Preparation And Mechanical Properties Of Molybdenum-Molybdenum Carbide(In-Situ) Reinforced Copper Matrix Composite

Copper-based composite materials have excellent electrical conductivity,high strength,thermal conductivity and high temperature resistance,so they are widely used in electric power,electronic information,machinery manufacturing and rail transit.Generally speaking,the way to improve the performance of copper-based composites is to add a reinforcing phase.The addition of the reinforcing phase will increase the strength and wear resistance of the composite,but will reduce its electrical conductivity.At the same time,the conductivity,size and distribution of the reinforcing phase directly affect the performance of the composite material.Mo is a metal with high melting point,small thermal expansion coefficient and good electrical conductivity,and Mo carbide Mo₂C also has the characteristics of high melting point,high hardness,high thermal stability,and new functions of mechanical stability and excellent corrosion resistance.It is a good choice to use Mo and Mo₂C as reinforcing phases to improve the strength and wear resistance of copper composites and maintain good electrical conductivity.In this thesis,graphene(Gr)is prepared by an improved electrolytic stripping process.Use Scanning Electron Microscope(SEM),Transmission Electron Microscope(TEM),Raman Spectrometer(Raman)to characterize its microscopic morphology and structure;Then use Cu powder,nano Mo powder and Gr as a carbon source as raw materials.The three are designed with different proportions,and the planetary high-energy ball mill is used to prepare a uniform composite powder of Cu-based solid solution with Mo supersaturation,nano-Mo powder and Gr through mechanical alloying.Use metallographic optical microscope(OM),scanning electron microscope(SEM),X-ray diffraction(XRD)and microhardness test(HV)to analyze the powder's microscopic morphology and phase structure of the composite and performance testing after mechanical alloying;Subsequently,the composite powder is prepared by vacuum hot pressing sintering to obtain Mo-Mo₂C(in-situ)/Cu composite material.Use metallographic optical microscope(OM),scanning electron microscope(SEM),energy spectrum(EDS),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)to analyze the phase composition and microscopic morphology of the composite material,tested the density,microhardness,electrical conductivity,tensile strength and wear resistance of the composite material.The influence of reinforcement phase content and ball milling time on the properties of Mo-Mo₂C(in-situ)/Cu composites was studied.Research indicates:1.Gr was successfully prepared using an improved electrolytic stripping process,and the preparation efficiency was significantly improved.2.The Cu phase particle size in the Cu-Mo-Gr mixed powder decreases with the extension of the ball milling time.In XRD,the diffraction peak of Cu phase is broadened,the intensity is reduced and shifted to the left.The intensity of the diffraction peak of Mo gradually decreases,indicating that Mo continues to dissolve into Cu,and the grain size of Cu decreases and Mo is solid in copper.The increase of soluble amount is more obvious in the early stage of ball milling,and the speed slows down as time increases.For the amount of solid solution,mixed powders with different proportions increase with the increase of the amount of Mo under the same milling time;for the same proportion of powder,with the extension of the milling time,the amount of solid solution increases.3.The composite powders of all proportions are sintered in the same process,namely,first cold-pressed at 240 MPa to form a blank,and then vacuum hot-pressed sintered at 30MPa at 900°C for 1 hour.During the sintering process,the Mo solid solution in Cu precipitates and is evenly distributed in the matrix.Excessive Mo reacts with graphene to generate Mo2C to prepare Mo-Mo2C(in-situ)/Cu sample;By comparing the properties of the samples with different composition ratios,the Cu_93.5Mo₆Gr_0.5(mass fraction ratio)was obtained.The samples prepared by 20h high-energy ball milling and subsequent hot pressing sintering have a tensile strength of 661MPa,a conductivity of 65.97%IACS,the microhardness reaches 231.1HV,and it has good wear resistance,that is,it has good comprehensive performance.