Study On The Effects Of Cr,Zr On The Microstructure And Mechanical Properties Of Cu

Copper and copper-based alloys are widely used because they have the advantages of high electrical and thermal conductivities,good mechanical properties, outstanding corrosion and fatigue resistance.However,comprehensive properties are more and more required for copper alloys with the rapid development of modern industry.The addition of Cr,Zr into Cu can improve the mechanical properties of pure Cu with a low loss in electrical and thermal conductivities.Thus,this kind of alloy has been studied for a long period and already widely used.Cu-Cr,Cu-Zr,Cu-Cr-Zr alloy are smelted in air with industry pure Cu,pure Cu, Cu-Cr4,Cu-Cr5 and Cu-Zr25.Firstly,The effects of various chromium content,such as 0%,0.3%,0.75%and 1.2%addition,on microstructure and mechanical properties of industry pure Cu containing 0.64%Fe are studied with high temperature box Si-Mo stick resistance furnace.Then,The effects of various Cr addition(W_cr=0.3%,0.53%, 0.76%and 0.99%),Zr(W_zr=0.15%,0.25%,0.35%)and Cr with Zr(W_Cr=0.3%, 0.53%,0.76%,W_zr=0.15%,0.25%,0.35%)on microstructure and mechanical properties of pure Cu are studied with medium frequency induction furnace.Solution strengthening and aging treatment are taken to the alloys prepared.The effects of addition of Cr,Zr into Cu on mechanical properties and microstructure of Cu are studied by the means of optical microscopy,hardness measurement,tensile test,XRD, SEM and EPMA.Analysis and explanation in theory are also given.This paper aims to supply some references to the choice of material and production technique for Cooling Stave of Blast Furnace,Tuyere Small Sleeve of Blast Furnace and Generator Collecting Ring etc.The results show that:(1)Cr and Zr are added into Cu successfully with Cu-Cr and Cu-Zr master alloy in air with high temperature box Si-Mo stick resistance furnace or medium frequency induction furnace and proper smelting technique.(2)The effects of Cr on mechanical properties and microstructure of industry pure Cu is obvious.Both tensile strength and hardness of cast alloys and alloys after heat treatment are improved with the increase of Cr.A small quantity of Fe is beneficial for the mechanical properties of the alloys.(3)The maximum intensity and hardness of cast alloys and alloys after heat treatment prepared with pure Cu are as follows.Cast alloy:Cu-Cr,σ_b=211.5MPa,HB=85.8; Cu-Zr,HB=70.3;Cu-Cr-Zr,σ_b=279.5MPa,HB=89.6.Alloy after heat treatment: Cu-Cr,σ_b=274.6MPa,HB=116.9;Cu-Zr,HB=97.2;Cu-Cr-Zr,σ_b=411.1MPa, HB=147.1.The mechanical properties of the alloys are highly improved after solution and aging treatment.(4)SEM analysis results show that fracture of cast alloys and alloys after solution and aging treatment are toughness rupture.EDAX analysis results show that the microstructure of the alloys is Cu_xZr.(5)XRD and EPMA analysis on alloys prepared with pure Cu show that:α-Cu is the main content in cast alloys and alloys after solution and aging treatment.Cr exists in the forms of Cr or Cr₂Zr,Zr exists in the forms of Cu₅₁Zr₁₄,Cu₅Zr and Cu₃Zr etc. Aging precipitation and related problems are to be studied.(6)The strengthening effects of Cr and Zr to Cu lies in three ways:the strengthening of Cr and Zr to cast alloy,the precipitation strengthening of Cr and Zr and the compound strengthening of Cr and Zr.The mutual effect of Cr and Zr are still to be studied.