【作者】 秦永强；

【导师】 吴玉程； 黄新民；

【作者基本信息】 合肥工业大学 ， 材料学， 2013， 博士

【摘要】 近年来随着电子、电力等行业的迅猛发展，相关企业对铜合金的强度和导电性能提出了更高的要求，但是我国研发生产的高强度高导电铜合金的性能与国外存在巨大差距，因此如何获得高强度高导电铜合金成为当前铜合金研究与开发的首要任务。铜-铬-锆系合金是目前最具有潜力满足高强度高导电需求的铜合金材料。本文运用正交设计的方法对高强度高导电铜-铬-锆合金成分进行了优化设计，围绕铜-铬-锆合金的高强度高导电性能进行了系统研究，首先，研究了铜-铬-锆合金的制备技术，以及中间合金的制备方法；其次，探讨了铜-铬-锆合金力学性能、导电性能与固溶、变形、时效工艺的关系及铜-铬-锆合金的组织结构演变过程；进一步提出了低温快速变形处理合金的方法，并分析了低温快速变形对铜-铬-锆合金性能的影响；另外，针对加工过程中出现的残余应力问题，探讨了消除和控制残余应力的工艺；最后，针对所研究合金材料的具体焊接使用过程中可能存在问题和具体温度场分布情况等进行模拟研究。有关研究内容、实验结果和结论如下：（1）通过理论计算设计了合金的成分区间，运用正交设计的方法优化了合金的成分；研究了中间合金的制备方法、合金熔炼工艺、浇铸工艺，并研究了合金后续处理工艺包括扩散退火工艺、热轧变形量、在线固溶处理工艺、时效工艺；随后介绍了合金组织和性能的表征手段和设备；结合对熔炼获得的合金的导电性能和抗拉强度的测试结果进行了正交实验分析，提出最佳的合金成分配比方案为Cu-1.4Cr-0.12Zr。（2）研究了固溶、变形和时效工艺对合金抗拉强度和导电率等性能的影响，用正交实验法探讨了高强度高导电铜-铬-锆合金的固溶、变形和时效工艺的最佳参数。结果表明：固溶温度对合金的导电性能的影响最大，但固溶强化作用对合金抗拉强度的影响比较小；轧制形变量的增大对合金导电性能的影响不大；时效温度与时效时间的增加有助于合金导电性能的回复，但时效再结晶所导致的织构度减小会大大降低合金的抗拉强度；合金的最优处理工艺为920℃固溶处理+80%轧制变形+450℃时效处理1h。所得的Cu-1.4Cr-0.12Zr的导电率为87.05IACS%，抗拉强度为559.86MPa，延伸率为9.02%。（3）使用金相显微镜、SEM、XRD、TEM等手段，对合金不同状态的组织结构进行了表征，探讨了高强度高导电铜-铬-锆合金的组织演变的过程。结果表明：在1180±30℃熔铸温度下铜-铬-锆合金的铸态显微组织较为弥散、均匀，为后续的热处理和加工提供良好的组织准备；合金在950℃固溶1h水冷的固溶效果较好，在450℃时效时，已出现再结晶现象，时效时间过长或时效温度过高会使再结晶形核进一步扩展，这与第三章的分析结果一致；随着扩散退火、固溶、时效工艺的进行，铜-铬-锆合金析出相依此由CuZr₂H_x析出相→CuZr₂析出相→Cu5Zr析出相演变，最终形成弥散、均匀的Cu5Zr析出相，这种变化将在合金基体中产生了更多的强化相支点，有利于合金的强化。（4）首次提出低温快速变形处理铜-铬-锆合金的方法，分析了不同温度和不同变形量对低温快速变形处理后合金性能的影响，讨论了合金的微观结构与合金性能变化的关系，并对低温快速变形后合金的微观结构进行了讨论。结果表明：对合金进行低温快速变形可以实现孪生强化的效果；随着变形量的增加，铜-铬-锆合金晶粒位相差减小，以小角度晶界为主；低温快速变形处理后，铜-铬-锆合金织构类型由{110}<112>转变为{110}<001>型和{110}<001>型织构，金相观察和TEM观察均表明在合金基体中产生了大量的孪晶，同时合金导电率下降较少，强度获得了一定的提升，有利于获得导电性能与强度都比较好的合金。（5）结合铜带材处理工艺过程中合金板带产生残余应力的问题，利用XRD研究不同状态和不同退火时间下铜-铬-锆合金的应力情况，研究了铜-铬-锆合金的残余应力消除及控制技术。（6）采用有限元模的方法对铜-铬-锆合金材料的焊接工艺进行了探索，利用ANSYS软件对合金平板焊接过程的三维动态温度场、应力场进行了数值模拟，研究了合金温度场变化规律和熔池形状，以及焊接过程中不同时刻的应力变化规律和残余应力的分布规律，重点分析了焊缝中心线上的纵向应力。结果表明：焊接开始到5s时合金板材温差较大；焊接完毕10s后整个板材温度趋于一致，且温差控制在10℃内；80s后温差控制在1℃内，并且冷却过程中越接近室温，冷却速度越慢。焊接过程中，靠近焊缝一侧高温区受到纵向热压力作用，而在远离焊缝一侧受到纵向热拉应力的作用；焊接完毕，板料自然冷却，在近焊缝区段产生拉应力，在稍远区段产生压应力。这一研究成果对铜-铬-锆合金材料焊接工艺的优化具有重要指导意义。更多还原

