Cu-al Friction Stir Welding Lap Joint Microstructure Properties And Temperature Field Study

Copper and aluminum can be found a variety of applications in electric power,automotive and refrigeration HVAC industries.However,copper is much more expensive than aluminum.Therefore,by replacing all or part of copper with aluminum components to reduce costs,It is one of the hot spots in the research and engineering application of related industries.The simultaneous application of aluminum and copper will inevitably produce a large number of copper and aluminum joints,and by studying the efficient welding method of aluminum/copper dissimilar materials,obtaining high quality copper/aluminum joints is a challenging task.Friction stir welding is a new type of solid phase welding technology,and lap joints can achieve good dissimilar metal connections for different thickness combinations.The friction stir welding process of aluminum/copper dissimilar metal is still in the stage of experimental research.There are not many reports on the temperature field of aluminum/copper dissimilar lap joints.Studying the friction stir welding temperature field has guiding significance for selecting welding process parameters.In this paper,1060 pure aluminum and T2 pure copper of 2mm thickness are selected as the research object to perform friction stir lap welding.The welding parameters and the diameter of the mixing head's shoulders are used to study the surface formation of the weld,the macroscopic appearance of the weld cross section,and the mechanical properties.The law of influence was explored,and the microstructure and phase composition of copper-aluminum joints were explored.At the same time,the temperature field distribution rule of copper-aluminum friction stir-welded joints and the heat-generating mechanism were studied through thermocouple measurement of temperature field and numerical simulation method.By reasonably setting the rotating speed and the traveling speed of the stirring head,a lap joint with a good welding quality can be obtained.From the cross-section of the weld,the grains in the nuclear area are fine and uniform,and fine copper particles are distributed in the upper layer,and a copper-aluminum mixture is formed in the lower layer.The grains in the heat-affected zone are larger.There are thin,continuous and uniform IMC CuAl₂ and Cu₉Al₄ in copper-aluminum joints.Copper-rich Cu₉Al₄ phase more than aluminum-rich CuAl₂.IMC increase the peak hardness of the weld cross section,and a small number of IMC also increase the bonding strengthThis article uses a thermocouple to measure the temperature of the friction stir lap welding heat process,and obtain the temperature curve of different characteristic points.It is found that during the friction stir welding process,the temperature profiles of the characteristic points have similar trends of temperature increase and decrease trends.In the horizontal position of the same length of the weld,the peak temperature of the back welding is greater than the front position,and the deep peak temperature decreases as the thickness of the plate increases.This paper also uses ABAQUS software to establish a three-dimensional model of the welding process,and have a numerical simulation of the welding heat process.The results show that the temperature at the center of the weld is far below the melting temperature of the metal.Comparing the temperature curves of the simulated feature points and the measured points,it is found that the established model is reasonable and has a good accuracy.Further temperature field experiments show that this heat source has better adaptability in conventional friction stir welding.