喷射沉积内氧化颗粒增强铜基复合材料的制备及其组织性能研究

【作者】 谢明；

【导师】 史庆南；

【作者基本信息】 昆明理工大学 ， 材料学， 2014， 博士

【摘要】 颗粒增强弥散强化铜材料Cu-Al2O3(Y2O3、SiO2、TiC、SiC、TiN、Si3N4等),是以金属为基体,采用各种金属氧化物、金属间化合物或非金属纤维等作为弥散强化相制备的复合材料,是制做电极、触头、引线、微波管构件及整流转子等的关键材料,广泛应用于电力、电工、电子、机电等行业。目前,国内外Cu-Al2O3材料的制备方法主要有：(1)机械合金化法；(2)粉末内氧化法。前者制备的材料由于A1203颗粒粗大、界面与铜基体的润湿性差,难于成形加工,力学和电学性能不高；而后者制备工艺复杂,A1203颗粒大小和形状不易控制,材料密度低,导致物理、力学性能不稳定。因此,上述方法均不能很好解决A1203在铜基体中界面润湿性差、颗粒粗大、分布不均匀等问题,从而影响到弥散强化铜的综合性能和成品率,限制了Cu-Al2O3复合材料的应用范围。为了改善A1203增强相与铜基体的浸润性及其在铜基体中的大小和分布,最终提高材料的物理、力学和电学性能。本论文提出：(1)采用喷射沉积、内氧化、轧制、拉拔等技术集成,以及在铜铝合金中添加微量稀土元素制备CuAl2O3、 CuAl2O3La2O3y2O3复合材料的创新思路。(2)通过工艺条件、沉积时合金锭坯的显微组织、物理性能、力学和电学性能等之间的关联性研究,获得制备组织晶粒为细小等轴晶粒、无偏析、致密度高、氧化物颗粒细小呈弥散分布的圆柱形合金锭坯的最佳工艺参数(即熔炼温度1300℃、雾化气体压力1.5MPa、开始沉积距离350mm、沉积器转速180deg/s),获得近终成形效果良好,相对密度为94%、沉积效率为87%的锭坯；通过对喷射沉积、雾化液滴的形核、锭坯的显微组织形成过程等的理论研究,建立喷射沉积合金锭坯的显微组织晶粒分布模型。(3)内氧化机理是喷射沉积内氧化制备高性能CuAl2O3、CuAl2O3La2O3Y2O3复合材料的关键技术之一,本论文对其内氧化热力学和动力学条件进行了研究；利用DSC差热分析确定了内氧化过程的温度、时间,考察了不同反应温度、时间对材料显微组织、性能的影响；利用XRD、SEM、HRTEM等测试手段,对合金内氧化前、后的晶格常数和复合材料的组织结构变化及第二相析出颗粒进行了分析,结果表明内氧化生成的A12O3、La2O3、Y2O3颗粒细小、均匀、无偏析,弥散分布于铜基体的晶粒内部和晶界上,与基体的润湿性好、界面干净；内氧化生成的A1203为六方晶系结构,与Cu的错配度(f-74%)>25%,二者为非共格关系；La203为立方晶系结构,与Cu的错配度(f=22%)5%<f=22%<25%,二者为半共格关系；Y203为立方晶系结构,与Cu的错配度(f=3%)<5%,二者为共格关系。(4)通过实验分析和铝元素的沉淀析出量、铝元素在铜中的扩散系数计算及氧化物的生成与形核长大等理论研究,获得第二相氧化物颗粒的形成为扩散控制的抛物线生长机制,在内氧化初期,.A1203颗粒的形成受到Al原子在铜基体晶界上扩散速率控制；在内氧化后期(或高温条件下),A1203颗粒的形成受Al原子在铜基体晶内扩散速率决定等结论。通过计算获得Cu-Al合金中铝在铜中的平衡固溶度变化规律、不同温度条件下过饱和固溶体Al的析出量,以及各反应阶段A1203颗粒大小为0.45～24.51μm,这与CuA10.55合金在980℃、内氧化2.5h后,所得到的样品中氧化物颗粒大小为0.5-20μm的实验结果基本一致。本论文研究了不同变形量10%、30%、50%、70%、90%,对CuAl2O3、 CuAl2O3La2O3Y2O3材料的电导率、硬度、抗拉强度等性能和显微组织的影响；研究了不同退火温度700℃、900℃、980℃对CuAl2O3La2O3y2O3材料的电导率、硬度等性能和显微组织的影响；对材料的强化机理、电阻构成、断口形貌与断裂机理进行了理论分析。获得CuAl2O3材料的密度大于8.7g/cm3,抗拉强度大于450MPa,电导率大于47S/m(导电率>80%IACS)；CuAl2O3La2O3Y2O3材料的密度大于8.7g/cm3,抗拉强度大于500MPa,电导率大于48S/m(导电率>80%IACS);材料的力学性能和电导率等优于其它机械合金化法、粉末内氧化法制备的Cu-1.2A12O3材料,具有高强高导电合金的特征。这说明,通过添加Al、La、Y等第二相活性元素,结合内氧化生成氧化物颗粒,在改善铜氧化物材料中界面润湿性及界面结合性能的同时,还具有多相协同强化的作用,与传统单一强化相比,材料的综合性能明显提高。电接触材料在实际运行状态下存在电弧侵蚀、金属转移等问题,本论文根据触头材料的电弧侵蚀理论,研究了CuAl2O3、CuAl2O3La2O3Y2O3材料在直流阻性负载条件下(20V、20A、接触压力60N、开闭接触工作10000次),材料转移等瞬间电弧特性,分析了铆钉触头材料受电弧侵蚀后的表面形貌特征、金属转移和电弧侵蚀机理,建立了电弧侵蚀过程能量分布的物理模型及能量传导转化公式。获得CuAl2O3、CuAl2O3La2O3Y2O3材料在电弧作用下的金属转移为由阳极向阴极转移,电弧侵蚀形貌由浆糊状、骨架状、空洞状等组成,以及多相氧化物颗粒增强铜基复合材料的耐电弧侵蚀能力优于单一氧化物颗粒增强材料等规律。更多还原

