Preparation And Relative Basic Research On The Copper Alloy With High Strength And High Conductivity

A series of high-performance copper alloys including Cu-2.5Fe-0.03P,Cu-0.1Fe-0.03P,Cu-Ag-Cr and Cu-Ag-Zr were investigated incorporating work supported by National Defense Basic Research Project entitled "Basic research of special copper alloy materials for E-military project and preparation technology" and National Natural Science Foundation Project called "Existing forms and mechanisms of trace Ag,Zr and rare earth in high-strength, high-conductivity Cu alloy".For Cu-0.1Fe-0.03P copper strips,we have studied their mechanical properties and electrical properties and their microstructures were examined by OM,X-ray diffraction and electronic microanalysis.For Cu-2.5Fe-0.03P alloys,we have studied their structure changes under different aging and heat treatment processes.Furthermore, the influence the addition of trace amount of Ag,Cr,Zr and thermo-mechanical treatment on strength and electrical conductivity of Cu-Ag-Cr and Cu-Ag-Zr alloys were conducted.The main results out of this work are summarized as the follows:1.The existence of phosphor promoted hydrogen absorption during melting of Cu-0.1Fe-0.03P alloys through deoxidization. Hydrogen-riched pores gathered and grew up under external stress during hot rolling to form bubbles leading to surface defects for oxidizing gas transport and penetration underneath and facilitate the formation of Cu₂O inside the alloy.The brittle Cu₂O was either broke up or underwent deformation under pressure and migrated to the surface during cold-rolling and final rolling processes.Since the bond between Cu₂O and copper matrix was relative weak,micro-cracks often occurred at their interfaces during cold rolling.The expansion of micro-cracks and the break up of bubbles with continuous deformation eventually resulted in surface peeling of Cu-0.1Fe-0.03P alloy.2.The optimal thermo-mechanical treatment condition for Cu-0.1Fe-0.03P alloy strips was found out to be such that in situ solution treatment before 95%cold rolling and followed by aging at 500℃for 2h. The corresponded tensile strength,yield strength,elongation and electrical conductivity are 258MPa,192MPa,22.5%and 86%IACS respectively.Their microstructure is consisted of solid solution matrix and dispersed secondary phase particles such asγ-Fe,Fe₃P and Fe₂P.The main strengthening effect came from substructure and precipitation strengthening.3.The results of pole figure and ODF analysis show that The major texture of Cu-0.1Fe-0.03P alloy product sheet is {110}＜112＞brass texture,the minor textures are {110}＜100＞gauss texture,{123}＜634＞S texture and {001}＜100＞cubic texture.The crystal texture should be responsible for in-plane mechanical anisotropy of the product sheet.4.Compared with traditional processing methods,the combination of horizontal continuous casting and cold rolling and annealing offers shorter process time,lesser investment,lower cost,higher yield,and faster construction etc..Alloy strips prepared by this method have lower tensile strength,lower electrical conductivity,lower softening temperatures and higher elongations.However,the strips made by this new method(without hot rolling as did in the traditional methods) showed larger shrinkage defects during solidification which led to ablation and scale peel of during cold rolling.5.Utilizing traditional processing(hot rolling before solution treatment prior to cold rolling and aging),iron and phosphor exist in the form of singly atomic Fe and Fe₃P compound.Besides Sub-structure strengthening came from the thermo-mechanical treatment,precipitation hardening of Fe₃P and the formation of Fe particles led to high strength6.Equation of kinetic of Phase-change/transition/transformation for aging process of Cu-2.5%Fe-0.03%P alloy can be deduced by the variation of conductivity as a function of time.For example, f=1-exp(-0.14749t^0.52564) at 550℃.7.The tensile strength,yield strength,elongation and electrical conductivity of Cu-0.1Ag-0.5Cr Strips treated at 950℃/1h and 30% pre-cooling deformation and 450℃/4h aging are 397MPa,335MPa, 14.8%and 77.5%IACS respectively.Addition of trace amount Ag exists mainly in solid solution while that of Cr as singly Cr particles.The main hardening mechanism is due to Ag solution,sub-structure strengthening and Cr particles precipitation.8.The optimal processing for Cu-0.1Ag-0.2Zr alloy is 950℃/1h solution and 30%pre-cooling deformation and 450℃/4h aging.The tensile strength,yield strength,elongation and electrical conductivity for the strip made this way are 373MPa,327MPa,10%and 95.7%IACS respectively.Addition of trace amount of Zr exists mainly as Cu-Zr compound particles.The appearance of these particles retards recovery and recrystallization significantly.The strengthening mechanism is solid solution strengthening of Ag,sub-structure strengthening produced by the pre-cooling deformation and precipitation strengthening of Cu-Zr particles...