基于同质摩擦的涡流搅拌摩擦焊工艺

Vortex-friction stir welding process based on internal friction between identical materials

涡流搅拌摩擦焊(VFSW)是一项新近提出的改型工艺,其利用与工件材料同材质的棒材和外加的支撑套筒作为搅拌工具进行搅拌摩擦焊接,有望在高熔点金属的固相连接、焊接修复等领域取得工程应用。研究了转速对6061铝合金涡流搅拌摩擦焊焊缝成形和接头力学性能的影响规律。试验结果表明,在30 mm/min的焊接速度下,当转速较低时焊缝背部出现弱连接,接头强度较低;当转速较高时因工件和搅拌工具之间的界面打滑而难以形成有效的涡流式材料流动,导致焊缝无法有效成形,出现表面线状缺陷;在400~800 r/min的转速范围内,可获得良好的焊接接头。随转速增加,焊核区体积先增大后减小,但热影响区体积逐渐增大。在完全焊透的前提下,热影响区是接头软化最严重的区域,同时也是拉伸试样的断裂部位。随转速提高,接头抗拉强度先升高后降低,断后延伸率则相反。试验参数下接头的最大抗拉强度为174.8 MPa,对应的断后延伸率为6.5%。

Vortex-Friction Stir Welding(VFSW)is a newly proposed modified process,which uses a stir bar made by the material identical with the workpiece and a non-consumable holder as the friction stir tool to perform FSW.It has great potential in welding high-melting point metals and welding repair.This paper investigated the effect of rotating speed on weld formation and joint mechanical properties in VFSW of 6061 aluminium alloy.The experimental results show that at a welding speed of 30 mm/min,if the rotation speed was too low,the“kissing bond”defect appeared in the weld bottom and thus the joint strength was relatively low;if the rotation speed was too high,it was difficult to form vortex material flow due to the interface slip between the workpiece and the stir bar,so that surface linear defects appeared as the welding process cannot run.At the rotation speeds of 400-800 r/min,good weld formation could be obtained.With the increase in rotation speed,the volume of weld nugget zone first increased and then decreased,but the volume of heat affected zone gradually increased.For the defect-free weld joint,the heat affected zone was the most severely softened region of the joint,and the fracture location of the tensile specimen.With the increase in rotation speed,the ultimate tensile strength of the joint increased first,and then decreased.On the contrary,the elongation first decreased and then increased.Under the experimental conditions,the maximum ultimate tensile strength of the joint was 174.8 MPa,and the corresponding elongation of the joint was 6.5%.