| Ag has often been used as interconnector of solar cell array in space flight due to its excellent toughness, conductivity and good weld ability. But its ability that withstands space environment in Low Earth orbit(LEO) is insufficient; it can't meet the requirements of long-term in-orbit service for space vehicle. Mo/Ag series laminar metal matrix composites which has low thermal expansion coefficient, excellent heat shock, conductivity and weld ability, et al, and has the resistance for atomic oxygen(AO) and no magnetic is very suitable for the LEO spacecraft.In previous work, the research group has put forward a kind of "no solid solution alloying metal irradiation damage mechanism" to solve the problem of the layered composite of Mo/Ag. But that method is with the low production efficiency and high requirements for equipment. In order to solve this problem, this paper added Pt interlayer between Mo-Ag to prepare the Mo/Pt/Ag series laminar metal matrix composites.This process is simple and reliable with high production efficiency, which is suitable for mass production.We obtained the following results:(1) The combination process of calender with several times and heat treatment under gas protection can solve the surfactant deficiency problem of Mo, promote the diffusion alloying of Mo-Pt and Pt-Ag and improve the interfacial strength of the layered composite materials. The combination process of double pulse plating of Ag and the calender can make the quality of the microstructure close to the effect of vacuum deposited Ag. Based on the above, this paper solves the intensity uniformity and stability of resistance spot between the Mo/Pt/Ag layered composite materials and space solar cells;(2) That composite materials have been applicable to the actual model, the highest stretch combining strength by resistance spot welding between Mo/Pt/Ag layered metal matrix composites and spacecraft solar cells can over 582 gf with an average of 376.4gf, which meet national army standard GJB2602-1996 and 160 gf of space requirements raised by users. This paper discussed in detail the factors of interface strength, including calender force, the number of calender, annealing temperature, holding time, plating methods;(3) This paper study interfacial layers of Mo/Pt/Ag metal matrix composites and microstructure of the matrix by high-resolution and general transmission electron microscopy(TEM). Mo metal lattice is normal, and form MoPt and Mo3 Pt with Pt at interface, obtaining a metallurgical bond. Annealing twins were formed at the surface layer Ag, which also confirmed twin plane and way of annealing twins.(4) Finite element simulation of resistance spot welding process of Mo/Ag layered metal matrix composites and space GaAs solar cells reveals the regularities of formation of nugget, obtained temperature field distribution under transient conditions, which is of great guiding significance to develop the resistance spot welding specification between the composite and solar cells. |
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