This research program evaluates the residual properties of 7136-T76511 aluminum extrusions joined through friction stir welding (FSW). AA 7136 is a new aluminum alloy developed by Universal Alloy Corporation for high strength aerospace applications that also demand good corrosion resistance, such as those on the Boeing 787 or the Airbus A3 80. Mechanical and corrosion testing were performed on the baseline material and on panels friction stir welded at 175, 225, 250, 300, 350 and 400 RPM (all other welding parameters were held constant). Mechanical test results demonstrate that the highest joint efficiency, 74%, is achieved at 350 RPM, but for each weld condition, the elongation of the welded material is significantly reduced, 50 - 75%, from the baseline value. Fracture of the tensile specimens consistently occurred on the retreating side of the weld along the interface between the heat affected zone (HAZ) and the thermo-mechanically affected zone (TMAZ), independent of the rotational speed. Examination of fracture surfaces through SEM revealed microvoid nucleation and coalescence around secondary phase particles in the microstructure, as well as numerous stepped or laminar facets characteristic to both the baseline and welded conditions. Exfoliation corrosion testing revealed a performance gradient across the weld with the weld nugget rating the poorest at EC and the heat affected zone rating the best at EA. Qualitative assessment of corrosion resistance is supported by mass loss calculations between the baseline and welded conditions.
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机译:该研究程序评估了通过摩擦搅拌焊接(FSW)连接的7136-T76511铝挤出物的剩余性能。 AA 7136是由通用合金公司开发的新型铝合金,用于高强度航空航天应用,也需要良好的耐腐蚀性,例如波音787或空中客车A3 80。在基线材料和面板上进行机械和腐蚀测试摩擦搅拌焊接在175,225,250,300,350和400rpm(所有其他焊接参数都保持恒定)。机械测试结果表明,最高的关节效率为74%,以350rpm实现,但对于每个焊接条件,焊接材料的伸长率显着降低50-75%,从基线值下降。沿着热影响区(HAZ)与热机械受影响区(TMAZ)之间的界面,焊接侧的裂缝始终发生在焊缝的后退侧。通过SEM通过SEM显示断裂表面的微观核细胞和聚结在微观结构中的二次相粒子上,以及与基线和焊接条件的许多阶梯或层面特性。去角质腐蚀测试在焊缝中揭示了焊缝的性能梯度,焊缝在EC和热影响区域的偏置中达到最贫困的区域。基线与焊接条件之间的质量损失计算支持定性评估耐腐蚀性。
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