Microstructure And Performance Of Cu-Cr Electrical Contact Composites Sintering By SPS

Electrical contact is the key component in electric products,which play an important role in connecting and breaking circuit.The performance of the material is related to the reliability and service life of the switch directly.Cu-Cr composite combines the excellent electrical conductivity,thermal conductivity and good plasticity of copper with high strength,low current chopping and good arc extinguishing performance of chromium.It is one of the ideal structure-function integration composites.In this paper,the Cu-Cr composites with different Cr contents were prepared by Spark Plasma Sintering(SPS).The properties of the composites such as relative density,Brinell hardness and electrical conductivity and microstructures were measured and observed.Meanwhile,the effect of different Cr contents on microstructures and properties of the composites was analyzed.The hot simulation compression tests of the composites were conducted at deformation temperature in the range of 650~950 °C and strain rate in the range of 0.001~10s-1with the Gleeble-1500 D thermal-mechanical simulation test machine.The true stress-strain curves of the material were analyzed.According to the model of hyperbolic function,the thermal activation energy(Q)of the material and the constitutive equation of the flow stress were established,and its accuracy was tested with different methods.Based on the dynamic material model,the processing maps of the composites were obtained.Meanwhile,the best processing range of the composite was determined.The electrical contact experiments were carried out by a JF04 C electric contact test system under the DC condition.The loss and transfer mass of the composites under the condition of different current were analyzed.The ablation morphologies of the composites were observed.In the meantime,the mechanism of arc erosion was discussed in brief.Finally,the experimental parameters such as arcing time,arcing energy,welding force and contact resistance were investigated.The results show as follows:1.The three kinds of the composites prepared by SPS,and the composites were dense and homogenous in microstructure.Cr particles playing the role of reinforcing phase were dispersed in the copper matrix.Relative density,electrical conductivity and Brinell hardness of the composites are 94.3%~97.7%,39.0%IACS ~59.2 %IACS and63.3~72.4HBS,respectively.The density and conductivity of the material aredecreased with the Cr increasing contents,and the Brinell hardness improves.2.The true stress-strain curves of the composites show typical characteristics of dynamic recovery and dynamic recrystallization,and the peak stress increases with the decreasing temperature and increasing strain rate.According to the experimental data,the thermal deformation activation energy(Q)of the Cu-Cr materials are 260.743KJ/mol,242.336 KJ/mol and 235.573 KJ/mol,respectively.The constitutive equations of the materials were obtained and the reliability is higher.3.The processing maps of the composites were achieved by related experimental data.According to the microstructures,the optimal processing parameters were determined ultimately.4.The degree of mass change of the composites will be aggravated with the current increasing.When the current is increased to 30 A,the material is transferred from cathode to anode,and the transfer of contact material will increase with the increasing current.There were ablation morphology such as pores,melting pools and pits presented on the surface of the composites.There was a positive correlation between the arcing time and arcing energy.With the increased testing number,there was no obvious change between the contact resistance and welding force.The contact resistance gradually decreased with the increasing current,and the welding force increased with the increasing current intensity to some extent.