The Research Of MoSi₂ Dispersion Strengthened Copper Composite Material

Dispersion and strengthened copper are widely used in fields of automobile and electron industry.Metal silicide MoSi₂ can be used as consolidated phase of electric conduction copper owing to its excellent propcrties such as high strength and hardness, good corrosion resistance in high-temperature,thermal expansion coefficient matching with copper,good electric and heat conductivity in itself and furthermore,it has small effect on electric conductivity.So far no report about MoSi₂ dispersion and strengthening copper-base composite has been seen and this paper focuses on elementary research about preparation and properties of above material.Firstly,MoSi₂ powder was dispersed and refined by high-energy wet milling method and then two different composite powders of MoSi₂/Cu were prepared by chemical package and mechanical milling method,respectively.Then bulk MoSi₂/Cu composite was prepared by hot pressed sintering technique.Secondly,the evolution of particle size,grain size and micro-strain of MoSi₂ powder with the increase of milling time were investigated by means of laser grain analytic instrument(LPSA),X-ray diffraction(XRD)and scanning electronic microscope(SEM).At the same time, microstructure feature and refining mechanism of MoSi₂ powder by wet milling were also discussed.Thirdly,systematic research about processing and properties by chemical package method were performed,form mechanism and influence factors of coated structure were discussed.Fourthly,structure and morphology characteristic and microstructure evolution were researched.Then bulk MoSi₂/Cu composite was prepared by hot-pressure sintering technique.Finally,mechanics and electricity properties,microstructure,density of MoSi₂/Cu sinter specimens were also studied.The results showed that the phase transformation of MoSi₂ didn't occur after wet milling for 100h,whereas grain size which decreased from 13.634μm to 0.140μm. Distribution plot for particle size presented the double-hump character of coexistence of sub-micro zone and nanometer zone.Average crystal grain also decreased from 78.41nm to 14.2nm;the grain size and micro-strain exhibited inversion relationship of e=17.0844D^-0.4468during milling.Refinement of particle mainly depended on grind medium which entered micro crack and played the roles of glutting fission, accelerating crush of powder in the early stage of milling;grind medium coated on the surface of particle,preventing aggregation in after stage.Cu coated MoSi₂ composite powder can be successfully synthesized by chemical package method.Grain surface of MoSi₂ was coated by copper minicrystal and dispersion property of MoSi₂ grain was obviously improved;grain size and morphology of MoSi₂ have big influence on coat ability of composite powder;acid solution can effectively prevent aggregation of composite powder and make better coat effect.The coat structure was dependent on aggradations of copper on the surface of MoSi₂ grain and aggregation control of composite powder.The composite powder presented the following evolvement process during milling: at first forming mechanical coat body and then crashing and refining.The composite powder had optimal property after 60h milling with the crystal size of copper decreased from 54.3nm to 14.4nm and that of MoSi₂ decreased from 69.4nm to24.1nm, respectively but further milling took little change.The diffraction peak intensity and grain size of MoSi₂ powder first decreased and then increased;while micro-strain presented abnormal phenomena which first increased and then quickly decreasedThe properties of hot-pressure sintering samples were superior to their counterpart sintered in conventional normal atmosphere protection.Dispersion and strengthened copper composite by MoSi₂ with good property can successfully synthesized by hot-pressure sintering process.When same content MoSi₂ was added to the samples, the properties of hot-pressure sintering samples prepared by mechanical milling method were superior to those prepared by chemical package method.With the increase content of MoSi₂,the densities and electric conductivity of samples presented a downtrend while package hot-pressure material presented abnormal phenomenon of continuous increase of hardness and gradual decrease of tensile strength.Dispersion and strengthened copper composite with 2%MoSi₂ content may be produced under the optimal process conditions that were proposed:relative density was 97.44%,electric conductivity was 68.42%IACS,hardness was HV142,tensile strength was 356.21MPa.