Preparation And Properties Of Nano-La₂O₃ Reinforced Copper Matrix Composites

Dispersion strengthened copper matrix composites are often used in electronic and electrical equipment because of the good high temperature and room temperature properties.However,due to the late start of research on this kind of materials in China,the preparation process is not mature enough and various performance indexes of materials need to be further improved.In this paper,the influence of preparation process on the microstructure and properties of Cu-La2O3 composites was explored,with a view to providing theoretical basis and technical support for the design and performance improvement of copper-based composites.In this paper,a combination method of internal oxidation and spark plasma sintering was used to prepare a Cu-La2O3 composite with high strength and high conductivity.Scanning electron microscopy(SEM),transmission electron microscopy(TEM),digital eddy current conductivity meter and electronic universal testing machine were used to analyze the influence of preparation parameters on the microstructure,conductivity,density and mechanical properties of composites.The material’s reinforcement mechanism,conductive property and friction and wear properties of materials were investigated.The result shows:The increase of internal oxidation temperature will promote the nucleation and growth of La2O3 particles.With the increase of internal oxidation temperature,the electrical conductivity of Cu-La2O3 composites increased first and then decreased,while the hardness decreased continuously.The conductivity of the composite with an internal oxidation temperature of 670℃ is as high as 89.34%IACS and the hardness is 99.54 HV.However,when the internal oxidation temperature is higher than 670℃,the performance of the composite material drops sharply.When the internal oxidation temperature is 730℃,the electrical conductivity of the composite has dropped to 69.8%IACS and the hardness is less than 70 HV.For the Cu-La2O3 composite with the best performance(internal oxidation temperature 670℃;internal oxidation time 1 h;K=1.25;sintering temperature 850℃;sintering pressure 50 MPa),tensile strength,yield strength and hardness are 1.23 times,2.2 times and 1.5 times,respectively,of Cu-La alloy,and the electrical conductivity is as high as 92.79%IACS.The strengthening mechanism of Cu-La2O3 composites mainly includes fine grain strengthening and dispersion strengthening.The main factors for increasing the resistivity in this composite material are phonons,grain boundaries and La2O3 particles,and the total resistivity contribution is 1.79μΩ·cm.The wear resistance of Cu-La2O3 composite is significantly higher than that of pure copper.With the increase of friction speed and load,the wear form of Cu-La2O3 composites is gradually transformed into oxidation wear and delamination wear by abrasive wear.