| 6016 aluminum alloy is a kind of Al-Mg-Si alloy,it can be widely used in lightweight body manufacturing.In this Paper,Firstly,the laser welding process and aging behavior of 1mm thickness 6016 Aluminum Alloy will be studied,the welding process window of butt joint and lap joint is determined,the microstructure of weld joint is observed,and the mechanical properties are measured.Secondly,the effect of welding heat input on the microstructure and properties of welded joints is discussed.Lastly,the aging kinetics of post-weld heat treatment joint is analyzed,and the mechanical properties of joints under different aging conditions are predicted.The specific research results are as follows:?1?Welding process window of butt welding is as following:defocusing amount range from 15 mm to 20 mm,welding power range from 3kW to 4kW,welding speed range from 1.6 m/min to 3.6 m/min.As the defocusing amount increase and the welding power decrease,the welding process window of butt welding becomes large.?2?Welding process window of lap welding is as following:defocusing amount is 0 mm,welding power range from 3.5kW to 5.5kW,welding speed range from 3 m/min to 7.2 m/min.As the defocusing amount decrease and the welding power decrease,the welding process window of lap welding becomes large.?3?Self-fusible welding Parameters have obvious influence on the weld shape and porosity defects.As heat input increases,the welding width and excess weld metal increase,so the section area of weld becomes large.In addition,with the increase of heat input,the weld joint is easy to emerge defects such as blowhole,which is not conducive to the improvement of welding joint performance.?4?The microstructure of self-fusible welding joint is dendritic structure,metallurgical structure is composed of?-aluminum?Al12Fe3Si and Al5FeSi.During TEM observation,strengthening phase can't be found.?5?Welding joint performance can be influence by welding process.Test show that the hardness of weld center is lower than base metal,softening behavior can be existed in weld beam.In addition,as the heat input increase,the hardness of weld center will decrease.The highest tensile property of butt welded joint can be obtained under the welding Parameters as the defocusing amount is 20 mm,welding power is 3.5kW,welding speed is 2.4 m/min,and the highest tensile property of lap welded joint can be obtained under the welding Parameters as the defocusing amount is 0 mm,welding power is 6kW,welding speed is 6.4 m/min.?6?Aging treatment can prominently improve the mechanical properties of 6016 aluminum alloy welded joints.For the welded joint obtained under the defocusing amount is 0 mm?welding power is 6kW?welding speed is 6.4 m/min,aging process?180?+10 h?can enhance the hardness of the weld center from 58 HV to 82 HV,so does the tensile property can be enhanced from 180 MPa to 274 MPa.Analysis on the microstructure shows that strengthening phase precipitated during the aging process,which can improve the mechanical properties of the joint.?7?Aging kinetic analysis shows that the aging behavior of 6016aluminum welding joint matches the Johnson-Mehl-Avrami?JMA?equation.The change regulation between volume fraction of strengthening phase?He?and aging time?t?is as the following equation:He=1-exp[-?Dt?n],D=exp?-30690/RT+7.7652?,n=0.0066T-1.8428.According to the equation,the aging behavior of 6016 aluminum welding joint can be predicted at the aging temperature from 140? to 200?.In addition,the diffusion activation energy of welding joint is 31 KJ,which shows that GP zones can be formed during the aging process.The research in this Paper can provide reference for the connection of6016 aluminum alloy sheet under laser welding,the aging kinetics model of 6016 aluminum alloy welding joint established in this Paper can also have a positive reference and guidance on the optimization of aging treatment and improvement of mechanical properties. |
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