Study On Laser-arc Hybrid Additive Manufacturing For Block Structure Of Aluminum Alloy

Aluminum alloy has been widely used in aerospace,automobile transportation,electronic communication and other fields because of its advantages such as low density,high specific strength,strong corrosion resistance,high thermal conductivity,easy processing and low cost.It is difficult to manufacture complex block structure of aluminium alloy by traditional manufacturing technology(such as casting),with the problem of long production cycle and defects of pore or inclusion in the sample.Additive manufacturing technology is a bottom-up and layer-by-layer cumulative manufacturing method,which has great processing flexibility and can realize the manufacturing of composite structures with high degree of freedom.In this paper,the laser-arc hybrid additive manufacturing of aluminium alloy structure was explored.Compared with the laser additive manufacturing and arc additive manufacturing technology which is using wire as raw material,the laser-arc hybrid additive manufacturing improves the problems of high reflectivity of aluminium alloy to laser,spatter in laser additive manufacturing and coarse structure in the sample of arc additive manufacturing.Microstructure and mechanical properties were analyzed to compare the 4043aluminium alloy structures fabricated by arc additive manufacturing and laser-arc hybrid additive manufacturing in this paper.And the influence of microstructure on the mechanical properties was analyzed.Main research contents and conclusions are as follows:(1)Selecting appropriate process parameters,including arc current and other arc parameters,laser power and pulse frequency and other laser process parameters,overlap ratio,and so on.Aluminum alloy structures were fabricated by laser-arc hybrid additive manufacturing,in order to prepare for the subsequent microstructure analysis and mechanical properties testing.(2)The evolution of the microstructure was analyzed.And the influence of laser energy and scanning strategies on microstructure(grain morphology,size,growth direction and preferred orientation),element distribution and phase composition were analyzed,which were also compared with the arc additive manufacturing.It is found that when the laser power density reaches 10~6 W/cm~2~10~7 W/cm~2,the microstructural characteristics of the laser-arc hybrid additive manufacturing samples are significantly different from those of the arc additive manufacturing samples.The heat affected zone of laser-arc hybrid additive manufacturing samples decreases,and the grain size in laser zone is refined.Meanwhile the distribution of Al and Si elements in laser zone is more uniform.When using the scanning strategy with crossing direction between adjacent layers,the orientation of grain growth changes,and XRD results show that the preferred orientation of grain changes.(3)The micro-hardness and mechanical properties were evaluated.The results show that the average micro-hardness of laser-arc hybrid additive manufacturing samples is larger,and the micro-hardness value in the laser zone is significantly higher than that in other areas.The scanning strategy has little effect on the hardness.The relationship between the microstructure and mechanical properties was obtained by analyzing the tensile results combined with the tensile fracture characteristics and the microstructure characteristics of the longitudinal section.It is found that the strength and ductility of the sample are enhanced by the input of laser,and the ductility of the fabricated samples are further enhanced by using the scanning strategy with crossing direction between adjacent layers.