热处理对6005A铝合金激光焊接头组织和性能的影响

高速列车车体轻量化制造的迫切需求,使得铝合金结构在车体制造中得到广泛应用,而铝合金焊接也成为高铁车体制造的关键工艺。本文采用激光填丝焊方法焊接6005A-T6铝合金,并对焊接接头进行了固溶/时效热处理。利用扫描电镜、XRD能谱分析及拉伸实验,对焊后热处理的焊接接头组织及性能进行研究。研究发现,与母材相比,由于焊接接头中Mg2Si强化相的消失,使得6005A铝合金激光填丝焊接接头拉伸性能下降。通过对焊接接头进行的固溶/时效焊后热处理,实现了焊接接头中β″相、β′相和Q′相的强化相析出,而强化相的析出有利于焊接接头性能的改善。显微硬度实验表明,焊后经热处理的焊接接头,各区域显微硬度显著提高。随着固溶时间的增加,焊接接头经时效处理达到峰时效状态所需的时间减少。基于焊接接头硬度比较,确定550℃固溶1.5 h/175℃时效8 h为优化的焊后热处理规范。采用优化的焊后热处理规范,焊接接头的拉伸强度增加至340 MPa,高于母材的拉伸强度;热处理后接头延伸率为11.6%,达到母材延伸率的65.2%。采用固溶/时效焊后热处理方式可提高激光焊接接头的性能。

Effect of heat treatment on microstructure and property of 6005A aluminum alloy laser welding joint

To meet the lightweight requirement in high speed train structure,the aluminum structure has been widely utilized in the fabrication of the train body,and welding of aluminum alloy has become the essential process for the fabrication of the train body.In this paper,6005 A-T6 aluminum alloy was laser welded with filler wire.At the same time,the"soild solution/aging"heat treatment was conducted on the welding joint.Based on electron microscopy investigation,XRD analysis and tensile experiment,microstructure and property of welding joint after post-weld heat treatment was studied.After laser welding,tensile property of the welding joint decreased compared with the substrate of 6005 A,which was attributed to the disappearance of Mg2Si strengthening phase at the welding joint.After the post-weld heat treatment of"soild solution/aging",β″phase,β′phase and Q′phase precipitated in welding joint,which was beneficial to its property.After the heat treatment,microhardness of the welding joint increased compared with that only treated by laser welding.Microhardness measurement show that aging time of"solid solution/aging"heat treatment needed to reach peak effect decreased with the increase of solid solution time.Based on comparisons of hardness distribution of welding joint,550℃solid state 1.5 h/175℃aging 8 h was selected as the optimized post-weld heat treatment parameters.Tensile property of the welding joint was increased to 340 MPa under the optimized heat treatment,which was higher than that of the substrate.Meanwhile,the elongation rate was improved to 11.6%after the heat treatment,which was 65.2%of that of the substrate.In conclusion,the property of welding joint was improved by the"soild solution/aging"heat treatment.