Study On Continuous Drive Friction Welding Process And Properties Of Cu/Al Materials

In this paper, aluminum and copper dissimilar materials were joined by continuous drive friction welding process. To determine the proper friction welding process parameters, the microstructure, mechanical properties, conductivity and corrosion resistance of aluminum and copper dissimilar materials were investigated by optical microscope, scanning electron microscope, x-ray diffraction, tensile test, bending test, hardness test, eddy current conductivity instrument and corrosion test. This study has got some conclusions as follows.The influence of the continuous drive friction welding parameters on microstructure and properties of aluminum and copper dissimilar materials specimens were studied. When the spindle speed is 200r/min, the friction time is 6s, upset pressure is 400 MPa, the joint interface of aluminum and copper has good mechanical properties. When friction welding specimens of aluminum and copper was bended at 90° at room temperature, there is no crack between joint interface, aluminum and copper combination is good, so the bonding strength of copper and aluminum combination is higher than industrial pure aluminum. The tensile test results friction welding specimens of aluminum and copper show that the specimens are tensile fracture in aluminum side; aluminum side produces the larger uniform deformation, the weld region have a higher ultimate tensile strength than the parent aluminum. When friction welding specimens of aluminum and copper within 25 mm diameter were compressed 8mm thick plate at room temperature, the joint interface of aluminum and copper is good, there is no cracking; the friction welding specimens has good cold forming performance. The compression press test results show that the conductivity of welded bonding is between the conductivity of copper and aluminum, so it can meet the application requirements of electric power industry. The microstructures of friction welding specimen center area showed that the microstructures are combining with the serrated and a flat, the copper substrate of interface region exhibits fine copper grain size; in the surface area of friction welding specimen, the copper substrate of interface region exhibits an irregular copper grain and the grains of aluminum are elongated along the rolling direction.The effects of heat treatment temperature on microstructure and properties of continuous drive friction welding of aluminum and copper materials has been investigated, and the heat treatment temperature are 200℃, 300℃, 400℃and 500 respectively. The results show that ℃when the temperature of heat treatment is 300℃, the welding interface of aluminum and copper generates a thin discontinuous diffusion layer, and the conductivity of welded bonding improves from 75% to 77%. Then the electrical conductivity decreases with the increasing of temperature. The bending test showed that when the heat treatment temperature is 400℃ and the bending angle is 35°, the cracks appeared in welded bonding of aluminum and copper.The corrosion resistance is studied by immersion test with 0.5%NaCl, 3.5%NaCl and 5%NaCl solution, and the corrosion time are 24 h, 48 h, 96 h, 168 h and 336 h respectively. The results show that the corrosion rate of welding specimens of aluminum and copper is about 0.2g / m2·h for 3.5%NaCl solution when the corrosion time is 24 h, while the corrosion rate are all the highest for 0.5%NaCl, 3.5%NaCl and 5%NaCl solution when the corrosion time is 96 h. With the corrosion time increasing, the number of corrosion pits in aluminum side increases and the size of the pits are larger and larger.