Welding Microstructure and Joint Structure Design of the TC4/Ni Dewar Cold Finger

The brazing process of TC4/Ni for a Dewar cold finger with a miniature Joule–Thomson-cooled infrared focal plane detector was selected, and the brazing process of TC4/Ni was investigated based on the microstructure of the brazing method and solder type and the reliability of the joint structure. The results show that research on the brazing process of the TC4 /Ni cold finger end-face structure has practical significance in engineering by combining the simulation results of stress, deformation, and cooling time with the analysis results of rust prevention and corrosion. Through an orthogonal test, an improved process scheme of the high-temperature vacuum brazing + AgCu28 brazing filler metal combination was determined, which could control element segregation and reduce the formation of the welding brittle phase. Based on the penetration rate, stamping, high-voltage holding, and shear strength tests, the conical weld was the best welding structure.