Effect Of Laser Composite Processing On Surface Microstructure And Properties Of Cu-Cr Alloy

Cu-Cr alloy is widely used in the high pressure electric power systems due to its high strength and hardness, good thermal conductivity and electrical conductivity, strong corrosion resistance. The new contactor materials which have better properties than Cu-Cr alloy have not been found, so Cu-Cr alloy has caused wide concern and research interest of the materials industry. Reducing the content of Cr and improving the properties of Cu-Cr alloy to meet the requirements of contactor materials are the trend of the times with the development of modern science and technology. Laser shock processing (LSP) which is known as"the Common processing method of the manufacturing system in the future", is a new technique for improving metal surface mechanical properties by the high amplitude shockwave induced by the laser. In this paper, the deformation and aging treatment are used for Cu-Cr0.9 alloy, and then the LSP ia used for the surface strengthening. Mechanical properties and electrical properties of the alloy are measured before and after the LSP. The effect of the deformation, aging temperature, aging time on the properties of the alloy is studied and the microstructures and properties after the LSP are also analyzed.The results show that after aging the hardness of the alloy is increased with the deformation increasing and the conductivity has little change. When the deformation reaches 40%, the hardness increases slightly and has a downward trend. The exhalation power of the Cr phase is not enough when the aging temperature is too low. Many small Cr exudates are dissolved out in the matrix with the temperature rising. As a result, the substrate is strengthened and the conductivity is improved. The best aging temperature is about 475℃. With the temperature increasing, the grain is coarsening and the mechanics properties declined sharply. Because the aging exhalation is a slow process, the short time causes inadequate exhalation; the long time can make the grain continue to grow up, so the precipitation strengthening effect is reduced. Therefore, the appropriate aging time is 4h. A lot of dislocations and twin structures are produced in the alloy after the LSP and then contribute to the dislocations pile-up. The original coarse grains are subdivided into different subgrains, so the grain boundaries are refined. The existence of twin structures can improve the strength of the materials and meanwhile it has no significant effect on the conductivity. Therefore, the properties of the alloy are increased greatly after the deformation, aging and LSP. The microhardness increases by 127.7% from 68.7HV after solution to 146.4HV after LSP and correspondingly, the conductivity increases by 66.6% from 53.6% IACS to 89.3% IACS.