基于“热导拘束+局部变形强化”的铝合金焊轧复合成形方法  

Compound Technique of Welding and Rolling for Aluminum Alloy Based on Thermal Conductivity Constraint and Local Deformation Strengthening

作　　者：宋刚[1] 程继文 刘振夫 SONG Gang;CHENG Jiwen;LIU Zhenfu(School of Materials Science and Engineering,Dalian University of Technology,Dalian 116024)

机构地区：[1]大连理工大学材料科学与工程学院,大连116024

出　　处：《机械工程学报》2020年第8期85-91,共7页Journal of Mechanical Engineering

基　　金：国家自然科学基金资助项目(U1764251,U1960111)。

摘　　要：铝合金尤其是热处理强化铝合金焊后不可避免会出现热影响区软化现象,导致焊接接头的力学性能显著下降。基于热导拘束+局部变形强化构想,提出一种铝合金焊轧复合成形方法,系统分析铜垫强制冷却非熔化极惰性气体保护电弧焊(Tungsten inert gas,TIG)填丝对接焊及焊后轧制复合工艺对5083-O和6061-T6异种铝合金焊接接头组织和力学性能的影响。结果表明,采用焊轧复合成形方法,能够得到成形良好且无缺陷的铝合金对接接头,通过轧制使焊接接头同时发生了纵向变形和横向变形;焊后轧制可以压实铝合金焊缝组织,有效降低焊接接头部分熔化区的宽度,同时热影响区(包括固溶区和过时效软化区)晶粒发生位向改变甚至转动现象;与自由冷却焊接工艺相比,采用铜垫冷却的焊接接头6061-T6侧软化区硬度升高且向焊缝中心产生明显偏移,焊后轧制使两种冷却方式的焊接接头的整体硬度均得到大幅度提升,其中软化最严重位置硬度值由59.5HV提高到84.4HV,提升幅度为41.8%;两种冷却方式的焊接接头轧制后接头的抗拉强度均大幅度提升,其中铜垫冷却焊轧复合成形与自由冷却焊接接头相比,试样抗拉强度由197.0MPa提升到288.6MPa,提升幅度为46.5%,与5083-O母材的抗拉强度相当,断后伸长率由5.88%提升到8.85%,断裂位置由6061-T6侧热影响区转移至5083-O侧母材。The softening of heat affected zone(HAZ)inevitably occur after welding of aluminum alloy,especially for heat treatment strengthened aluminum alloy,which leads to the significant decrease of mechanical properties of welded joints.Based on the concept of thermal conductance constrain and local deformation strengthening,a compound technique of welding and rolling for aluminum alloy is proposed,and the effect of the compound technique of tungsten inert gas(TIG)filler wire butt welding with copper pad cooling and rolling on microstructure and mechanical properties of 5083-O and 6061-T6 dissimilar aluminum alloy welded joints is systematically analyzed.The results show that the defect-free and well-formed aluminum alloy butt joints can be obtained by welding-rolling composite forming.The longitudinal and transverse deformations of the welded joints occur simultaneously by rolling.This technique has several advantages over welding alone.These include obvious compaction of weld microstructure,effectively reduction of weld melting zone width,and violent rotation of grain in the heat affected zone(including the solid solution region and the overaging softening region).Compared with the free-cooling welding process,the hardness of the softened zone on the 6061-T6 side of the welded joint with copper pads cooling is increased and the severely softened position is significantly offset to the weld zone.Post-weld rolling greatly increase the overall hardness of the welded joints with two cooling methods.The hardness value at the most severely softened position is increased from 59.5 HV to 84.4 HV,an increase of 41.8%.Compared with free-cooled joints,the tensile strength of the samples by the composite forming with copper pad cooling increases from 197.0 MPa to 288.6 MPa,an increase of 46.5%,which is equivalent to the tensile strength of the 5083-O base material.As well as the elongation is increased from 5.88%to 8.85%.The tensile fracture position is transferred from the 6061-T6 side heat affected zone to the 5083-O side base m

关 键 词：铝合金 热影响区软化 焊接 局部变形强化 复合成形 

分 类 号：TG457[金属学及工艺—焊接]