Microstructure And Properties Of Silver Tin Oxide Electrical Contact Materials

The differences of the micro structure and properities of the bulk sinters, between the fabrication methed of powder metallurgy and reactive synthesis for silver tin oxide composite, are studied in prensent thesis. With the increase of the tin oxide content in silver matix, the electric conductivity of the composite tended to decreace. While in the same tin oxide content, the electric conductivty of the composite fabricated by reactive synthesisis better than that by powder metallurgy. One of the reasons is that the regular net structure existing in former composite. Due to the unorderly microstructure and the tin oxide assemble in matrix, the electric conductivity of composite fabricated by powder metallurgy became lower than that composite fabricated by reactive synthesis. Moreover, the erosion resistance of the composite by reactive synthesis is also superior to another. Due to better combination, the laser scan made the melt Ag held in play by tin oxide not to be escaped from the materials. Furthermore, the net microstructure in composite also increases the erosion resistance.In the process of the tensile experiments of the wires , the materials that made from reactive synthesis, the initial strength and hardness is lower than that of the powder metallurgy, and then the tensile strength increased quickly with the elongation increase. The abnormality of the hardness and elongation apeared when prolongation of the composite made by in-situ reactive synthesis is 7-26%. The hardness and prolongation reach to the extrema , while the better working performance of the composite can be obtained. When the prolongation is 16%.The particle of the materials that made from reactive synthesis are finer, which assemble from the nanocrystalline. Due to the bad combination of silver and tin oxide made by powder metallurgy, only thick grains of the silver was observed in the electron microcope. Anyhow, because of its advanced production way, the fabrication method of reactive synthesis presents the great advantage in the aspect of the structure of the materials , and can become the new technique of preparition .