| With the development of society,energy saving is becoming more important.Lightweight is an important means to reduce energy consumption and dissimilar metal materials connection is an effective way of lightweight.Aluminum alloy is the second largest metal material in China’s industrial construction system.Because of its low density and good conductivity,it is usually made into composite connector with copper,which is used in the power transportation industry and new energy automobile industry.In this paper,the magnetic pulse welding technology was used to weld the aluminum copper plate.The numerical simulation was used to simulate the welding process and the changes of collision velocity,collision angle and maximum current density were studied.The tensile test and microscopic interface observation were carried out to analyze the difference of the joints with different parameters and the formation mechanism of microscopic interface.The specific research contents are as follows:Firstly,the process of the magnetic pulse welding was simulated by LS-DYNA.The finite element and the boundary element method were used in the numerical simulation.The differences of collision velocity,collision angle and maximum current density under different energy and different flyer plate conditions were analyzed and compared.Although the conductivity of Cu was larger than that of Al,Cu had larger density and larger density than Cu,which required more energy when the collision velocity reached the same.Therefore,Al had a higher collision speed than Cu at the same discharge energy.Secondly,in this paper,the experiment of Al-Cu magnetic pulse welding was carried out and the Al/Cu joints(Al as flyer plate material)and Cu/Al joints(Cu as flyer plate material)were formed under the suitable discharge energy.When Al and Cu were used as flyer plate respectively,the impact velocity was measured by photon Doppler velocimetry measurement system(PDV).The error between the measured impact velocity and the impact velocity of numerical simulation was less than 5%.The mechanical properties of welded joint were explored by tensile tests.The results showed that the maximum tensile load of Al/Cu joint was higher than that of Cu/Al joint under the same discharge energy.When the flyer material was the same,the strength of welded joint increased with the discharge energy increased.When the discharge energy was appropriate,the strength of Al/Cu joint was higher than that of base metal material.The magnetic pulse welding process window was established by collision angle and collision velocity.The welding conditions for forming joints were compared when different materials were used as flyer plate.The microstructure observation of Al/Cu joints and Cu/Al joints was analyzed.The hardness test was carried out on the welding interface with a microhardness tester.It was found that the hardness value of the welding area was increased compared with the hardness value of the original plate metal.The hardness value of the material also increased when the discharge energy increased.Finally,the welding interface was simulated by smooth particle hydrodynamics(SPH)and the temperature distribution at the welding interface was analyzed in the simulation.The results showed that the temperature transfer layer of the interface was asymmetrical along the vertical to the welding contact surface.According to the interface observation by SEM,the wave interface would appear at the contact interface of Al/Cu joint and Cu/Al joint when the discharge energy is appropriate.The regular waveform was more likely to appear in the Al/Cu joint than in Cu/Al joint with the same discharge energy.The orientation of interface wave in Al/Cu joint and Cu/Al joint was revealed to the material density.When using low density metal as flying plate,the orientation of interface wave was the same as the welding direction.When using high density metal as flying plate,the orientation of interface wave was opposite to the welding direction. |
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