Study On Microstructure And Properties Of Cu-Y₂O₃ Composites Prepared By Liquid Phase In Situ Reactive Ball Milling

In recent years,copper matrix composites have been widely used in aerospace,automobile,electronics,rail transit and many other fields,but with the development of modern industrial technology,the demand for its high strength,high conductivity and high heat resistance is increasingly intense,which poses new challenges to the existing preparation technology of copper matrix composites.As a rare earth oxide,Y₂O₃is often added to copper matrix composites as an enhanced phase due to its high melting point and good chemical stability.However,Cu-Y₂O₃composites prepared by traditional powder metallurgy and internal oxidation methods have many problems,such as poor interface bonding,insufficient particle oxidation effect,complicated preparation process,high energy consumption,mechanical properties and electrical properties of materials can not meet the requirements of use.Based on this,a new liquid phase in situ reactive ball milling technology was developed to obtain Cu-Y₂O₃composites using Cu powder and Y powder as raw materials and H₂O₂as liquid phase oxygen source.The effects of reinforcing phase content,pellet ratio and milling time on the microstructure and properties of composites were studied by metallographic microscope,scanning electron microscope,transmission electron microscope,Vickers hardness tester,conductivity tester,universal electronic test system and friction and wear testing machine.The results showed that:（1）The thermodynamic calculation results of the Cu-Y-H₂O₂system prove that the in-situ reaction of Cu-Y₂O₃can be spontaneous.The XRD analysis results confirm that there is an obvious Y₂O₃diffraction peak in the composite material,and the intensity of the diffraction peak increases with the increase of the content of Y₂O₃.In situ generation of Y₂O₃particle size small,size is about 50 nm,with the same between Cu with face-centered cubic crystal degree to the relationship in the paper are as follows:（422）Y₂O₃//（1 11）Cu与[011]Y₂O₃//[112]Cu,form stable metallurgical bonding between the two.（2）With the increase of Y₂O₃content,the microhardness and tensile strength of Cu-Y₂O₃composites increase,while the conductivity of Cu-Y₂O₃composites decreases slightly.When the content of Y₂O₃is 7 vol.%,the comprehensive performance is the best.At this time,the conductivity is 79.1%IACS,the tensile strength is 326.3 MPa,the elongation is about 10%,and the hardness is 181.3%higher than that of pure copper.The strengthening mechanism of the composites is Orowan bypass strengthening mechanism and fine grain synergistic strengthening.（3）With the increase of pellet ratio,the particle refinement effect is better,and the density of the material gradually decreases,which indirectly leads to the gradual decline of the electrical conductivity,from 83%IACS of pellet ratio 4:1 to 73.6%IACS of 12:1.However,due to the enhancement of the second phase particles of dispersion and the refinement of the grain size of Cu,the Vickers hardness and tensile strength of the material are gradually increased.When the pellet ratio is 12:1,the hardness reaches 141.1 HV and the tensile strength reaches 368.7MPa,but the elongation decreases to only 5.5%.It was found that the particle distribution of the second phase of the sample was greatly improved and uniform dispersion was achieved.At this point the hardness reaches 198.4 HV.On the contrary,with the increase of milling time,the density decreased rapidly,which was lower than 97%densification,and the conductivity was only 57.8%IACS at 40h of milling.In terms of tensile properties,the tensile strength and yield strength of the material reached535.7 MPa and 519.5 MPa after milling for 40 h,and the yield ratio increased significantly.Although the resistance to plastic deformation was improved,the work hardening ability of the material was almost lost,and the fracture morphology was more inclined to brittle fracture.（4）The test results show that when the softening temperature of Cu-7 vol.%Y₂O₃composites is 800℃,the yield strength of Cu-7 Vol.%Y₂O₃composites remains at 302.0MPa,and the addition of Y₂O₃significantly improves the heat resistance.With the increase of Y₂O₃content,the friction coefficient of composites decreases,the width of wear marks Narrows,the volume wear rate decreases,and the wear performance improves.The wear mechanism is adhesive wear and abrasive wear.