Research On Integrative Process Of Vacuum Brazing And Heat-Treating For Al₂O₃ Dispersion-strengthen Copper And CuNiSi Alloy

Based on the welding and heat-treatment properties of Al₂O_3p/Cu and CuNiSi alloy and the development of some electrode material, the influence of various brazing process parameters on joint organization performance is studied in this paper, using a vacuum brazing and heat treatment integration process, achieving a high strengthen connection of Al₂O_3p/Cu and CuNiSi alloy, completing the solid solution aging treatment of CuNiSi alloy, to restore the mechanical and conductive properties of CuNiSi alloy. Through the methods such as tensile test in ambient temperature, optical microscopy, SEM and EDS, conductive rate and hardness test, and so on, the study is done.Ag-Cu-Ti filler metal has good wetting to both of the two base metal. Based on Ag-Cu-Ti filler metal, the influence of brazing temperature, holding time, vacuum degree on joint organization performance is studied. It shows that: (1) when brazing temperature is too low, or holding time is too short, the capillary infiltration and diffusion effect from brazing filler metal to base metal is not obvious, and the metallurgical effect is not strong, and the joint organization performance is not good. With the raise of brazing temperature or the extending of holding time, the diffusion effect from brazing filler metal to base metal is full enough, and the ideal joints can be gotten. But the further raise of brazing temperature or extending of holding time, the elements of brazing filler metal severely capillary infiltrate and diffuse to the two sides of base metal, causing no enough elements in joint to fill brazing seam, then holes appear, which seriously affected the quality of joint. At the optimized process parameters, the tensile strength of joint can reach 300MPa. (2) At the same process parameters, the joint organization performance in lower vacuum condition is worse than it in higher vacuum condition, the lower vacuum degree makes the Ti part in brazing filler metal be oxidized, which severely reduces the quality of joint.In order to reduce the Ti content in Ag-Cu-Ti filler metal, add BAg72Cu eutectic filler metal composite brazing filler metal to Ag-Cu-Ti. Comparing the influence of holding time on the performance of two joints at the same process parameters, it shows that when holding time is less than 30 min, the joint performance brazing by Ag-Cu-Ti filler metal is better than brazing by composite filler metal. When holding time is more than 30 min, the joint performance brazing by composite filler metal is much better, so it is good for getting ideal joint by reducing the Ti content in Ag-Cu-Ti filler metal.Imposing certain pressure in brazing will make brazing joint organizations density. The trends of influence of holding time on joint organization performance keep consistent with no pressure. When holding time is relatively short, the performance between pressured joint and unpressured joint has no much difference. When further extending holding time, the brazing seam of the pressured joint becomes narrow, the capillary effect in it becomes strengthen, the seam organization is still density, the joint organization performance is better than it is at the same process parameters without pressure. The tensile strength of joint can still reach 300MPa when the holding time is 40 min.After brazing aging treatment, the conductive rate and hardness of CuNiSi alloy has greatly increased. The hardness reaches 207 HV50, the aging treatment has no big effect on the joint performance. With the raise of quenching temperature, the conductive rate of CuNiSi alloy slightly declines; but the hardness of it is obviously improved.