Basic Research On Spray Forming Process Of Bimetallic Gradient Composite Board

Hypereutectic Al-Si alloy has the lower thermal expansion coefficient, good thermal conductivity, light weight and superior mechanical properties.It is widely used in the field of aviation, spaceindustry and other high technology as electronic packaging material.It is development has broad prospects. However, when the silicon content is high, mechanical propert y and welding performance are still relatively poor even with the spray forming process. It is also very difficult to solve the requirements of differences in performance between the side wall and the top. In this paper, the contradiction between thermal conductivity, welding and mechanical processing are solved by usin g the gradient of Si component.This paper attempts to study on the spray forming process of bimetallic gradient composite board. Shape model and heat transfer model of the spray forming bimetallic gradient composite board are established by use of the simulation calculation software ANSYS "birth and death" and the APDL programming language. Research on the influence of deposition board shape and composition distribution by different tracking movement, forward speed, swing cycle and the spray center distance. And research on the different process of deposition board temperature distribution affects. Through simulation results, the equipment parameters are determined in order to achieve the predetermined requirements. The accuracy of the simulation results was verified by the experiments.The results show that the surface of the board is smooth and the thickness is uniform. The shape of the deposition broad is from the flat platform to the stepped shape, when the center distance of the atomization cone is increased in the range of 0.02-0.05 m.And the thickness of the gradient distribution becomes more obvious, the width of the transition zone decreases gradually. According to the results, the deposition broad is mainly influenced by the swing period. With the period of oscillation increases(1-8s), composition of each layer by the uniform distribution gradually fluctuate(4 s), finally each layer composition not only uneven and jagged fluctuations; it has no effect on component in the direction of thickness distribution trend, but also can lead to components appear jagged wave dynamic.when the substrate without preheating process t he first deposition part lose a lot of heat and cooling velocity is high.They are not conducive to the atomized droplet with substrate binding. After the substrate preheating, it is beneficial to combine the atomization droplets with the substrate, and the overall temperature of the deposition broad is small, so it has no effect on the solidification of the deposition broad. The temperature control of the craft, which is not only good with the substrate, but also prevents the grain to grow and beneficial to Si solution. However, it is difficult to control the process, and the process is not easy to achieve.The experimental results show that the shape of the board is in good agreement with the simulation results. The mixture of atomi zation droplets in the transition region is not uniform, and we can observe the boundaries of the two components. But the distribution trend of the components in the transition region is basically the same as the simulation results.