2198和C24S異種鋁鋰合金攪拌摩擦焊接頭的顯微組織和力學性能Microstructures and mechanical properties of friction stir welding dissimilar 2198 and C24S Al-Li alloys

對2198和C24S異種鋁鋰合金進行攪拌摩擦焊對接試驗，分析接頭的顯微組織和力學性能。結果表明：前進側和返回側熱影響區的板條狀組織均發生了粗化，前進側熱力影響區的晶粒被拉長，返回側熱力影響區的變形晶粒周圍存在細小的再結晶晶粒，焊核區為細小的2198和C24S鋁鋰合金再結晶晶粒，且2198鋁鋰合金的再結晶晶粒更大。焊接速度在60~120 mm/min變化時，2198鋁鋰合金位于前進側的接頭抗拉強度更高；接頭拉伸試樣的斷裂均發生在2198鋁鋰合金的熱力影響區，最大抗拉強度為382 MPa，達到了2198鋁鋰合金母材抗拉強度的82.7%；接頭的焊核區、熱力影響區和熱影響區均發生軟化，焊核區中2198鋁鋰合金的硬度比C24S鋁鋰合金的更低。

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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