Study On Structure-activity Relationship Of "composition-process-structure-properties" Of Cu-(0.5~0.6)Cr-xZr Alloy

Cu-Cr-Zr alloy is a typical precipitation-strengthened alloy with high electrical conductivity,high strength,good heat resistance and excellent ductility,which is widely used in industrial fields such as contact wires,lead frame materials,heat exchangers and nuclear reactor components.In order to meet the increasingly high requirements of the industry for Cu-Cr-Zr alloy,it is necessary to continuously optimize the alloy to obtain good comprehensive properties.Therefore,the optimization of composition of Cu-Cr-Zr alloy,the type of precipitated phase and its transformation and strengthening mechanism have become hot topics.In this paper,Cu-Cr-Zr alloys with different Zr content were used as the research object.The metallographic microscope（OM）,scanning electron microscope（SEM）,energy dispersive spectroscopy（EDS）,electron backscatter diffraction（EBSD）and transmission electron microscopy（TEM）were used to determine the microstructure and properties of each stage.The heat treatment process optimization and aging precipitation behavior of Cu-Cr-xZr alloy ingots were studied.And the structure-activity relationship（SAR）between the“composition—process--struture--properties”of the thermo-mechanical treatment Cu-Cr-xZr alloy were also studied.The following conclusions were obtained:（1）Two morphologies of Cr phase were observed after aging of Cu-Cr-Zr alloy:coffee bean diffraction contrast and elliptical nano-scale Cr phase.With the increase of Zr content,the peak aging time of the alloy was prolonged.When the Zr element content was 0.06 wt.%and 0.10 wt.%,the peak aging time of the alloy was 1 h,and when the Zr element content was 0.16 wt.%,the alloy takes 4 h to reach the peak aging,when the Zr element content increased to 0.21 wt.%,it takes 6 h to reach the peak aging,because the increase of the Zr element content hinders the axial growth of the Cr phase.The Cr phase tends to be spherical or elliptical,delaying the growth and thickening of the Cr phase,thereby prolonging the time to peak aging.（2）With the increase of Zr content,the type of Zr precipitated phase in the peak aging Cu-Cr-Zr alloy is different:when the Zr element content is 0.06 wt.%,the Zr-containing phase is Heusler CrCu₂Zr phase,and when the Zr element content is 0.10.wt.%and 0.16 wt.%,the Zr-containing phase is Cu₅Zr phase,and when the Zr element content is increased to 0.21 wt.%,the Zr-containing phase is Cu₄Zr phase.（3）At the initial stage of aging,the hardness or strength and electrical conductivity increase rapidly,then the hardness or strength decreases slowly after reaching the peak,however the conductivity continues to rise.The Cu-Cr-Zr alloy has a hardness of up to150 HV and a conductivity of 85%IACS.The peak tensile strength of Cu-Cr-Zr alloy can reach 587.8 MPa,the yield strength can reach 499.6 MPa,and the electrical conductivity can reach 80%IACS of thermo-mechanical treatment Cu-Cr-Zr alloy.As the content of Zr increases,the intensity of peak aging also increases.（4）The difference of yield strength of the thermo-mechanical treatment Cu-Cr-Zr alloy with different Zr content increases with the increase of deformation,and the difference increases from 30.4 MPa to 62.6 MPa,which is mainly since the Cu-Cr-Zr alloy with high Zr content has a finer grain after deformation heat treatment,it has the effect of fine grain strengthening.The contribution of fine grain strengthening to the increase of strength difference accounts for about 70%,and the contribution rate of the increase of precipitation relative strength difference is only about 10%.（5）The Zr element in Cu-Cr-Zr alloy can inhibit the growth of recrystallized grains during solid solution,refine grains,and play the role of fine grain strengthening,and the strength of the alloy is improved.In the subsequent processing,Zr Alloys with high element content have larger deformation resistance,more fracture resistance,more severe grain breakage,and fine grain formation.The fine grain strengthening effect is more obvious,which further improves the strength of the alloy.The main reason for the increase in the amount of deformation and the increase in the intensity difference.