Research On Pulse Laser Welding Process And Microstructure And Properties Of Al25Si4CuMg High Silicon Aluminum Alloy

High-silicon aluminum alloys are widely used in automobiles,aerospace,and various electronic packaging products due to their light weight,excellent wear resistance,heat resistance,high specific strength,low thermal expansion rate,and excellent mechanical properties.The welding methods of Al-25Si-4Cu-Mg high-silicon aluminum alloy mainly include brazing,argon arc welding,friction stir welding,electron beam welding and laser welding.Because of its high degree of automation,high accuracy,and small joint deformation,laser welding has become the main connection method for Al-25Si-4Cu-Mg and other high-silicon aluminum alloys.Among them,pulse laser welding is another kind of energy output laser welding.Compared with continuous laser welding,its advantages are mainly reflected in the welding heat input is lower,the thermal effect is smaller and the thermal deformation is smaller.However,the research on laser welding of Al-25Si-4Cu-Mg high-silicon aluminum alloy only stays in the process of exploring,and the impact of changes in energy output mode on its weld microstructure and performance needs to be further studied.In this paper,a pulse laser is used to perform a pulse laser self-fusion welding test on a 2mm thick Al-25Si-4Cu-Mg high-silicon aluminum alloy,by discussing different welding process parameters(defocus,peak power,pulse width,pulse frequency,welding speed,etc.)For the influence of welding seam formation,optimize the process parameters to obtain a well-formed pulsed laser welded joint,and then study the microstructure of the pulsed laser welded seam.At the same time,the microstructure and mechanical properties of pulse laser welded joints,pulse laser remelted welded joints and fiber continuous laser welded joints are compared and analyzed in detail.First,by studying different cross sections of the same weld,the following rules are observed: during the change from point a to point d,the sag of the residual high and middle parts of the weld goes from scratch,and the amount of depression increases from small to large.The waist width increases accordingly,but the effective depth of the weld decreases,and there is no significant difference in the amount of depressions on the back of the weld.Next,a pulse laser self-fusion welding test was carried out on the surface of a 2mm thick Al-25Si-4Cu-Mg high-silicon aluminum alloy: the effect of pulse welding process parameters on the weld formation was obtained,and the better process parameters were obtained: defocusing amount + 4mm,Peak power 2600 W,pulse width 12 ms,pulse frequency 18 Hz and welding speed 7mm / s,the optimal weld spot texture is clear,dense and neatly arranged,more beautiful,but there is a small amount of spatter on the back of the weld.Secondly,the microstructure analysis of the pulsed laser welding seam found that due to the difference in the cooling rate of each area of the weld seam,the size of the silicon phase will be different.The size of the upper area of the weld is the smallest,the size of the middle area of the weld is the largest,and the other areas are in the front.Between the two.At the same time,Al2 Cu phase was found to be uniformly distributed in the weld.The microstructures of pulsed laser welds and pulsed laser remelted welds and fiber continuous laser welds are then compared: in the upper,lower and middle regions of the weld,the average size of silicon phase particles and the average spacing of silicon phase particles are from large to small The arrangement order is continuous fiber laser welding seam,pulse laser welding seam and pulse laser remelting welding seam.Fiber continuous laser,pulsed laser,and pulsed laser remelting welds all have Al2 Cu phase,and the grain size decreases sequentially.Next,the mechanical properties of pulse laser welded joints,pulse laser remelted welded joints and fiber continuous laser welded joints are compared: all three can significantly increase the hardness value of the weld zone compared with the base material,and the average hardness of the weld zone increases Large and tensile strength increase sequentially.Finally,the formation of pulse laser welding seam porosity and its porosity and size compared with continuous laser welding seam are compared.It is found that for Al-25Si-4Cu-Mg high-silicon aluminum alloy,pulse laser welding can suppress the generation of pores more than continuous fiber laser.