Research On Laser-TIG Hybrid Additive Manufacturing Process And Mechanical Properties Of 2219 Aluminum Alloy

2219 aluminum alloy is an important lightweight material,which is widely used in aerospace manufacturing industries such as aircraft and rocket.Additive manufacturing has become one of the effective ways of high quality aluminum alloy manufacturing because of excellent“small domain forming-layer by layer accumulation”feature.It does not need the traditional mold and has great processing flexibility,which can greatly shorten the process cycle and reduce the manufacturing cost.The traditional single heat source（laser or TIG）additive process for preparing the 2219 aluminum alloy specimen has problems such as easy defects and unreliable properties.In this research,a new method of laser-TIG hybrid additive manufacturing was proposed to increase the process stability,solve the problems of high reflectivity of aluminum alloy to laser,high heat input and poor properties of arc additive manufacturing.By comparing with TIG arc additive manufacturing,the effect of laser energy on microstructure evolution was investigated,and the relationship between microstructure and mechanical properties was revealed.The main research contents and conclusions are as follows:（1）Firstly,according to the surface morphology of single layer,2219 aluminum alloy thin-walled structure was prepared by selecting appropriate process parameters,including laser power,arc parameters,wire feeding speed and scanning speed,which provided the basis for the subsequent analysis of microstructure evolution and mechanical property detection.（2）Compared with single TIG additive,the microstructure evolution of laser-TIG hybrid was studied.In the aspect of microstructure,the striations of each layer could be divided into two regions:arc region（AZ）and laser region（LZ）.The grain size in LZ was significantly refined,and the segregation of Cu element was relieved,and the distribution tended to be uniform.EBSD analysis showed that the orientation of local crystal texture changed,and the morphology and composition of precipitates in AZ and LZ were also different.（3）Comparing the microhardness and tensile properties of TIG and laser-TIG spcimens,it was found that the average hardness value of laser-TIG specimen was 92.6±3.7 HV_0.1,which was 16%higher than that of TIG specimen,and the LZ value was higher than that of AZ.In addition,the yield strength,tensile strength and elongation of laser-TIG hybrid were155.5±7.9 MPa and 301.5±16.7 MPa,with increased by 10.8%and 8.3%,respectively.According to the characteristics of the cross-section and longitudinal section of the tensile fracture,it was found that the number of eutectic in the AZ was large.The eutectics were gathered in the grain boundary as network.The tensile fracture mode was mainly intergranular fracture;Amount of granular eutectics in LZ were dispersed in the grain,and the fracture mode became transgranular fracture.