Dissertation > Industrial Technology > General industrial technology > Materials science and engineering > Composite materials > Metal composite materials

The Production and Reinforcement of High-performace Copper-based Electrical Contact Composite

Author GuoZhongQuan
Tutor GengHaoRan
School Shandong University
Course Materials Processing Engineering
Keywords Carbon nanotubes Copper-based Composite materials Electrical contact materials High - energy ball milling The surface of the material Arc erosion Conductivity Strengthening mechanism Anti-welding properties Spark Plasma Sintering nanotubes Process Preparation Sintering temperature Mechanical properties Powder Carbon nanotubes Rare Earth Electrical contact performance A metal film
Type PhD thesis
Year 2011
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Switch appliances, electrical contact materials directly responsible for segmentation and connected to the circuit, carrying the normal operating current carrying overload current or within a certain time. The key features of a variety of electrical and breaking capacity, such as electrical power distribution, the reliability of the relay and so depends on the pros and cons of the electrical contact material quality and performance. The most widely used low-voltage electrical silver-based electrical contact material, but silver prices are expensive, the cost is higher. Copper has good electrical conductivity and thermal conductivity, but the lower the hardness and melting point of copper, electrical erosion and welding tendency is more severe, and the copper surface is easy to form an oxide film, and seriously affect the conductive properties of the material. Therefore, this paper attempts to powder metallurgy method, by adding different elements, the preparation of a new type of low-voltage electrical contact with the copper-based electrical composite materials to improve the mechanical properties of the copper-based electrical contact materials, oxidation resistance, arc erosion and anti-welding performance alternative to silver-based materials to reduce costs, save precious metals silver purpose. The paper first discusses the relationship between the Add-phase physical properties and organizational structure of the composite electrical contact performance, and to optimize the design principles of the material composition. The study found that the lower the melting point of the low melting point component material component performance requirements, the greater the evaporation and latent heat of vaporization, the better anti-welding properties of the material; high hardness, high melting point should try to choose the material specific heat, m.p. melting latent heat, boiling point, the latent heat of vaporization, sublimation Add phase of the physical properties such as higher temperature, the conducive material to maintain a stable state; premise does not affect the performance of the material, to add a greater volume fraction, the smaller the particle size, shape The more complex the appearance, the greater the viscosity, the greater the binding force between the metal and adding phase particles, the better the wettability, the greater the viscosity of the composite material, and more conducive to improve the electrical contact properties of the material. Papers according to the requirements of the low melting point component of the physical properties of selected several low melting point of Sn, Bi, Sb, Zn, and to explore its impact on the overall performance of the composite material. The results showed that adding 2 wt% of Bi can effectively improve the arc erosion resistance and oxidation resistance of the material and the conductive properties of the material to meet the requirements of the electrical contact materials. The papers on the Bi-added copper-based electrical contact material the thermal conductivity of the welding region of the finite element simulation, the study found that the Bi add material, the temperature of the welding region conduction easier outwardly, so as to relieve the high pressure of the high-temperature region. The paper ultimately determine the low melting point component was added Bi, the best content to 2 wt%. Papers Fe3Al TiAl added as the hard phase of the different component of the copper-based electrical contact materials, mechanical properties, electrical properties and anti-welding properties. Experimental results show that adding an appropriate amount of Fe3Al, and its uniform distribution in a matrix capable dispersion strengthening role effectively improve the mechanical properties of the material; at the same time during the working temperature Fe3Al, Al capable priority oxide in the matrix is ??formed with a dense layer of A1203, thereby hinder the further diffusion of the oxygen atoms in the matrix to improve the oxidation resistance of the material; Fe3Al itself has good electrical conductivity, in reinforced composite mechanical properties and oxidation resistance, better ensure that the conductive properties of the material, the paper established Fe3Al amount of material oxidation resistance and electrical conductivity mathematical relationship, and ultimately determine the high hardness, high melting point of the optimum phase Fe3Al best content to 2 wt%. The paper attempts to add carbon nanotubes as a reinforcing phase to improve the overall performance of the material in the copper matrix composites. Carbon nanotubes' dissertation">Carbon nanotubes as reinforcing the need to solve two problems: First, the problem of poor performance and the substrate with carbon nanotubes reunion. The first carbon nanotube surface coating process, the carbon nanotubes