Effects Of SnO₂ Content On The Microstructure And Properties Of AgCuOIn₂O₃SnO₂ Electrical Contact Materials

With the electrical contactors becoming more and more precise and miniaturized,the working environment and service conditions become more and more complex and severe,and the single-phase reinforced silver based electrical contact materials have been difficult to meet the high requirements.In recent years,due to the synergistic effect of different oxide reinforced phases on the improvement of microstructure and properties of materials,multi-phase metal oxide reinforced silver based electrical contact materials have become a research hotspot in the field of electrical contact materials.Relevant researches showed that the wettability between CuO,In₂O₃ and Ag is good,which can effectively increase the viscosity of the molten pool system,reduce the splashing loss of materials,and improve the arc erosion resistance of electrical contact materials.SnO₂ is a brittle phase and has poor affinity with Ag.When the molten pool is formed,it will float on the surface of the molten pool,increase the interface brittleness,and then improve the resistance of electrical contact materials to fusion welding.Therefore,in this paper,four kinds of AgCuOIn₂O₃SnO₂electrical contact materials with different SnO₂ content were prepared by reaction synthesis and large plastic deformation process.The effect of SnO₂ content on the structure and properties of AgCuOIn₂O₃SnO₂ electrical contact materials was studied.The results show that the microstructure and properties of AgCuOIn₂O₃ electrical contact materials can be improved by adding proper amount of SnO₂.The theoretical calculation of the formation process of metal oxides shows that during the reaction sintering process,all the alloy elements will undergo spontaneous oxidation,and the oxidation sequence is In→Sn→Cu,and the formed metal oxides can exist stably in the multiphase system.In addition,the diffusion reaction process of the three alloy elements belongs to the same oxidation mechanism,and the generated metal oxides are dispersed on the surface and inside of the alloy particles.The microstructure of AgCuOIn₂O₃SnO₂ electrical contact materials was observed and analyzed.It was found that the metal oxide existed in the silver matrix in the form of ring structure after reaction sintering.After re-pressed and re-sintering,the porosity and other defects in the sample are obviously reduced,and the homogeneity of the structure is improved.Large plastic deformation leads to the dispersion distribution of metal oxide particles,which is linear along the drawing direction.The physical and mechanical properties of AgCuOIn₂O₃SnO₂ electrical contact materials were tested and analyzed.The results show that the increase of density and the decrease of microstructure defects will cause the decrease of resistivity and the increase of hardness.Moreover,with the increase of the plastic deformation,the agglomerated metal oxide particles are gradually dispersed and distributed in the silver matrix,which has a dispersion strengthening effect on the electrical contact materials.The electrical contact performance of AgCuOIn₂O₃SnO₂ electrical contact materials was studied and analyzed.The results show that with the increase of test voltage and current,the average value and fluctuation degree of welding force and contact resistance of the sample increase obviously.Under the action of arc erosion,the material transfers from anode to cathode,and the surface of moving contact（anode）forms pit shape,while the surface of static contact（cathode）shows crest shape.The diameter of molten pool and the amount of material transfer increase with the increase of test voltage and current.According to the analysis of microstructure and properties,when the content of SnO₂ is in the range of 0.5 wt%～1.0 wt%,the AgCuOIn₂O₃SnO₂ electrical contact material has a more uniform microstructure and excellent physical,mechanical and electrical contact properties.Compared with AgCuO（10）In₂O₃（2）electrical contact materials,the agglomeration degree of In₂O₃ particles is significantly reduced,and the homogeneity degree of sample structure is significantly improved,which leads to the effective improvement of the resistance to fusion welding and arc erosion of electrical contact materials.