The Microstructure And Electrical Conductivity Of Cu-1.2Cr-0.6Zr Alloy Strengthened By Surface Plastic Deformation

Cu-Cr-Zr,a high strength and high conductivity alloy,is a typical precipitationstrengthened copper alloy,which is widely used for high-iron contact wires,electric welding electrodes,et al.In order to improve the strength of the Cu-C-Zr and keep its high conductivity as far as possible,several methods such as components design,severe plastic deformation and aging are usually used.However,these methods cause a series of problems which affect conductivity,such as serious lattice distortion,a large number of dislocations proliferation and agglomeration,and the growth of the second phase,etc.In this paper,the surface shear strain was applied to the pre-drawn Cu-Cr-Zr alloy bars by torsional deformation.The shear deformation occurs at the surface of the sample and extends to the core,which forms a “core-shell” multi-stage structure composed of a surface“deformation layer” and an inner “origin core region”.The “core-shell” structure increases the surface hardness of the Cu-Cr-Zr bar while maintaining the high conductivity of it.The specific works on this direction are as follows:(1)This study used a low alloy composition of Cu-1.2Cr-0.6Zr.The Cu-Cr-Zr material library was established in the finite element software.And then simulation analysis of torsion on the Cu-Cr-Zr alloy bars were carried out with the different deformation rates and deformations quantities.The results concluded: the Cu-1.2Cr-0.6Zr was broken when it was twisted for 9 turns;The maximum stress on the surface of the bar during the torsion process is much greater than the stress on the core.According to the simulation results,the shear stress was gradually increased from the surface to the core of the bar.Therefore,the surface plastic deformation quantity strengthening of Cu-1.2Cr-0.6Zr alloy bar can be realized by controlling the deformation;(2)The microstructures of the core and surface of Cu-1.2Cr-0.6Zr alloy before and after plastic deformation were characterized by XRD,OM,SEM,EBSD and TEM.And the microstructure,grain,dislocation,the second phase,lattice distortion,etc.were analyzed;(3)The microhardness of the surface and the core of Cu-Cr-Zr alloy bar before and after plastic deformation were tested on the microhardness meter;The resistance values of the Cu-Cr-Zr alloy were tested by QJ44 double-arm bridge and KEITHLEY meter;The effect of different deformation on hardness and conductivity of Cu-Cr-Zr alloy bars were analyzed.The results show that after the surface plastic deformation of Cu-1.2Cr-0.6Zr,the core hardness value increased from 150 HV to 186 HV,and the surface microhardness value increased from 190 HV to 201 HV.The conductivity of the alloy was reduced from the original 79 % IACS to 72~73 % IACS.