloy is lower than that of the C24S Al-Li alloy in the welding nugget zone.

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