【作者】 戴姣燕；

【导师】 尹志民；

【作者基本信息】 中南大学 ， 材料物理与化学， 2009， 博士

【摘要】 本文结合国防基础研究项目“军工电子用特种功能铜合金材料及其制备技术的基础研究”和国家自然科学基金项目“微量Ag、Zr、稀土等在高强导电铜合金中的存在形式和作用机制”,采用力学性能与电导率测试、金相、X-射线衍射和电子显微分析方法,首先研究了中强高导Cu-0.1Fe-0.03P铜合金薄带生产过程中的若干问题;然后对高强高导Cu-2.5Fe-0.03P合金在不同加工—热处理状态下组织性能演变规律及其时效析出特性进行了研究;在此基础上还研究了微量Ag、Cr和Zr及形变热处理对高强高导Cu-Ag-Cr和Cu-Ag-Zr合金组织性能的影响。主要结论如下:1.Cu-0.1Fe-0.03P合金熔炼过程中,P的脱氧作用增加了铜熔体的吸氢倾向。热轧条件下,富氢气孔在外应力作用下聚集长大,形成热轧板鼓泡缺陷,鼓泡周围组织疏松,氧化性气体容易渗透进入鼓泡内部形成岩盐状Cu₂O结晶体。在后续的多次冷轧和精轧过程中,岩盐状Cu₂O结晶体受到压力的作用发生破碎或小量变形并且越来越向表层移动。由于Cu₂O结晶体与铜基体之间的结合力很弱,冷轧过程中微裂纹就在结合面处产生。继续变形时,微裂纹不断扩展、鼓泡破裂,最后从铜基体上剥落下来,导致薄板表面出现起皮掉渣现象。2.Cu-0.1Fe-0.03P合金合宜的形变热处理工艺是热轧后在线固溶—95%冷轧变形—500℃/2h时效处理,在此条件下,合金的抗拉强度、屈服强度、延伸率和电导率分别为258 MPa、192 MPa、22.5%和86%IACS。Cu-0.1Fe-0.03P合金成品薄带的显微组织结构为固溶体基体和弥散分布的第二相颗粒,第二相颗粒分别为γ-Fe、Fe₃P和Fe₂P。亚结构强化和析出强化是Cu-0.1Fe-0.03P合金强化的主要原因。3.极图和取向分布函数（ODF）织构分析表明水平连铸卷坯—冷轧—退火新工艺制备的Cu-0.1Fe-0.03P合金薄带以{110}＜112＞黄铜织构为主,此外还有较弱的{110}＜100＞高斯织构、{123}＜634＞S织构以及{001}＜100＞立方织构,晶体学织构是薄带出现力学平面各向异性的主要原因。4.与传统工艺制备的薄带性能相比,水平连铸卷坯—冷轧—退火新工艺具有流程短、投资少、成本低、成品率高、建设周期短等显著优点,是一种很有前途的工艺,但是新工艺制备的合金薄带抗拉强度、电导率和软化温度稍低而延伸率稍高。此外,新工艺没有经过热轧,铸锭过程中的疏松缩孔没有焊合,冷轧后容易出现起皮现象,解决的办法是提高铸坯的质量,消除铸锭中的疏松和缩孔。5.热轧—在线固溶—冷轧—时效态Cu-2.5Fe-0.03P合金中的Fe和P以Fe₃P和Fe相形式存在,合金的高强度来源于形变热处理产生的亚结构强化及Fe₃P和Fe粒子的析出强化。6.Cu-2.5%Fe-0.03%P合金时效过程的相变动力学方程可以由导电率随时间的变化推导出来,导电率和时效过程中第二相析出的体积分数有很好的对应关系,550℃时效时的相变动力学方程为:f=1-exp(-0.14749t^0.52564)。7.Cu-0.1Ag-0.5Cr合金带材合宜的形变热处理工艺为950℃/1h固溶—30%预冷变形—450℃/4h时效,在此条件下,合金的抗拉强度、屈服强度、延伸率和电导率分别为397MPa、335MPa、14.8%和77.5%IACS。微量Ag在时效态Cu-0.1Ag-0.5Cr合金中主要以固溶形式存在,微量Cr则主要以单质Cr粒子形式存在,Cu-0.1Ag-0.5Cr合金的强化机制是Ag的固溶强化、预冷变形引入的亚结构强化和Cr粒子的析出强化。8.Cu-0.1Ag-0.2Zr合金带材合宜的形变热处理工艺为950℃/1h固溶—30%预冷变形—450℃/4h时效,在此条件下,合金的抗拉强度、屈服强度、延伸率和电导率分别为373MPa、327MPa、10%和95.7%IACS。微量Zr在时效态Cu-0.1Ag-0.2Zr合金中主要以铜锆化合物粒子形式存在,它能显著提高合金的抗再结晶和抗高温软化的能力,Cu-0.1Ag-0.2Zr合金的强化机制是Ag的固溶强化、预冷变形引入的亚结构强化和铜锆化合物粒子的析出强化。更多还原

