7075铝合金高速搅拌摩擦焊材料流动行为及性能研究

目的 针对7075–O铝合金高焊速、高转速搅拌摩擦焊接缺陷多、质量差等问题，研究焊接接头材料流动对焊缝性能的影响。方法 选用焊接速度1 000 mm/min，搅拌转速分别为1 000、1 200、1 600、1 700 r/min的条件对7075–O铝合金板进行搅拌摩擦焊接，分析不同焊接工艺参数下焊接接头的显微组织及力学性能。同时，利用Fluent软件模拟7075–O铝合金搅拌摩擦焊接过程中的材料流动场分布，分析焊接材料流动与缺陷形成的关系。结果 利用7075–O铝合金三维流动模型，预测出高焊速条件下焊缝前进侧形成一个低压区，孔洞等缺陷易出现在此区域，数值模拟预测与试验结果吻合。在高焊接速度1 000 mm/min、焊接转速1 200 r/min时，焊缝表面光滑平整，焊核区域的硬度分布更加均匀。结论 随着搅拌转速从1 000 r/min增大到1 700 r/min，热输入量逐渐增大，孔洞缺陷由隧道型孔洞转变为不连续的小孔。同时，随着搅拌转速的增大，焊缝高硬度区域的宽度先增大而后降低。当搅拌转速为1 200 r/min时得到了优质的焊接接头，焊缝焊核区硬度分布均匀，硬度值最高为176HV。

Material Flow Behaviors and Properties of 7075 Aluminum Alloy under High Speed Friction Stir Welding

The work aims to study the effects of material flow of welded joint on weld properties of 7075-O aluminum alloy to solve the problems of high welding speed and high speed friction stir welding defects and poor quality.Friction stir welding of 7075-O aluminum alloy plates were carried out at welding speed of 1 000 mm/min and rotating speed of 1 000, 1 200, 1 600, 1 700 r/min, respectively. The microstructure and mechanical properties of welded joints under different welding parameters were analyzed. Simultaneously, the Fluent software was used to simulate the material flow field distribution in the friction stir welding process of 7075-O aluminum alloy, and the relationship between welding material flow and defect formation was analyzed. The results showed that using the 3D flow model of 7075-O aluminum alloy, it was predicted that a low pressure zone can be formed in the forward side of the weld under the condition of high welding speed, and holes and other defects were likely to appear in this zone. The experimental results were in good agreement with those predicted by numerical simulation. At the high welding speed of 1 000 mm/min and stirring speed of 1 200 r/min, the weld surface was smooth and the hardness distribution in the core area was more uniform. As the rotation speed increases from 1 000 r/min to 1 700 r/min, the heat input gradually increases, and the hole defects change from tunnel holes to discontinuous holes. In addition, the width of the hardened zone increases first and then decreases with the increase of stirring speed. When the rotation speed is 1 200 r/min, the welded joint with high quality is obtained. The hardness distribution in the weld nugget zone is uniform, and the maximum hardness value is 176HV.