Investigation On Microstructure And Property Of High Strength And High Conductivity Cu-Cr-Zr Alloys

The Cu-Cr-Zr alloy due to its high strength and conductivity,is widely used in the field of integrated circuit lead frame,electrical contact materials,contact wire material etc.This thesis through the composition design of Cu-Cr-Zr alloys,rsearch the effects on microstructure and property of Cr and Zr content on Cu-Cr-Zr alloy.Meanwhile,the reseache also use different heat treatment and cold deformation method to study the relationship between microstructure and property under different conditions,and obtain the best performance of the alloy composition.The experimental results were shown as follows.(1)The as-cast microstructure of Cu-Cr-Zr alloys transfers from columnar dendrite to equiaxed grain with increase of Cr content.Furthermore,the microstructure changes from cellular crystal to columnar dendrite and then to equiaxed grain with increase of Zr content.After solid solution treatment,a large number of solutes dissolves into the matrix,and the particle size of Cr-rich phase and Zr-rich phase both decrease.In addition,after the aging treatment,a large number of precipitated phases disperse in alloy matrix,fine acicular Zr rich phase forms,and some of precipitated phases become coarse.(2)After aging treatment for the Cu-xCr-0.2Zr(x=0.8,1.0,1.2,1.5,2.0)alloy,the best properties occur at the Cr content of 1.0wt%,in which the electrical conductivity reaches 83.2%IACS,the hardness is 138 HB and tensile strength is up to 406.9Mpa.Furthermore,the main fracture morphology in the alloy is dimple.Hence,the mainly fracture mode is ductile fracture.The dimples become looser,and the depth of tear ridges decreases with the increase of Cr content.(3)After aging treatment for the Cu-1.0Cr-xZr(x=0.1,0.15,0.2,0.25)alloy,the best properties occur at the Zr content of 0.2wt%,Furthermore,the main fracture morphology in the alloy is dimple.The size of dimples decreases,the depth of tear ridges decreases,and the number of plastic holes increase with increase of Zr content.Hence,the mainly fracture mode is ductile fracture.(4)With increase of deformation for Cu-1.0Cr-0.2Zr alloy,the electrical conductivity has decrease,followed by increasing.The electrical conductivity is up to 87.9 %IACS at the deformation level of 40% and 60%.Furthermore,when the deformation level is 40%,the hardness is 152 HB.Moreover,tensile strength of alloys increases with increase deformation level,which reaches 491.2MPa at the deformation level of 60%.(5)After the deformations of 20%,40%,60% for Cu-1.0Cr-0.2Zr alloy,a large number of small grains exist in the matrix,and the dislocations occurs the interaction.Moreover,the quantity of small grain increases with increase of deformation level,and the morphology of crushing precipitated phase becomes irregular.Meanwhile,the size of dimple and the depth of tear ridges decreases at the fracture morphology in the alloy.The aging state Cu-1.0Cr-0.2Zr alloy has three kinds of precipitated phases,which are Cu5 Zr,Cr2Zr and CuZr2,respectively.Cu5 Zr presents rod-like and ball-like morphologies.