【摘要】 采用真空雾化和内氧化方法制备钇（Y）含量为0,1%和3%（质量分数）的纳米Al₂O₃弥散强化铜粉末，并通过放电等离子烧结（SPS）技术制备铜基复合材料。通过透射电镜（TEM）分析复合材料第二相尺寸为纳米级，元素组成为Al-Y-O化合物。利用扫描电子显微镜（SEM）和激光共聚焦显微镜（LSCM）观察分析复合材料磨损表面形貌，研究了Y含量对复合材料摩擦磨损性能的影响。结果表明，随着Y含量的增加，磨损率先减小后增大。Y添加量为1%时，形成的稀土氧化物尺寸细小仅为50 nm且弥散分布于基体中，有效强化基体提高了耐磨性，此时材料的耐磨性能最佳，磨损率为4.450×10^-4 mm³·m。Y含量增加至3%时，由于过量的稀土形成的复相稀土氧化物尺寸粗大且倾向于沿着晶界析出，在磨损过程中这些粗大的颗粒相成为应力集中源，在剪切应力作用下出现大量的微裂纹和颗粒剥离，导致材料耐磨性下降。稀土元素Y对铜基复合材料的改性作用表现为细化晶粒，改善了材料的微观组织结构，硬质颗粒弥散分布提高材料力学性能，又作为承载相提高材料耐磨性。更多还原

【Abstract】 Copper and copper alloys have good electrical and thermal conductivity,which play an important role in many fields such as electronic technology,aerospace and so on.However,copper has low tensile strength,low hardness and poor wear resistance,which limits its further application.For this reason,researchers have improved the mechanical properties of copper and copper alloy through solution strengthening,deformation strengthening,precipitation strengthening,particle dispersion strengthening and other technical means.Dispersion strengthened copper is a kind of high-performance copper alloy with fine dispersion reinforced phase particles distributed in copper matrix.Due to the existence of reinforcement particles with good chemical stability and thermal stability,this kind of copper alloy has superior electrical conductivity and good mechanical properties.At present,the commonly used strengthening particles are:Al₂O₃,TiB₂,SiC,etc.among them,Al₂O₃ dispersion strengthened copper is a kind of dispersion copper alloy which is widely used.At room temperature and high temperature,the strength and friction and wear properties of the copper alloy are significantly improved.In the field of metal materials research,rare earths are often added to metals as beneficial elements to improve metal structure and performance.Studies have found that rare earths in copper and copper alloys can purify the structure and refine the grains,thereby improving its cold and hot processing performance,electrical conductivity,corrosion resistance and wear resistance.The nano-Al₂O₃ powder with Al content of 0.6%,yttrium （Y） content of 0,1%and 3%of nano-Al₂O₃ was prepared by vacuum atomization and internal oxidation with Cu-20%Y,Al-85%Y intermediate alloy block and pure Cu plate （purity>99.9%） in this paper.The powder making process was as follows:the alloy melt with uniform composition was obtained by vacuum induction melting,and the powder was atomized by N₂,and the atomization pressure was 7.0 MPa.The selected-63μm powder was fully contacted with air at 300℃，oxidized for 4 h at 700℃，then was reduced by H₂ for 4 h at 700℃，and then the prepared powder was sintered intoΦ20 mm×10 mm sample by spark plasma sintering （SPS） technology.The sintering process was as follows:sintering temperature was 900℃，holding time was 5 min,sintering pressure was 40 MPa.Mft-5000 friction and wear tester was used to test the contact friction and wear between rotating ball and disc,the phase composition of the composite powder was analyzed by X-ray diffractometer （XRD）.The microstructure of the sintered sample was observed by metallographic microscope （OM） and scanning electron microscope （SEM）.The element composition and size distribution of the dispersed phase were analyzed by scanning transmission electron microscope （STEM） and high-resolution transmission electron microscope （HRTEM）.Laser confocal microscope was used to analyze the three-dimensional morphology of sintered samples after friction and wear.By analyzing the microstructure and phase of the powder,the results showed:the rare earth element Y could refine the grains and make the grain distribution more concentrated.The average grain size of atomized powder without Y was 2.73μm,and the average grain size of atomized powder was 1.43μm when Y content was 3%.Y existed in the form of Cu₄Y in atomized powder,Al in the form of Al₂Y₄O₉ and Al₂O₃ in the internal redox powder,and Y existed in the form of Al₂Y₄O₉ and Y₂O₃.The density of SPS sintered samples was higher than 98%by drainage method.With the increase of Y content,the hardness of the composites increased,the conductivity decreased,the average diameter of the second phase increased from 8 to 96 nm,and the distribution of the second phase changed from dispersion distribution to grain boundary distribution.By studying the friction and wear properties of sintered samples,the results showed the content of Y had little effect on the friction coefficient,and the wear rate first decreased and then increased with the increase of Y content.The results showed that the wear resistance of nano-Al₂O₃ dispersion strengthened copper with 1%Y content was the best and the wear rate was 4.450×10^-4 mm³·m^-1,due to the moderate size and uniform distribution of dispersed phase.The wear resistance of the composites with Y content of 3%,due to the large size of the second phase particles,was easy to fall off in the friction and wear process,resulting in the decrease of wear resistance.The addition of Y could improve the friction and wear properties of alumina dispersion strengthened copper.When the content of Y was 1%,the size of the rare earth oxide was only 50 nm and dispersed in the matrix,which effectively strengthened the matrix and improved the wear resistance.When the content of Y increased to 3%,due to the large size and tendency to precipitate along the grain boundary,these coarse particles became the source of stress concentration in the wear process,resulting in a large number of micro-cracks and particle peeling under the action of shear stress,resulting in the decrease of wear resistance.The modification effect of rare earth element Y on copper matrix composite showed that the grain size was refined,the microstructure of the material was improved,the hard particle dispersion distribution improved the mechanical properties of the material,and as a bearing phase,the wear resistance of the material was improved.更多还原