形变及热处理对Cu-Ag合金性能的影响

本文通过对Cu-Ag合金进行大形变量拉伸及热处理,制成具有高强度、高导电率的纤维增强复合材[1].在此基础上,研究了形变及热处理对Cu-Ag合金力学性能、电学性能的影响.并通过对Cu-Ag合金初态、终态组织的分析,初步解释了其中的强化机理.     

形变原位Cu-Ag复合材料的研究进展

高强高导Cu-Ag合金是一种具有优良物理性能和力学性能的结构功能材料,具有强度和导电率的良好匹配。从合金的组织、制备工艺、强化机理及导电机理等方面综述了Cu-Ag合金的研究现状,并指出了其进一步发展的前景。     

Cu-Ag合金原位纤维复合材料研究现状

凝聚态物理、材料科学、化学和生物科学的研究需要用到强磁场技术,铁磁线圈是强磁场装置(特别是脉冲强磁场装置)的基础部件,由高导热性、高导电性和高强度的材料组成,Cu-Ag合金原位纤维复合材料应运而生,其相关报道最早可追溯到20世纪六七十年代。Cu-Ag合金原位纤维复合材料是一种纳米晶双相复合材料,较单相材料具有更高的强度和热稳定性,同时还具有较强的导电性能。经过半个世纪的发展,Cu-Ag合金原位纤维复合材料的应用范围扩展到框架材料、接触线及接头等,Ag含量由最初的80%降低至10%～30%(均为质量分数),成本显著降低,且具有相当的电学和力学性能。在此期间,大塑性变形过程中组织形态结构的演变、相界面、相间距及尺寸等对性能的影响已经得到了较充分的研究,并且能通过热处理技术调和变形过程中强度上升而电导率下降的矛盾;研究者们还通过加入Cr、Nb、Zr、Y、Gd、Ce等第三甚至第四组元进行微合金化,在替代Ag的同时产生更多对合金有益的作用,以期进一步提高强度、塑性等综合性能,并取得了一定成效。但早期的研究还存在一些不足:(1)未从更微观的角度进行更深入的研究;(2)传统的多道次塑性加工技术流程较长;(3)性能预测理论模型的普适性不够。因此,近七年来除更全面深入地研究拉拔、轧制及热处理等工艺外,对Cu-Ag合金原位纤维复合材料的探索主要聚焦于磁场下定向凝固、大塑性变形制备工艺、更低的Ag含量及添加其他合金元素对其性能的影响,以及引入先进分析表征技术。研究发现磁场下定向凝固可改变晶体的生长方式,通过对枝晶大小和间距、共晶组织体积分数等进行控制来影响材料的性能,使强度进一步提高。等通道转角挤压(Equal channel angular pressing,ECAP)及高压扭转(High-pressure torsion,HPT)等大塑性变形技术在Cu-Ag合金上也得到了应用,使晶粒进一步细化,塑性等综合性能得到提高,为短流程制备Cu-Ag原位纤维复合材料提供了方向。通过对制备技术及微合金化的深入研究,目前Cu-Ag原位纤维复合材料中的Ag含量已经可降低到10%(质量分数)以下,且6%Ag含量的铜基原位复合材料在日本已经被成功应用于强磁场技术中。此外,从更微观的原子/分子角度,研究者揭开了位错、孪晶、织构在制备过程中的产生、演变及对性能的影响规律。本文从Cu-Ag原位纤维复合材料的力学与电学性能、强度与电导率的匹配关系展开讨论,综述了这一领域的研究现状,并探讨了其发展前景和目前存在的问题。     

高强高导铜银合金的研究现状及发展趋势

Cu-Ag合金作为先进的导体材料,广泛应用于微电子、交通、航空航天及机械制造等工业领域。回顾了近年来高强高导Cu-Ag合金的主要研究进展。针对Cu-Ag合金的导电性和力学性能,主要从合金设计中的Ag成分设计、微合金化和加工工艺中的制备方法、热处理及变形处理等方面进行评述。分析了Cu-Ag合金的成分设计原则,比较了上述几种加工工艺的特点,并提出大塑性变形将会是一种非常有前景的制备高强高导Cu-Ag合金及其它合金的加工工艺。最后指出了现阶段研究中存在的问题及未来发展的趋势。     

新一代国产化高速铁路接触线的研究与开发

在分析国内外高速电气化铁路接触网用接触导线的使用现状及发展趋势的基础上,建议我国应尽快研制国产铜合金接触线,以加速高速铁路接触线国产化的进程.进一步指出时效强化型铜合金Cu-Ag、Cu-Cr合金,可通过添加微量合金元素Cr、Zr,使其导电率大于80%IACS,强度达到600MPa,作为接触导线的理想材料.     

Cu-10Cr-0.4Zr原位复合材料的微观组织与性能

制备了Cu-10Cr和Cu-10Cr-0.4Zr合金,并经冷变形形成了原位复合材料,观察了Zr的添加对合金铸态组织、复合材料的纤维形貌,研究了Zr的添加和冷变形率对拉伸强度以及导电率的影响.研究表明,在Cu-10Cr合金中添加的0.4%Zr,Cr析出相的直径由15～80μm细化到10～20μm;在相同的冷拔应变下,Cu-10Cr-0.4Zr复合材料较Cu-10Cr材料具有了更高的基体晶格阻力、更加细小均匀的纤维相以及纤维间距,使得Cu-10Cr-0.4Zr复合材料的强度更高.当冷拔应变达到6.2时,Cu-10Cr-0.4Zr原位复合材料抗拉强度高达1089MPa,而Cu-10Cr材料的抗拉强度仅为887MPa.在相同冷拔应变下,Cu-10Cr材料的导电率比Cu-10Cr-0.4Zr材料中的导电率略高.随着材料冷拔应变的增加,决定复合材料电阻率的基体材料内位错散射电阻转变成界面散射电阻,复合材料的电导率逐渐下降.     