【Abstract】 A series of high-performance copper alloys including Cu-2.5Fe-0.03P,Cu-0.1Fe-0.03P,Cu-Ag-Cr and Cu-Ag-Zr were investigated incorporating work supported by National Defense Basic Research Project entitled "Basic research of special copper alloy materials for E-military project and preparation technology" and National Natural Science Foundation Project called "Existing forms and mechanisms of trace Ag,Zr and rare earth in high-strength, high-conductivity Cu alloy".For Cu-0.1Fe-0.03P copper strips,we have studied their mechanical properties and electrical properties and their microstructures were examined by OM,X-ray diffraction and electronic microanalysis.For Cu-2.5Fe-0.03P alloys,we have studied their structure changes under different aging and heat treatment processes.Furthermore, the influence the addition of trace amount of Ag,Cr,Zr and thermo-mechanical treatment on strength and electrical conductivity of Cu-Ag-Cr and Cu-Ag-Zr alloys were conducted.The main results out of this work are summarized as the follows:1.The existence of phosphor promoted hydrogen absorption during melting of Cu-0.1Fe-0.03P alloys through deoxidization. Hydrogen-riched pores gathered and grew up under external stress during hot rolling to form bubbles leading to surface defects for oxidizing gas transport and penetration underneath and facilitate the formation of Cu₂O inside the alloy.The brittle Cu₂O was either broke up or underwent deformation under pressure and migrated to the surface during cold-rolling and final rolling processes.Since the bond between Cu₂O and copper matrix was relative weak,micro-cracks often occurred at their interfaces during cold rolling.The expansion of micro-cracks and the break up of bubbles with continuous deformation eventually resulted in surface peeling of Cu-0.1Fe-0.03P alloy.2.The optimal thermo-mechanical treatment condition for Cu-0.1Fe-0.03P alloy strips was found out to be such that in situ solution treatment before 95%cold rolling and followed by aging at 500℃for 2h. The corresponded tensile strength,yield strength,elongation and electrical conductivity are 258MPa,192MPa,22.5%and 86%IACS respectively.Their microstructure is consisted of solid solution matrix and dispersed secondary phase particles such asγ-Fe,Fe₃P and Fe₂P.The main strengthening effect came from substructure and precipitation strengthening.3.The results of pole figure and ODF analysis show that The major texture of Cu-0.1Fe-0.03P alloy product sheet is {110}＜112＞brass texture,the minor textures are {110}＜100＞gauss texture,{123}＜634＞S texture and {001}＜100＞cubic texture.The crystal texture should be responsible for in-plane mechanical anisotropy of the product sheet.4.Compared with traditional processing methods,the combination of horizontal continuous casting and cold rolling and annealing offers shorter process time,lesser investment,lower cost,higher yield,and faster construction etc..Alloy strips prepared by this method have lower tensile strength,lower electrical conductivity,lower softening temperatures and higher elongations.However,the strips made by this new method（without hot rolling as did in the traditional methods） showed larger shrinkage defects during solidification which led to ablation and scale peel of during cold rolling.5.Utilizing traditional processing（hot rolling before solution treatment prior to cold rolling and aging）,iron and phosphor exist in the form of singly atomic Fe and Fe₃P compound.Besides Sub-structure strengthening came from the thermo-mechanical treatment,precipitation hardening of Fe₃P and the formation of Fe particles led to high strength6.Equation of kinetic of Phase-change/transition/transformation for aging process of Cu-2.5%Fe-0.03%P alloy can be deduced by the variation of conductivity as a function of time.For example, f=1-exp(-0.14749t^0.52564) at 550℃.7.The tensile strength,yield strength,elongation and electrical conductivity of Cu-0.1Ag-0.5Cr Strips treated at 950℃/1h and 30% pre-cooling deformation and 450℃/4h aging are 397MPa,335MPa, 14.8%and 77.5%IACS respectively.Addition of trace amount Ag exists mainly in solid solution while that of Cr as singly Cr particles.The main hardening mechanism is due to Ag solution,sub-structure strengthening and Cr particles precipitation.8.The optimal processing for Cu-0.1Ag-0.2Zr alloy is 950℃/1h solution and 30%pre-cooling deformation and 450℃/4h aging.The tensile strength,yield strength,elongation and electrical conductivity for the strip made this way are 373MPa、327MPa、10%and 95.7%IACS respectively.Addition of trace amount of Zr exists mainly as Cu-Zr compound particles.The appearance of these particles retards recovery and recrystallization significantly.The strengthening mechanism is solid solution strengthening of Ag,sub-structure strengthening produced by the pre-cooling deformation and precipitation strengthening of Cu-Zr particles更多还原