2219铝合金搅拌摩擦焊接头组织和性能的不均匀性研究

Non-Uniformity of Microstructure and Mechanical Properties of Friction Stir Welding Joints of 2219 Aluminum Alloy

目的针对2219铝合金搅拌摩擦焊接头受焊接热作用和机械搅拌作用的影响,极易产生组织和力学性能不均匀的情况,深入研究接头的局部力学性能,为焊接工艺优化提供理论指导。方法采用显微组织分析与数字图像相关(DIC)技术测试相结合的方法,对2219铝合金搅拌摩擦焊接头的组织和局部力学性能进行表征,并建立搅拌摩擦焊接头各区域的局部力学性能模型。结果 2219铝合金搅拌摩擦焊接头的力学性能薄弱区为热机影响区。试样断裂前该区域局部应力达到345 MPa,局部应变为18.9%,而此时母材应变仅为1.91%。结论热机影响区的组织在焊接热作用和机械搅拌的双重作用下发生了粗化和软化,导致该区的力学性能降低,是整个焊接接头的薄弱区域。

The work aims to study the local mechanical properties of joints to provide theoretical guidance for the optimization of welding process in view of that the microstructure and mechanical properties of friction stir welding joints of 2219 aluminum alloy are generally not uniform due to the effects of welding heat and mechanical stirring. The microstructure and local mechanical properties of friction stir welding joints of 2219 aluminum alloy were characterized by means of microstructure analysis and digital image correlation(DIC) technique, and the model of local mechanical properties for each area of friction stir welding joints was established. The weak area of mechanical properties of 2219 aluminum alloy friction stir welding joint was thermal mechanical affected zone(TMAZ). Before the fracture of the sample, the local stress in TMAZ reached 345 MPa and the local strain was 18.9%, while the tensile strain in base metal was only 1.91%. The microstructure of the TMAZ is coarsened and softened under the effect of welding heat and mechanical stirring, resulting in the reduction of the mechanical properties, so TMAZ is the weak area of the welding joint.