铝合金大功率超声波焊接界面及接头性能研究

Analysis of Welding Interface and Joint Properties of High Power Ultrasonic Welding of Aluminum Alloy

尽管大功率超声波焊接更适合异种金属的焊接,在汽车轻量化上应用的研究较少。研究6061-T6铝合金与纯铜、6061-T6铝合金与DC04钢大功率超声波焊接的界面及接头性能,主要包括界面的温升、中间相的生成以及接头的力学性能、拉伸断口形貌。结果表明,在钢/铝超声波焊接中,在焊接时间1 s、压力1.98 kN和振幅27μm时,界面生成厚度为1.70μm、主要成分为FeAl3和Fe2Al5且连续分布的中间相;近一半的超声功率转化为界面能量;焊接区域面积明显大于焊头端面;界面发生了较大的塑性变形,存在明显的机械互锁;接头的最高强度为3.95 kN,拉伸破坏行为为界面式破坏,且断裂模式为韧性-脆性复合断裂。在铜/铝焊接中,在焊接时间0.54s、压力1.45kN和振幅25μm时,界面生成厚度为1.95μm、主要成分为Al2Cu的中间相,获得的接头最高强度为3.20 kN,其拉伸破坏行为为拉拔式破坏。研究了中间相厚度与接头强度的关系,适当的IMC厚度能促进连接。

Although high-power ultrasonic welding(USW)is better suitable for joining dissimilar metals,there is few studies on application of this welding method in automobile lightweight.The interface performances and joint properties,including interface temperature rise,intermetallic compound(IMC)growth,joint strength and fracture morphology,in 6061-T6 aluminum alloy dissimilar high-power USW are studied.In USW of Steel/Al combination,at 1 s welding time,1.98 kN normal force,and 27μm amplitude,a continuous IMC layer with a thickness of 1.7μm occurs at welding interface.The IMC is primarily composed of FeAl3 and Fe2 Al5.About half of the ultrasonic power is converted into interfacial energy.The welding zone is significantly larger than the sonotrode tip area.High plastic deformation and obvious mechanical interlocking occur at the interface.The obtained highest lap-shear strength of Steel/Al joint were 3.95 kN.The tensile failure behavior of the joint is interface failure,and the fracture mode of the joint is ductile-brittle hybrid fracture.In USW of Cu/Al combination,at 0.54 s time,1.45 kN normal force,and 25μm amplitude,the IMC layer with thickness of 1.95μm at the interface is primarily composed of Al2 Cu;the obtained highest lap-shear strength of Cu/Al joint is 3.20 kN,and the tensile failure behavior of the joint is pull-out failure.The relationship between IMC thickness and joint strength shows that proper IMC layer thickness can improve the joints strength.