copper interface combined with improved combination of metal-metal interface, effectively enhance the binding properties of carbon nanotubes with copper substrate, and improve the carbon nanotubes in the matrix by a high-energy ball milling process agglomeration. Paper orthogonal test as a means to discuss the amount of carbon nanotubes to join and surface processing time composite conductive properties, mechanical properties, and anti-welding properties of copper-based electrical contact, and ultimately determine the carbon nanotubes added in an amount of 0.1 wt%, the best high-energy ball milling time 8h, the best surface processing time for 1h. The study found nickel plated and high energy ball milling process, the addition level of 0.1 wt% carbon nanotubes, which can be uniformly distributed in the matrix and effective combination with the matrix to improve the mechanical properties of the material and friction and wear properties. When the addition amount is too high, agglomeration appears in the matrix, the free electron scattering increases, the increase in resistivity, the material density drops. The paper, based on the mechanism of carbon nanotubes reinforced copper composite material in-depth analysis and mathematical model was established aL = σf (1 lc/2l) Vf sigma (1-Vf), the study found that when the long diameter of the carbon nanotubes than l. / D greater than 60 can play a role in strengthening the matrix, and the failure of the carbon nanotubes mainly ductile fracture. Add the right amount of carbon nanotubes in the material as well as help to improve the resistance of the material arc erosion performance, papers doped carbon nanotubes copper-based electrical contact materials welding area finite element analysis, the results of the analysis found that carbon nanotubes introduced making it easier for heat introduced by the carbon tube channel pass out, thereby improving the resistance of the material arc erosion performance. Copper-based electrical contact material can not be the practical application of the biggest obstacle is easily oxidized copper surface, the research found that adding rare earth elements to purify the grain boundaries in copper, grain refinement and improve oxidation resistance. The paper attempts to copper was added in rare earth La La-Cu master alloys and LA203 two different forms, and to explore its impact on the overall performance of the material, especially oxidation resistance. Firstly prepared La content of La-Cu master alloy powder and its morphology characterization and composition analysis. The study found that the La content is 0.4wt% La-Cu intermediate alloy particles uniform, less impurities, and La mainly evenly distributed over the surface of the copper matrix form LA203. Decided La 0.4wt% La-Cu master alloys as add-phase. The paper explores the in-depth the impact of different levels of La-Cu master alloy and LA203 overall performance of the material. The study found that adding the right amount of rare earth - the middle of the copper alloy and LA203 can effectively improve the mechanical properties of the material and arc erosion resistance, the added amount is too high, the conductive properties of the material decline. Test depth study of rare earth different relative oxidation resistance of materials, the study found below 600 ° C La-Cu intermediate alloy adding appropriate amount of inhibition of the oxidation of copper matrix composites is the most obvious, at 800 ° C high temperature oxidation state, LA203 better inhibition of the oxidation of the Cu matrix composites. The LA203-depth analysis of anti-oxidation mechanism, and the establishment of a copper-based electrical contact material copper matrix composites to add a the LA203 second phase particles average surface diffusion expression: J = (?), Obtained by calculating the diffusion flux relationship with the oxidation temperature and oxidation time, the study found the LA203 with its unique structure and physical properties, the initial oxide in the composite material can procure the material substrate to generate a layer of a dense oxide film on its surface, thereby effectively suppressing the surface oxidation of copper-based materials further deterioration. The paper examines the spark plasma sintering process on the material properties and mechanisms were analyzed. The paper first discusses the spark plasma sintering process parameters: the initial pressure, Paul pressure and sintering temperature on the material properties. The study found that the initial pressure is lower, the higher the density and electrical conductivity material, and to determine the the SPS process optimum initial pressure for 5 MPa; dwell pressure and the density and conductivity of the material is proportional to the relationship, the optimum packing pressure is 50MPa ; density and conductivity of the sample with the increase of sintering temperature increased with the increase trend, mainly due to the sintering temperature is too high lead to grain growth, increased porosity, thus affecting the overall performance of materials, research determine the SPS process sintering temperature of 500 ° C. Experiment to determine the optimal parameters of the spark plasma sintering under the premise, comparative study of the ordinary sintering and SPS and the impact on the material properties. SPS sintering process in a shorter sintering time (several minutes) and a lower sintering temperature (500 ° C), rely on the pulse current effective grain refinement, purifying the grain boundary material, in varying degrees, to improve density, hardness and electrical conductivity.

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