Preparation And Heat Treatment Process Of Cu-Cr-Zr Alloys

Cu-Cr-Zr alloy is a structural function material with comprehensive physical and mechanical property,which has high strength,good electrical and thermal conductivity as well as corrosion resistance.Cu-Cr-Zr alloy is widely used in fields of nuclear facilities,large-scale IC(integrated circuit)lead frame,high-speed railway lines,resistance welding electrode and continuous casting mold etc.It is very difficult to cast in atmospheric conditions,because chrome and zirconium are elements that can be oxidized easily and have high melting points.The study of melting technology of Cu-Cr-Zr in atmospheric conditions provided a new method for the study and development of high performance Cu-Cr-Zr alloy.Meanwhile,Cu-Cr-Zr is a typical ageing precipitated copper alloy.Therefore,it has important practical significance and theoretical value to improve its strength,hardness and electrical conductivity with the method that combined alloying,heat treatment and cold deformation.This paper studied the preparation technology of high-strength and high-conductivity Cu-Cr-Zr alloy under the anti-vacuum(atmospheric)conditions and the covering agent of this'alloy,and analyzed the effect of covering agent and deoxidizer on oxidation burning loss and yield of alloy elements.Meanwhile,the micro structure of alloy was analyzed by means of SEM,TEM,EDS.The evolution law of processed alloy structure and property was studied by detecting the hardness and electrical conductivity under different technologies for heating processing with Brinell hardness tester and Eddy current conductivity meter,the conclusions can be drawn as follows:1.It is difficult to smelt Cu-Cr-Zr alloy at atmospheric condition and charcoal,phosphorus flake graphite and special cover agent must be used in high-temperature smelting,mean while a large amount of carbon will existed in the ingot structure if smelting in graphite crucible,while the ingot structure is very clean if smelting in Magnesia crucible.The research result could basically solve problems,such as burning loss and the variance of the compositions and then obtained the ingot casting with smooth surface and good density.2.Cu-0.71Cr-0.18Zr alloy has a strong strengthening effect on aging treatment.The hardness,conductivity and tensile strength in casting respectively are 50.4HB,68.7%IACS and 124MPa.As the rising of aging temperature and the extension of time,the conductivity remains in a relatively high level because of the continuous dilution of solid solution and the decrease of electron scattering effect.However,the coarsening of the secondary phase caused the continuous decrease of hardness after reaching the peak of hardness,therefore,the optimal heat treatment is solute the solid for 30 min under the temperature of 960 ? and then aging it for 120min under the temperature of 500 ?,at the time,the alloy has better comprehensive property,its hardness,conductivity and tensile strength respectively are 134HBW,89.93%IACS and 362MPa.3.The tensile strength of Cu-Cr-Zr alloy increases as the rising of temperature of solid solution,at 500 ? aging treatment after high-temperature solid solution,the tensile strength of alloy shows the maximum value as 362MPa,when the time of aging treatment is over 240min,the increase of tensile strength is inconspicuous.The tensile fracture of Cu-0.71Cr-0.18Zr alloy under different aging treatment temperature is mainly consisted of morphologies such as micropore,dimple and tear ridge etc.It is obvious that thick undissolved Cr phase is existed in dimple.4.The measurement of elastic modulus in alloy is very necessary for the further study of alloy's elastic property.The alloy's elastic modulus is mainly decided by the alloy's component and is little affected by the heat treatment.The addition of Zr can increase the alloy's elastic modulus,so the alloy's elastic property can be improved by changing its compositions.5.After the solid solution treatment at 960 ? for 30min and a aging treatment at 500 ?for 120min,the supersaturated solid solution of Cu-0.71Cr-0.18Zr alloy is decomposed into Cr2Zr phase and CusZr3 phase.The precipitated phase of a large amount of coherency dispersion is an important factor for the strengthening of aging treatment.Fine precipitates have dislocated on the pinning,which makes it difficult for the dislocation to move in the aging process,as a result,the process of deformation-recovery and re-crystallization are delayed,the alloy's hardness is increased.The precipitated phase of Cu-0.71 Cr-0.18Zr alloy at 500 ? for 360min aging treatment are Cr phase and Cu10Zr7 and the strength reaches its peak as 362MPa at this moment.