Effect Of Oxide Additives On The Mechanical Behaviors Of Ag-SnO₂ Contact Material And Its Mechanism Study

Environment friendly Ag-SnO₂ contact material has received widespread attention in the field of low-voltage electrical appliances due to its excellent electrical contact performance.It is often used as the core component of electrical system to undertake the connection,conduction and disconnection of current.However,the phase interface of the Ag-SnO₂ material is not wetting,the bonding strength is low,and serious stress concentration is likely to occur around the SnO₂ during the deformation process,which leads to processing difficulties.In this paper,the effects of different additives on the mechanical behaviors of Ag-SnO₂ contact material were systematically studied through tensile,cyclic loading,constant stress creep experiments and finite element simulation.The main contents are as follows:(1)Tensile and cyclic loading tests were carried out on the Ag-8wt%SnO₂samples containing different additives.The fracture morphology was observed by scanning electron microscope(SEM),and the fracture mechanism was analyzed.It was found that oxide additives significantly improved the strength limit and uniform elongation of the Ag-SnO₂material.The tensile strength of the sample with Cu₂O was the highest,reaching 134.6 MPa,which was about 61%higher than that of the sample without additives.The CuO additive improved the plasticity and fatigue creep resistance of the material by inhibiting the generation of intergranular cracks.And,the addition of In₂O₃ significantly increased the elongation of Ag-SnO₂ material.When the size of SnO₂ particles was reduced to about 70 nm,the additives didn't significantly improve the mechanical properties of the Ag-8wt%SnO₂ contact material,and even large-size cracks appeared.(2)The mechanical behavior of the Ag-SnO₂ samples containing CuO and Cu₂O under tensile and cyclic loading was systematically studied,and the fracture mechanism was simulated and analyzed by ANSYS software.The results showed that a small amount of CuO and Cu₂O additives had a significant effect on the mechanical properties of Ag-SnO₂ material.The samples containing 0.5 wt%Cu₂O showed the best mechanical properties,and the strength limit and uniform elongation were increased respectively 60%and 21%;copper oxide additives make the Ag-SnO₂material change from brittle fracture to ductile fracture,and large dimples were formed around the SnO₂ particles.At the same time,this type of additive significantly improves the fatigue and creep resistance of the material;during the stretching process,stress concentration occurs around the SnO₂ particles,which leads to the initiation and propagation of cracks.The addition of CuO and Cu₂O could improve the bonding strength of the material interface and correspond to concentration has a certain relief effect.(3)The samples of the Ag-SnO₂ material containing CuO,WO₃ and In₂O₃additives were prepared,and a constant load creep experiment was carried out at room temperature.Based on the obtained experimental results and related parameters,the creep constitutive equation of the Ag-SnO₂ material was constructed.The morphology of the tensile fracture was analyzed by scanning electron microscope(SEM),and the creep behavior was further simulated by ABAQUS finite element software.As the strength of the interface between SnO₂ and Ag matrix was improved,the overall creep and steady-state rate of CuO additive samples under constant load are reduced by 66%and 55%,respectively.At the same time,CuO effectively inhibits the initiation and propagation of cracks.The simulation results were basically consistent with the experimental data,and the error was less than 3%,which verifies the correctness of the model.(4)The thermodynamic properties of Ag-SnO₂ contact material with additions under arc action were numerically simulated by ABAQUS finite element software,and the temperature field and thermal stress distribution of the material under arc heat flow were obtained.According to the simulation results,there was obvious thermal stress around SnO₂,which was similar to the stress concentration phenomenon in the tensile process.The thermal stress depended on the temperature field and the morphology of SnO₂ phase.Oxide additives,especially CuO,could reduce the thermal stress at the interface of Ag matrix.Spherical SnO₂ particles were more beneficial to improving the thermodynamic properties of the material.The results of this paper shows that the CuO and Cu₂O additives can significantly improve the mechanical properties and processing properties of Ag-SnO₂ contact material,which can play a certain guiding role in the processing and performance improvement of Ag-SnO₂ contact material and promote its wide application.