Effect of Postweld Heat Treatment on Mechanical Properties and Microstructure of 6061-T6 Aluminium Alloy Laser-MIG Composite Welded Joint
The effect of postweld heat treatment on the internal microstructure and mechanical properties of the welded 6061-T6 alu-minium alloy with laser-MIG composite welding was analyzed by single stage ageing and solution+ageing heat treatment on the weld-ed samples.The results show that postweld heat treatment has no obvious effect on the microstructure of the weld zone,but the grains are refined to different degrees.The hardness of the single stage ageing joint is increased by 15.7 HV,and the hardness of the joint un-der solution+ageing heat treatment system is increased by 18.6 HV.Compared with the joint without postweld heat treatment,the tensile strength of the joint under single stage ageing system is increased by 18 MPa,and the tensile strength under solution+ageing sys-tem is increased by 30 MPa.After single stage ageing and solution+ageing,the dimple at the joint becomes shallow,the plasticity de-creases,the strength increases,and the fracture position of the joint changes from the HAZ to the weld after solution+ageing.
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