【Abstract】 Particle reinforced dispersion strengthened copper material is a kind of composites material using metal as the matrix and strengthened by metal oxide, intermetallic compounds or nonmetallic fibers. The main strengthening phases include Al2O3, Y2O3, S;O2, TiC, SiC, TiN, Si3N4etc. Dispersion strengthened copper is the key materials used to make electrodes, contacts, leads, microwave tubes and rectified rotor etc, and has been widely applied in electricity, electrical, electronic and electromechanical industry. The main preparation methods at home and abroad for Cu-Al2O3material include mechanical alloying method and power internal oxidation method. The former method is hard to process and has bad mechanical and electrical properties due to the large Al2O3particles and their poor wet ability with copper matrix. The latter method has unstable physical, mechanical and electrical properties due to their complex preparation process, uncontrollable shape and size of the Al2O3particles and low density. Therefore, using above methods cannot solve the problems that Al2O3has poor wet ability with copper matrix, large particles and with nonuniform distribution. Consequently, it influences the yield and comprehensive properties of dispersion strengthening copper and limits its application range.To improve the wet ability of Al2O3with copper matrix, the particle size and distribution of Al2O3in copper matrix and improve the physical, mechanical and electrical properties of materials, in this paper, we present:(1) Using innovation technology roadmap include spray deposition, internal oxidation, rolling, drawing and so on, as well as adding trace rare earth elements in Cu-Al alloy to prepare CuAl2O3、 CuAl2O3La2O3Y2O3composites materials.(2) Through studying the relevance law of process conditions, physical-chemical deposition environment, and microstructure, physical, mechanical and electrical properties of alloy ingots obtained the optimum process parameter to prepare small axis crystalline grain, no segregation, high density, and small dispersion distribution oxide particles cylindrical shape alloy ingots (melting temperature is1300℃, atomization gas pressure is1.5MPa, beginning deposition distance is350mm and deposition device speed is180deg/s). It results that ingot relative density is94%, deposition efficiency is87%and well near net shape. Through the theoretical research of spray deposition, nucleation of atomized droplets and microstructure formation process of ingot, we established microstructure grains distribution model for the spray deposition alloys ingot.(3) Internal oxidation mechanism and its control is one of the core and key technologies to prepare high performance CuAl2O3CuAl2O3La2O3Y2O3composites materials. In this paper, we studied the thermodynamics and kinetics conditions of internal oxidation. Using the DSC analysis ensure the demanding temperature and time within oxidation process, studying the impact of different reaction temperature and time on microstructure and performance of material; using XRD, SEM and HRTEM to analysis lattice constants, composites microstructure changes and the second phase precipitation particles before and after of internal oxidation, the results show that Al2O3、La2O3、Y2O3particles are small, uniform and no segregation internal oxidation, dispersive distribution in the grain and grain boundary of copper substrate. The wet ability is well and the interface is clean. Crystal structure of Al2O3internal oxidation belongs to the hexagonal system, and the misfit ratio for Cu (f=74%)>25%, non-coherent lattice relationship. La2O3belongs to the cubic crystal structure, and the misfit ratio for Cu (f=22%)5%<f=22%<25%, semi-coherent lattice relationship; Y2O3belongs to the cubic crystal structure, and the misfit ratio for Cu (f=3%)<5%, coherent lattice relationship.