焊后时效对Al-6.7Zn-1.8Mg-0.2Cu高强铝合金搅拌摩擦焊接头组织和性能的影响  

Effect of post-welding aging on the microstructure and mechanical properties of high-strength Al-6.7Zn-1.8Mg-0.2Cu aluminum alloy joints prepared by friction stir welding

作　　者：胡莎莎 邱诚[1] 张大童[1] HU Shasha;QIU Cheng;ZHANG Datong(National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials,South China University of Technology,Guangzhou 510641,China)

机构地区：[1]华南理工大学,国家金属材料近净成形工程技术研究中心,广州510640

出　　处：《焊接学报》2025年第1期41-47,共7页Transactions of The China Welding Institution

摘　　要：采用搅拌摩擦焊(friction stir welding,FSW)对3.2 mm厚度的Al-6.7Zn-1.8Mg-0.2Cu铝合金挤压板材进行焊接,并对焊接接头进行焊后时效热处理,即人工时效(artificial ageing,AA)120℃×24 h.采用扫描电子显微镜(scanning electron microscopy,SEM)、透射电子显微镜(transmission electron microscopy,TEM)、硬度试验和拉伸试验等对焊后接头和时效接头进行研究.结果表明,Al-6.7Zn-1.8Mg-0.2Cu高强铝合金FSW接头抗拉强度为470 MPa,焊接系数为80.0%,断后伸长率为10.1%.采用焊后AA能有效提高接头的强度,其抗拉强度为525 MPa,相比焊态接头提高11.8%,达到母材(base material,BM)的89.6%,断后伸长率为8.5%.FSW过程中受摩擦热影响热力影响区(thermo-mechanically affected zone,TMAZ)和焊核区(nugget zone,NZ)的析出相溶解随后冷却再析出,其中析出相主要是η'相,在热影响区(heat-affected zone,HAZ)主要发生GP区(Guinier-Preston zone)的溶解和η'相的粗化,在不同热输入下析出相逐渐由溶解转变为粗化.焊后时效使得GP区析出和发生GP区向η'相的转变,在HAZ处已存的η'相转变成粗大的η相.接头硬度曲线呈明显W形,FSW接头断裂在NZ,焊后时效接头断裂在HAZ.Friction stir welding(FSW)is used to weld Al-6.7Zn-1.8Mg-0.2Cu aluminum alloy sheet with 3.2 mm thickness,and the welded joint is subjected to post-welding aging heat treatment,and that is artificial ageing(AA)120℃×24 h.The welded and aged joints are studied by scanning electron microscopy(SEM),transmission electron microscopy(TEM),hardness test and tensile test.The results show that the tensile strength of the joint is 470 MPa,the welding coefficient is 80.0%,and the elongation is 10.1%.AA could effectively improve the tensile strength of the joint,which is 525 MPa,89.6%of the base material(BM).Compared to as-welded joint increases 11.8%.And the elongation is 8.5%.In the FSW process,the precipitated phases in thermomechanically affected zone(TMAZ)and nugget zone(NZ)are dissolved and then precipitated after cooling,in which the precipitated phase is mainlyη'phase,and the dissolution of GP zone(Guinier-Preston zone)and coarsening ofη'phase mainly occurred in the heat-affected zone(HAZ),and the precipitated phase gradually changed from dissolution to coarsening under different heat input.After welding ageing,GP zone precipitates and GP zone transforms toη'phase,and the existingη'phase at HAZ transforms into coarseηphase.The hardness curve of the joint is obviously W-shaped,the fracture of the FSW joint is in the NZ,and the fracture of the post-welding aging joint is in the HAZ.

关 键 词：搅拌摩擦焊 Al-6.7Zn-1.8Mg-0.2Cu铝合金 焊后热处理 微观组织 力学性能 

分 类 号：TG453.9[金属学及工艺—焊接]