Effect Of Microalloying And ECAP Deformation On Microstructure And Properties Of Pure Copper

With the development of modern industry,the properties requirements of materials have been continuously improved,and traditional high-conductivity pure copper has been unable to meet the demand for high-performance materials in emerging technology fields due to its low strength.To solve the problem of low strength of high-conductivity pure copper,this paper uses the ECAP to strengthening it.The ECAP has obvious effects of deformation and industrialization.At the same time,it has less influence on the conductor copper conductivity.The multy-passes extrusion of the route A,Bc,and C were performed on the single crystal copper using the internal corner ? = 90°,105°,and 120° molds,and the material was extruded through OM,XRD,SEM,EDS,EBSD,etc.The microstructure,texture evolution are studied,the mechanical properties and conductivity are also concerned.Subsequently,micro-alloying of pure copper was carried out by adding trace amounts of Zr and Si elements to increase its strength,and secondary strengthening was carried out by a solid solution+liquid nitrogen cooled ECAP+aging treatment process.At the same time,explores the effect of precipitation on its strength and electrical conductivity.The results show that the single crystal copper is pressed after 4 passes ECAP by route A,two different shear bands are formed in the structure.The shear bands in each direction are evenly distributed and parallel to each other;by route Bc,the direction of the shear bands is varied and intersecting to form a large number of cell structures.In the single crystal structure using the route C,many parallel and uniform shear bands are formed.When single crystal copper has been deformed 4 passes by 120° of the die,the original <111> orientation changes to the {001}<110> texture by route A,the {111}<110> texture by route Bc,and the {111} <110> and {112}<110> double textures by route C;after 4 passes ECAP by 105° of the die,the route A is {110} <112> and {124} <211> texture,and the route Bc is {112} <110> texture,route C is {110} <110> texture.During the ECAP process,the strength of single-crystal copper increases with the increase of ECAP passes.At the same time,the effect of single-crystal copper strengthening in route A extrusion is higher than that of the other two routes;When use the route Bc,the electronic conductivity rate of loss is minimal.In the final,with the 105° mold,after 5 passes by the route A,the tensile strength increased from the original 168 MPa to a maximum of 435 MPa,while the conductivity remained at 97% IACS.Through comparative study,it is found that <110> silk fabric is conducive to maintaining the conductivity of materials.When the as-cast Cu-Zr-Si alloy is aged in liquid nitrogen for 1pass ECAP+350°C,450°C,and 500°C for 0.5-4 hours,the precipitates precipitate mainly along the grain boundaries,its looks like short rods and lumps.With the increase of aging temperature and time,the precipitation phase gradually increased.The maximum tensile strength of as-cast Cu-Zr-Si alloy obtained by liquid nitrogen cooling at ECAP+450°C for 2 h was 375 MPa.The elongation was 20.6%,the electrical conductivity was 82%,and the hardness was 137 Hv.ECAP can greatly improve the strength of single crystal copper and maintain its high conductivity,the strength after deformation is 259% for the original single crystal copper,and the conductivity is only reduced by 3%.At the same time,reducing the internal angle of the mold and using a suitable extrusion route can further increase the material strength.Compared with room temperature extrusion,the strength of Cu-Zr-Si alloy at low temperature is 13.6% higher than that at normal temperature,indicating that low temperature cold extrusion process is an effective means of strengthening the material and can further increase the material strength.