(4) Through theory research of experiment analysis and precipitation amount of aluminum, diffusion coefficient of aluminum in copper and the oxides generated nucleation and grain growth, we obtained formation of the second phase oxides particles by diffusion control of parabola growth mechanism, in early of internal oxidation (or low temperature conditions), the formation of Al2O3particles was controlled by diffusion rate of Al atom in grain boundary of copper substrate, in late of the internal oxidation (or high temperature conditions), the formation of Al2O3particles was controlled by diffusion rate of Al atom in grain of copper substrate. Through calculation, we obtained the change law of equilibrium solubility of Al in Cu in Cu-Al alloy, precipitates quantity of Al in supersaturated solid solution under different temperature conditions, as well as particles size of Al2O3is between0.45-24.51μm at different reaction stage, which was basically identical with the experiment results of0.5-20μm the oxides particles that CuA10.55alloys at980℃and after2.5h of internal oxidation.In this paper, the influence of different deformation10%,30%,50%,70%,90%on electrical conductivity, hardness, tensile strength and microstructure of CuAl2O3CuAl2O3La2O3Y2O3material have been studied. Meanwhile, we studied the influence of electrical conductivity, hardness and microstructure of material different annealing temperature at700℃,900℃and980℃. Theoretical analysis of strengthening mechanism, the resistance composition, fracture morphology and fracture mechanism were all discussed. The results show that the density of prepared CuAl2O3materials is higher than8.7g/cm3, the tensile strength is more than450MPa, electrical conductivity is greater than47S/m (conductivity>80%IACS). The density of prepared CuAl2O3La2O3Y2O3materials is higher than8.7g/cm3, the tensile strength is more than500MPa, electrical conductivity is greater than48S/m (conductivity>80%IACS). The mechanical properties and electrical conductivity are better than Cu-1.2Al2O3material prepared by mechanical alloying method and powder internal oxidation method. It has the characteristics of high-strength and high-conductivity alloys. The results shows that, through adding a second-phase reactive elements such as Al, La, Y, combined with internal oxidation generates oxide particles, it not only improve wetting and binding properties of the interface, but also has a effect of synergistic enhancement. The materials performance has been improved significantly compared with conventional single enhancement phase.Electric contact material has the arc erosion and metal transfer in actual conditions. In this paper, we researched material transfer of CuAl2O3and CuAl2O3La2O3Y2O3material in DC resistance load conditions (20V,20A, contact pressure is60N, opening and closing contact work is10,000times) according to the arc erosion theory of contact material. The surface morphology features of rivet contact material by arc erosion, metal transfer and arc erosion mechanism have also been studied. We obtained the physical model of arc erosion processes and the energy transfer formulas. Meanwhile, we obtained the law of CUAI2O3、 CuAl2O3La2O3Y2O3material transferred from the anode to the cathode under arc erosion effect, arc erosion morphology composed by starchiness, skeleton and void appearance, arc erosion resistance properties of multiphase oxide particle-reinforced copper matrix composites, which is better than single oxide particle reinforced materials.更多还原