【Abstract】 Up-to-date, the production and consumption of copper and its alloys in China is the largest allaround the world. There is a significant demand of high-performance copper alloys for thedevelopment of electronics, power industry and so on. Nowadays, the overproduction of low-gradecopper alloy products results in the abnormal competition in domestic markets. Compared withGermany, the United States, Japan and other developed countries, there is still a large disparity onthe scientific research and industrial production of high-performance copper alloys. Now all theabove situations have been a serious threat to the survival of the copper industry, as well as a seriousimpediment to the development of many other related industries. Therefore, research anddevelopment of high-performance copper alloys has become the primary task for the domesticcopper industry. In order to overcome this obstacle, this thesis focused on the research ofhigh-strength and high conductivity copper-chromium-zirconium alloys.In this thesis, orthogonal design method was adopted for the composition design of high-strengthand high-conductivity copper-chromium-zirconium alloys. The mechanical performance andelectrical conductivity of the high-strength and high-conductivity copper-chromium-zirconiumalloys were firstly systematically studied. Several preparation techniques were explored for thepreparation process of copper-chromium-zirconium alloys and master alloys. Relationships betweenmechanical properties, electrical properties and processing parameters were investigated. The phasetransition process was also characterized. Fast deformation treatment with ultra-low temperature wasdeveloped during the experiments, which proved to influence significantly on the mechanical andelectrical properties of the as-prepared copper alloys. Finite element simulation was finallyintroduced for the residual stress reduction and control technology during the production process andwelding process of copper-chromium-zirconium alloys. The main results are as follows.（1） With theoretical calculation, the composition range of copper-chromium-zirconium alloys wasdeveloped through orthogonal design method. And we selected9kinds of composition ratio for thefollowing experiments. Master alloys were introduced in our experiment and then melt together withthe copper matrix in the vacuum induction melting furnace. The final state performance of theas-designed9kinds of alloys were characterized and orthogonally analyzed. The best of the alloycomposition components should be Cu-1.4Cr-0.12Zr.（2） Solid solution treatment, deformation and aging process were carried out for the as-preparedcopper alloys. And the best parameters of solid solution, deformation and aging process wereobtained. The solution temperature had a serious influence on the conductivity of copper alloys. Butthe strengthening effect of solid solution on the tensile strength of the alloys was relatively small.The rolling deformation presented a slight influence on the conductive properties of the copperalloys. The increase of aging temperature and aging time was benefit for the alloy conductivity,which would simultaneously reduce the tensile strength of the alloys. The optimal treatment processwas done with solution treatment at920℃, rolling deformation percent80%and aging time onehour at450℃. After the best-choice treatment, the electrical conductivity87.05IACS%。 Thetensile strength and elongation ratio were559.86MPa and9.02%, separately.（3） The phase evolution process of high-strength an high-conductivity was characterized bymetallurgical microscopy, SEM, XRD and TEM. The microstructures and properties of alloys withdifferent state were also characterized for the investigation of phase transition during thedeformation and annealing process. The results indicated that the microstructure of Cu-Cr-Zr alloyswas dispersed distributed uniformly smelt at1180±30℃, which was beneficial to the following heat treatment and process. In addition, better properties of alloys were achieved after solid solutiontreatment at950℃and then quench in water for1h. When aging at450℃， recrystallizationappeared and the nuclei further expanded with long aging time or high aging temperature, which wasin accordance with the results in Chapter3. After successive diffusion annealing treatment,solidsolution treatment and aging treatment, phase evolution of precipitates was obtained in turn CuZr₂H_x→CuZr₂→Cu5Zr in the aforementioned treatment. And finally, dispersively and uniformlydistributed precipitate Cu5Zr was achieved, this provided more reinforced phase in the copper matrix,which was in favor of getting alloy with high strength.（4） Low temperature and fast deformation processing was employed to investigate treatment andproperties of Cu-Cr-Zr alloys. Relationship between microstructure and properties of alloys wasstudied and the microstructure change after low temperature and fast deformation was also discussed.The results presented that twin strengthening was an effective approach to enhance the strength ofalloys,meanwhile, it was not harmful to the conductivity of alloys. With the increase of deformationamount,phase difference of grain in the Cu-Cr-Zr alloy decreased dominated by small-angle grainboundaries. The textures transformed from {110}<112> to {110}<001> and {110}<011> after lowtemperature fast deformation. Metallurgical microscopy and TEM observation suggested that therewere a great amount of twins in the alloy matrix, although the conductivity of the alloy decreasedslightly, the strength of the alloy improved a lot.This was beneficial to get alloys with goodconductivity and strength.（5） We described the reduction of residual stress and control technology of the copper strips basedon the problems encountered in the production process in Tongling Nonferrous Metals JinweiCopper Co., Ltd. Through the strict control of the quality of the manufacturing process, includingequipment cleaning, liquid reagent concentration and process parameters of the trial, surface qualitycould be achieved with no scratches, oxidation, stains and other defects. The surface roughnessvalues were0.1μm-0.2μm, which could meet surface requirements of the high-precision frame stripalloys.（6） Finite element simulation was conducted for the welding process ofcopper-chromium-zirconium alloys. The thermal parameters of welding process were taken intoaccount as non-linear relationships. The three-dimensional dynamic temperature field and stress fieldof welding process were simulated using ANSYS software. The temperature field and melting poolshape were studied with different stress variation and residual stress distribution during the weldingprocess. The longitudinal stress along the center of the weld line was stressed during our experiment.The results showed that there was obvious temperature difference on the welding plate for thestarting5seconds. When the welding was completed, the plate temperature became the same onlyafter10seconds.80seconds later, the temperature variation was only1℃. The closer to roomtemperature, the slower cooling process was. During the welding process, there was longitudinalthermal pressure for the high-temperature region close to the weld side; and there was thermaltensile stress for the other side away from the weld line. After welding treatment with self cooling,there was always tensile stress near the weld zone and compressive stress a little far from the weldzone.更多还原