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阶梯形正反螺纹搅拌针对2A12-T4铝合金 FSLW接头力学性能的影响

Effect of stepped reverse-threaded pin on mechanical properties of friction stir lap welded 2A12-T4 aluminum alloy

  • 摘要: 搅拌针上螺纹分布情况会对搅拌摩擦焊接头内部材料流动行为产生重要影响,进而影响接头成形及力学性能. 采用锥形螺纹搅拌针和阶梯形正反螺纹搅拌针进行2A12-T4铝合金搅拌摩擦搭接焊试验,对比分析了两种搅拌针下搅拌摩擦搭接焊接头横截面形貌、显微组织、拉剪性能及接头断裂位置. 结果表明,两种搅拌针下接头横截面形貌均呈现“碗状”. 然而,在阶梯形正反螺纹搅拌针焊接下搭接界面后退侧出现特有的“括号”形貌. 相对于锥形螺纹搅拌针,阶梯形正反螺纹搅拌针下的接头热力影响区与热影响区晶粒分布相差不大,但焊核区晶粒细化程度更加明显;接头在焊接速度80 mm/min下可获得最大拉剪性能,其值为10.39 kN. 阶梯形正反螺纹搅拌针下接头界面后退侧出现的“括号”形貌阻碍了裂纹向焊核区进一步扩展,断裂模式表现为拉伸断裂.

     

    Abstract: The distribution of the thread on the pin has an important effect on the material flow behavior in the friction stir welded joint, and then affects the joint formation and mechanical properties. In order to investigate cross-section morphology, microstructure, shear failure performances and fracture position of FSLW joints, the taper-threaded pin and the stepped reverse-threaded pin were used to weld 2A12-T4 aluminum alloy. The results showed that the morphologies of joints in cross section under the two types of pins presented “bowl-shaped”. However, the unique “parenthesis” morphology appears at the retreating side of joints using the stepped reverse-threaded pin. Compared with the taper-threaded pin, the grain distribution in the thermo-mechanically affected zone and heat affected zone of the joint welded by the stepped reverse-threaded pin was not different, but the grain refinement degree of stir zone was more obvious. Meanwhile, the maximum shear failure performance was 10.39 kN at the welding speed of 80 mm/min. The “parenthesis” shape on the retreating side of the joint welded by the stepped reverse-threaded pin prevented the crack from spreading to the stir zone, and the fracture mode was tensile fracture.

     

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