Capacitor Discharge Percussion Welding Of Dissimilar Metals With Copper And Aluminum

There are large differences in physical and chemistry properties between copper and aluminum, and kinds of brittle compounds can be engendered in the welding joints. These enormously influence the joint microstructure and mechanical property. In this paper, wires and sheets of copper and aluminum were welded using capacitor discharge percussion welder. Orthogonal experiments were designed to optimize the parameters, and then, tensile strengh of joint, the effects of process parameters, namely capacitance, charging voltage, wire taper angle and machine oil on fracture pull of joint were studied. Microstructure, morphology and ingredient were studied by metallographic microscope, scanning electron microscope and micro-hardness test. The main conclusions are as follows:For the welded copper wire and aluminum sheet, the optimum technological parameters are: C=70mF, U=65V, a=90°, and adding oil. The maximum tensile strength of the joints is 376.24MPa, approaching 97 percent of the tensile strength of copper wire. For the welded aluminum wire and copper sheet, the optimum technological parameters are:C=60mF, U=50V, a=60°, and adding oil. The maximum tensile strength is 163.40MPa, and the fracture happened on aluminum wire, so the tensile strength of the joints was higher than the aluminum wire.Copper and aluminum can form sound welding joint and the heat-affected zone is narrow. The action of percussion squeezes the overmuch melting liquid out, and also reduces the loose and porous joints. After capacitor discharge percussion welding, the microstructure of the joint shows rapid solidification feature, characterizing cellular dendrite mainly in the nugget. And the value of micro-hardness of the joint is higher than that of bilateral basal metal.The process of CDPW included voltaic arc discharging and mechanical movement, and the period is extremely short, about 0.015 second. The relationship between temperature and time in cooling process were analyzed by one-dimensional heat conduction equation, simulated Ray-Karin model. The cooling rate in fusion zone of joints, which was calculated by metallographic analytical method, is more than 105K/s.