The Research On Pressure Welding Of Copper Foil By Thermo-mechanical Coupling From FSW Process

Experimental investigations were carried out using a numerically controlled milling machine to weld ultra-thin copper foils(20μm and 50μm thickness)in this article.Firstly 50μm and 20μm T2 copper foil were adopted.The effect of welding parameters on the welding joints appearance was studied.Furthermore,welds were analyzed by optical microscopy,scanning electron microscopy(EDS),tensile shear tests and micro-hardness.The ultimate maximum shear-load could be achieved up to 175 N with the rotation speed of 800 rpm and the traveling speed of 20mm/min,which should be attributed to optimum heat and pressure.Temperature curves shapes are almost consistent because only rotational speed changes.The peak temperature of condition was approximately 200℃-256.℃The interface bonding mechanism was also expounded and three main influence factors were analyzed in detail respectively.The bonding of the interface between copper foils could be summarized to the following three reasons:(a)plastic deformation of copper foil;(b)shallow diffusion between copper foil interface and(c)dislocation migration.With the rotation speed increasing,interface bonding was observed tighter on other specimens.It is clearly noticeable that the gap is closing,which reveals the reinforcement of the interface bonding.The failure of all samples occurs in the region of the base metal,next to the overlap joint.From a sufficient of experimental data,the micro-hardness of the overlap joint(50μm)would reached to about 80% of base meter,while 50%for HAZ part on the welding parameters(n=800r/min,v=20mm/min,d=0.1mm).In this study,the micro-hardness of copper foil over-lap joint surface present “W” variation.Base on the changing curves,it could be found that the weakest place existed in the HAZ area nearest the weld where the fracture took place in tensile experiments.It was found that the hot pressure welding process has little effect on the corrosion resistance of copper foil with salt spray test.The experiment provides a feasible solution for the welding of ultra-thin copper foil.