偏移量对铝钢异种金属搅拌摩擦焊接头微观组织及力学性能的影响

Effect of Offset on Microstructure and Mechanical Properties of Friction Stir Welded Joint of Aluminum and Steel Dissimilar Metals

利用搅拌摩擦焊(FSW),采用正偏移量(搅拌针偏钢侧)对厚度为2.5 mm的6061铝合金与Q235钢进行不同工艺的平板对接试验。使用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)及能谱仪(EDS)对不同工艺的铝/钢FSW接头进行微观组织观察,并对界面过渡区中的金属间化合物(IMC)进行表征。采用电子万能试验机对接头的力学性能进行测试。研究结果表明,在铝/钢异种金属FSW过程中,搅拌头偏移量越大,接头两种母材的相互扩散越充分;热输入量越高,界面过渡区也就越厚;铝/钢FSW接头强度取决于界面过渡区厚度与IMC种类及数量。当偏移量为0.4 mm时,转速600 r/min,速度120 mm/min时,接头强度达到124.5MPa。钢侧界面过渡区是接头最薄弱区域,金属间化合物Fe2Al5和Fe3Al对接头变形和断裂不利。

Friction stir welding of the butt plate of 6061 aluminum alloy and Q235 steel with the thickness of 2.5 mm was carried out by using a positive offset(the stirring pin is offset to steel side)and different processes.Optical microscopy(OM),scanning electron microscopy(SEM),X-ray diffractometer(XRD)and energy spectrometer(EDS)were used to observe the microstructure of aluminum alloy/steel welded joints obtained by different processes and characterize intermetallic compounds(IMC)in the intermediate transition zone.The tensile mechanical properties of joints were tested by electronic universal testing machine.The results indicate that the bigger the offset of aluminum alloy/steel FSW is,the fuller the diffusion of base metals of the joint is,and the greater the heat input is,the thicker the interface transition zone between metals is.The strength of aluminum/steel FSW joint depends on the thickness of interface transition zone and the type and quantity of IMC.When the offset is 0.4 mm,the revolving speed is 600 r/min,the welding speed is 120 mm/min,the strength of the joint reaches 124.5 MPa.Interface transition zone at steel side is the weakest area in joint.Fe2Al and Fe3Al is unfavorable to the deformation and fracture of the joint.