An Experimental Study On Laser Scanning Welding Of 2060Al-Li Alloy With Filler Wire

Aluminum lithium alloy has been widely used in the field of aerospace because of its excellent physical properties,therefore,there is the highly standard of the reliability of Al-Li alloy welding.However,at present,there are still many problems to be solved,such as porosity,cracks and low tensile strength after welding.In view of the above problems,a method of "?" shaped laser scanning welding with filler wire was proposed.Taking 2060 Al-Li Alloy with2 mm thick as research objects,the suppression effect of laser scanning welding with filler wire on welding defects of Al-Li alloy was investigated,which could provide experimental basis and guidance for high-quality welding of aluminum lithium alloy.Firstly,a high-speed camera system was built to explore the mechanism and the change of the dynamic evolution of the molten pool.The static and dynamic characteristics of the molten pool were analyzed in order to reveal the eruption rules of the keyhole in the molten pool.The results showed that the dynamic behavior of molten pool is more stable in the process of laser scanning welding with filler wire,when compared to that of in the process of single pass laser welding with filler wire.And the eruption of keyhole shows periodicity with the lower intensity.Where after,the influence of the variation of scanning process parameters(scanning amplitude,scanning frequency)on the weld morphology were explored.Secondly,the weld appearance was evaluated and the basis for selecting process parameters was given.At the same time,the influence of scanning process parameters on the formation of porosity in weld seam and the mechanism of inhibiting porosity of laser scanning welding with filler wire technique were investigated,and the test result shows that the appropriate increase of scanning parameters can effectively inhibit the porosity of the weld.And then,the influence of welding process parameters(laser power,welding speed and wire feeding speed)on the crack formation of Al-Li alloy weld was studied.According to the mechanism of weld crack formation,the inhibition effect of these three parameters on weld crack formation were analyzed,and based on this result,the suitable option of parameters was given in order to suppress the defect of crack.where after,the formation and distribution of microstructure of Al-Li alloy weld were studied.Compared with the process of single pass laser welding with filler wire,the process of laser scanning welding with filler wire have the function to refine the weld grain,and could obtain a narrower equiaxed zone and dendrite zone.Meanwhile,the influence of the combination of process parameters on the tensile strength of weld was studied by using the statistical method of Response Surface Methodology.And the quantitative relationship between process parameter combination and tensile strength,as well as the optimal parameter combination were proposed.The maximum tensile strength of the weld under the optimal parameter combination can reach 381.7 MPa,which is 76.34% of the base metal.At the same time,the microstructure hardness of the weld was analyzed,and verifying that the weld near the fusion line is the weak area,which is easy to fracture.In conclusion,the technique of laser scanning welding with filler wire can effectively suppress the defects of weld porosity and crack,and improve the weld quality.