Experiment And Mechanical Property Evaluation Of Pulse Laser Welding Of 2219 Aluminum Alloy

Due to its high strength and low density,2219 aluminum alloy has become one of the most important lightweight structural materials in the aerospace field,and is called "aviation aluminum".At present,2219 aluminum alloy has been widely used in thin-walled components such as fuel tanks,launch vehicle cabins,aircraft panels,and high-speed rail bodies in the aerospace field.Among them,there is an urgent need for high-quality connection technology for medium and large aluminum alloy structural parts.In the current mainstream connection technology,welding,as an important connection technology,has the advantages of being able to realize the metallurgical bonding of the connection and the limitation of the types of applicable connection materials is small.For 2219 aluminum alloy materials,the current mainstream welding methods include arc welding,electron beam welding,friction stir welding,etc.The main welding defects that are easy to produce include pores,cracks,welding deformation,chain-like coarse and brittle hard eutectic,and heat-affected zone softening,etc..This article proposes the use of pulsed laser welding to weld 2219 aluminum alloy,which reduces welding defects by optimizing the range of process parameters.Analyze the microstructure characteristics of the grain morphology,texture orientation,phase composition,element distribution,etc.of the weld area,as well as mechanical properties such as tensile strength and microhardness,and explore the influence of process parameters on the microstructure and macroscopic shape of the welded joint.The influence of morphology and mechanical properties reveals the eutectic structure and the mechanism of crack generation.The main research contents and conclusions of this paper are as follows:(1)Explore pulse laser welding process parameters.Pulsed laser has unique advantages due to the intermittent heat input,but there are many related parameters and the suitable process parameter window is narrow.Therefore,the relatively suitable process parameter range is optimized first.For the pulse frequency,the parameter that best reflects the characteristics of pulsed lasers,a single factor experiment was performed.(2)Analyze the influence of pulse frequency changes on welded joints.Analyze the macroscopic morphology,including the flatness of the weld surface,whether there is spatter undercut,whether there is positive or negative overheight,etc.;analyze the microstructure characteristics of the weld,including element distribution,crystal grain morphology,phase composition,texture orientation,etc..The results show that within a certain range,with the increase of the pulse frequency,the macro morphology is gradually optimized,and the defects such as element segregation on the micro scale are also suppressed to a certain extent.(3)The mechanical properties of welded joints were tested,mainly including tensile experiments.It was found that as the pulse frequency increases within a certain range,the tensile strength gradually increases.The reasons for the increase in mechanical properties include two aspects: macro morphology and microstructure.When the pulse frequency is 27 Hz,due to the good suppression of macro and micro defects,the tensile strength of the weld is 270.3±0.9 MPa,which is about 69% of the base metal.Analyze the fracture mechanism of welded joints during stretching.The fracture has the characteristics of both brittle fracture and ductile fracture.A large number of dimples and river-like patterns can be observed from the front of the fracture.The fracture mode is both brittle fracture and ductile fracture.Transgranular fracture and intergranular fracture can be observed from the side of the fracture.