Evaluation Of Mechanical Properties And Formability Of Laser Welding Joints Of 6063 Aluminum Alloy

Aluminum alloy is one of the main materials for lightweight design of mobile devices.As an efficient,precise and automatic welding process,laser welding combines high-quality materials with advanced technology is an inevitable trend of industrial development.Therefore,laser welding of aluminum alloy has certain research value.Due to the non-uniformity of welded joints,it is necessary to study the deformation and fracture behavior of welded joints under different stress states.In this paper,the butt joint and T-joint of 6063 aluminum alloy laser welding with thickness of 2 mm and 5 mm are studied.The microstructure and properties of the welded joint were analyzed by microstructure,microhardness,tensile test,bending test and cupping test.Using grid strain method and digital image correlation(DIC)to monitored the strain nephogram of butt joint in different forms of tensile process,With the help of Hollomon hardening model,the mathematical relationship between base metal and weld material parameters was established,and the effectiveness of the weld evaluation method was verified by finite element simulation.For T-joints,the strength performance and fracture behavior under tensile and bending loads were analyzed by electrical measurement method.The test results show that the ' softening ' phenomenon occurs in the weld zone,and the tensile properties,bending properties and forming properties of the welded joint are lower than those of the base metal.The weak position of 2 mm butt joint is the fusion zone at the edge of the weld,and the weak position of 5 mm butt joint is the weld center.The strength of the upper fusion zone of T-joint is higher than that of the lower fusion zone.It is necessary to avoid the weak area as the main bearing position in engineering application.Hollomon model can accurately fit the longitudinal tensile hardening curve of base metal and butt joint.Based on the assumption of equal strain,the mathematical relationship between the parameters of base metal and weld material is established.The error between the calculated value and the measured value of the true stress of the weld is within 4 %.Finally,the effectiveness of this evaluation method is verified by finite element simulation,which lays a theoretical foundation for accurately obtaining the material characterization of weld seam in engineering practice,predicting the joint performance by finite element method,evaluating the joint performance and improving the welding process.In addition,the tensile mechanical behavior of base metal and butt joint can be described in detail by grid strain method and DIC,and the error is not more than 2 %.For T-joints,the strain gauge data show that the initiation positions of transverse tensile,longitudinal tensile and lateral bending are different,which provides theoretical support for the fracture behavior of T-joints during service.