Finite Element Simulation Of Cumulative Extrusion Deformation Of Reactively Synthesized AgCuOSnO₂ Composites

Based on the highly complementary characteristics of AgCuO and Ag SnO₂contact materials,the development of new AgCuOSnO₂ contact materials is one of the prospective way to replace the toxic"universal contact material"Ag Cd O.Materials production includes two stages of billet preparation and processing.Researchers on the preparation of complex-phase oxide-reinforced Ag-based composites have conducted in-depth research,but the processing of AgCuOSnO₂ contact materials,especially the hot extrusion process,has not been reported,even if the processing technology has a substantial impact on the performance.For this reason,based on the AgCuOSnO₂ composites prepared by the reaction synthesis,the influences of the secondary phase particle size,extrusion process(preheating temperature,cone die angle and extrusion speed)to stress,strain and microstructure were explored through MSC Marc finite element analysis.The following conclusions were obtained:Phase,energy spectrum and microstructure analysis show that only three phases of Ag,Cu O and SnO₂ be found in the re-pressed and re-sintered billet;Cu O and SnO₂particles mainly exist in the form of circular clusters and are distributed in a network,in which Cu O particles are dark gray and SnO₂ is light gray,and there are large,medium and small sizes.When investigating the effect of particle size,it was found that as the particle size decreases,the dispersibility of the second phase particles gradually increases,however the possibility of"tailing"of the billet continues to decrease.Besides,cubic-Cu O will evolve to fibrosis,which the degree of fibrosis is increases with the size of the particles and clusters,the middle of the billet>the front part>the end and the surface layer is stronger than the core.Furthermore,many Cu O fibers will be bent,and the degree of flexion is is positively related to the size of the particles and clusters.Additionally,there are fibrous Cu O inconsistent with the extrusion direction at the front and end part of the billet,and the difference is is negatively related with sizes.When investigating the effect of preheating temperature on the extrusion process,it was obtained that increasing the preheating temperature will cause stress reduction,particle dispersion and better metal fluidity,which will help reduce the depth of mold wear,but will reduce the degree of fiber about cubic-Cu O.The temperature of billet in the axial direction and diameter appears layered,and they show opposite rules as the extrusion progresses.There is an extrusion moment when the temperature difference in the axial direction is basically zero,and increasing the preheating temperature will speed up the arrival of this moment.When investigating the impact of angle on extrusion,it was given that the billet stress and the degree of"tail shrinkage"to decrease firstly and then increase with the squeeze angle increases.At 45°extrusion,the billet has the smallest stress,"shrinkage"and the best dispersibility.At early squeeze(before the entrance of the sizing belt),with the increase of the extrusion angle,both the deformation degree and trend of the second phase particles are greater;but in the late stage of the extrusion,the deformation degree of the second phase is positively related to the extrusion angle.When investigating the influence of the extrusion speed on the extrusion,it was knew that the stress of the AgCuOSnO₂ composites has kept decreasing with the extrusion speed from 1.8 mm/s to 5.8 mm/s,indicating that the billet has entered stress and the strain has decreased.Enhancing the extrusion speed will lead to the strong stress coverage of the enhanced phase to expand,and the axial tensile rate of the oxide particle clusters will increase and then decrease,but the radial compression will continue to decrease.The particle dispersion effect is best at 3.8 mm/s.The microstructure and mechanical properties of the extruded materials show that the structure morphology in the finite element simulation is observed in the actual extruded profile,such as inverted"S"and"C"for Cu O fibers,but there are also not cases were found in finite element simulation.One is that SnO₂ particles will aggregate along the Cu O fibers,however,will basically not exist around the monoclinic-Cu O particles.The second is that a large amount of SnO₂ will also be present where Cu O fibers are about to break or already broken.The resistivity of re-pressed and re-sintered materials decreased by 68.1%,while the hardness increased by only 8.9%,suggesting that the extrusion process helps greatly improve the conductivity of the material and maintain the processing performance of the materials.