Laser Welding Of CF/PEEK And Micro-textured Magnesium Allo

Automobile lightweighting is an effective way to address energy shortages and environmental degradation.Carbon Fiber Reinforced Polymer(CFRP)is one of the best design materials for lightweighting cars due to its excellent characteristics such as vibration resistance and corrosion resistance.Magnesium alloy,as the lightest metal,is widely used in the manufacturing of automotive components due to its significant strength-to-weight ratio and stiffness-to-weight ratio.The high-quality connection between the two is a key factor in achieving vehicle lightweighting.Laser welding,due to its non-contact,high efficiency,and flexible processing,has become the preferred method for connecting CFRP and magnesium alloy.However,the huge differences in physical parameters such as thermal conductivity and coefficient of thermal expansion between the two,as well as the laser highreflectivity and oxidation sensitivity of magnesium alloy,make it particularly difficult to obtain high-quality CFRP-magnesium alloy heterogeneous material laser welding joints.This article proposes laser swing welding and femtosecond laser surface micro-texturing pretreatment technology for CF/PEEK(Carbon Fiber Reinforced PEEK)composite material and AZ31 B magnesium alloy single lap joint structure,and achieves efficient and highquality connection between AZ31 B and CF/PEEK.Firstly,a finite element simulation model of CF/PEEK and AZ31 B magnesium alloy swing laser direct connection is established,and the reliability of the model is verified by comparing the model calculation results with the experimental results.The temperature field comparison study of swing laser welding and non-swing laser welding processes is carried out,and it is found that swing laser welding can effectively reduce the peak temperature on the surface of AZ31 B magnesium alloy,improve the phenomenon of the rapid rise and fall of the weld temperature and the thermal decomposition of the CF/PEEK resin caused by the concentrated temperature distribution of the joint interface under non-swing laser welding.Therefore,swing laser welding is selected as the process research object.By studying the influence of swing laser welding process parameters on the resin melt depth and width at the joint interface,the optimal process parameter range is preliminarily determined,i.e.laser power of 500W-650 W,welding speed of 5mm/s-8mm/s,swing amplitude of 1.5mm-3.5mm,and initial selection of swing frequency of 40 Hz.Secondly,based on the range of process parameters calculated by the model,laser welding process experiments were carried out.It was found that under the same process parameters,the surface weld quality and joint mechanical performance of oscillating laser welding were better than those of non-oscillating laser welding,which further confirmed the superiority of oscillating laser welding in connecting CF/PEEK-AZ31 B magnesium alloy.The influence of oscillating laser process parameters on the surface weld formation and joint mechanical properties was studied,and it was found that a good weld could be obtained within the calculated parameter range based on the temperature field model.The joint shear and tensile forces increased first and then decreased with the increase of laser power,welding speed,and oscillation amplitude.The process parameters were optimized using response surface methodology(RSM),with laser power of 571 W,welding speed of 6.4mm/s,and oscillation amplitude of 2.3mm,and the resulting joint shear force was 1763 N.Analysis of the interface and cross-section morphology and element distribution revealed that the CF/PEEK and AZ31 B magnesium alloy were mainly bonded by mechanical anchoring effects,van der Waals forces,and chemical bonding.Finally,in order to enhance the bonding at the joint interface,femtosecond laser point lattice micro-texturing pretreatment was performed on the surface of the AZ31 B magnesium alloy,and the influence of micro-texture size parameters on the joint mechanical properties and interface bonding mechanism was studied.Through single-factor experiments and orthogonal experiments,it was found that the joint shear force increased first and then decreased with the increase of hole diameter,hole spacing,and number of repeated processing,and the optimal point lattice structure parameter combination was: hole diameter of 1.2mm,hole spacing of 0.2mm,and 8 repetitions,resulting in a joint shear force of 4345 N,which was 146% higher than that of the joint without point lattice micro-texturing pretreatment on the surface of the AZ31 B magnesium alloy.Analysis of the microstructure and element distribution of the joint interface and cross-section showed that the melted resin filled the micro-texture holes,enhancing the interface mechanical anchoring effect;Mg and C elements inter-diffused at the hole and interface junctions,indicating good physical intersolubility and new chemical bonds.The point lattice micro-texturing pretreatment improved the wettability of the surface of the AZ31 B magnesium alloy,promoting the formation of bonding between CF/PEEK and AZ31B.