高强高导电铜合金耐蚀性研究

采用乙酸盐雾试验和电化学方法对Cu-Ag和Cu-Fe-P两种高强高导电铜合金的腐蚀行为进行研究。通过SEM,EDS和XRD等方法分析合金的腐蚀形貌及腐蚀产物的组成。研究表明:Cu-Fe-P合金比Cu-Ag合金有更好的耐蚀性能。微量Fe和P的同时加入,可以综合利用Fe的细化晶粒和P的脱氧作用,细化和净化合金组织,在提高合金强度和电导率的同时改善合金的耐蚀性。     

高导电铍铜合金及其组织与性能的研究

本文研制了高导电铍铜合金(Cu-2.5％Ni-0.5％Be),并对该合金和 C17500合金(Cu-2.5％Co-0.5％Be)的组织、性能及强化机制进行了研究。CuNiBe合金经热处理后的最佳性能达到σ_b=1000MPa,电导率为48％IACS。CuCoBe合金最佳性能达到σ_b=980MPa,电导率为43％IACS。结果表明,CuNiBe合金可代替CuCoBe合金。CuNiBe合金的时效强化相为NiBe相,CuCoBe合金的强化相为CoBe相。固溶处理后的冷变形促进了时效过程,使析出相更加弥散,同时使合金在时效过程中发生再结晶,细化了合金晶粒,使合金强度提高,导电性也得到改善。本文给出了合金的最佳热处理规范,以便在生产中采用。     

高强高导铜(合金)基复合材料强化与物性研究进展

从材料强化和物性研究两方面综述了国内外高强高导铜(合金)基复合材料的最新研究进展.评述了各种强化方法:沉淀强化、细晶强化、相变强化、形变强化、弥散强化和第二相强化.介绍分析了复合材料制备的各种工艺方法:液固两相铸造复合工艺、SHS法、半固态凝固法、粉末冶金法和复合电沉积法.归纳了影响导电性能的因素:合金元素的种类、含量和相结构.最后讨论了该类材料的研究及发展趋势.     

热处理对Cu-Ag合金原位复合材料结构与性能的影响

采用原位复合技术制备了Cu-10Ag合金原位复合材料,研究了热处理对形变复合材料的结构与性能的影响.热处理促使Ag沉淀析出和晶格常数降低.中间热处理增大极限拉伸强度(UTS)与改善导电率.采用不同的热机械处理获得了由不同强度与导电率组合的综合性能,典型的性能达到强度1500～1560MPa和导电率62%IACS～64%IACS.真实应变η=9.8的大变形Cu-10Ag合金原位复合材料的再结晶温度约350℃,其性能直至300℃是稳定的.自然时效处理提高大变形原位纤维复合材料的强度3.5%～5%,降低再结晶温度至250℃.     

Comparison of microstructure and strength in wire-drawn and rolled Cu-9 Fe-1.2 Ag filamentary microcomposite

Comparison of microstructure and strength of Cu-9 Fe-1.2 Ag microcomposite wires and sheets obtained by cold drawing or cold rolling combined with intermediate heat treatments has been made. The primary and secondary dendrite arms are aligned along the drawing or rolling direction and elongated into filaments after cold working. The microstructural scale of wire-drawn microcomposites was found to be finer than that of rolled microcomposites at the same drawing strain. The more effective microstructural refinement induced by unidirectional metallic flow and co-deformation of filament and Cu matrix resulted in finer microstructure in microcomposite wires. The ultimate tensile strength and the conductivity of wire-drawin Cu-Fe-Ag microcomposite were higher than those of rolled Cu-Fe-Ag microcomposites. The strength of Cu-Fe-Ag microcomposites is dependent on the spacing of the Fe filaments in accord with a Hall-Petch relationship. The good mechanical and electrical properties of wires may be associated with the more uniform distribution of fine filaments. The fracture surfaces of Cu-Fe-Ag wires and sheets showed ductile-type fracture and iron filaments were occasionally observed on the fracture surfaces. The fracture surface of Cu-Fe-Ag wires showed generally finer microstructural morphology than that of Cu-Fe-Ag sheets, consistent with the finer microstructural scale in Cu-Fe-Ag wires.     

Mechanical and electrical properties of heavily drawn Cu-Nb microcomposites with various Nb contents

The mechanical and electrical properties of Cu-Nb filamentary microcomposite fabricated by the bundling and drawing process were examined. The strength increased gradually with increasing Nb content while the ductility was insensitive to Nb content. The ratios of yield stresses are found to be close to that of Young's moduli in various Cu-Nb microcomposites, suggesting that athermal obstacles primarily control the strength. The fracture morphologies show ductile fractures irrespective of Nb contents. Secondary cracking along the interfaces between subelemental wires was occasionally observed and the frequency of secondary cracking increased with increasing Nb content. The conductivity and the resistivity ratio (_{295 K}/_{75 K}) decreased with increasing Nb content. The decrease of the conductivity and the resistivity ratio can be explained by the increasing contribution of interface scattering.     

Influence of Aging Treatment on the Mechanical and Electrical Properties of Cu-0.5%Be Alloy

The influence of aging treatment on the microstructure,mechanical properties and electrical conductivity of Cu-0.5 wt pct Be alloy for connector material applications was investigated.The properties of mechanical strength and electrical conductivity increase with increasing aging temperature and time.Microstructure of the aged Cu-Be alloy revealed that grain size and fraction of low angle and high angle grain boundary were not greatly changed;however,transmission electron microscopy （TEM） analysis exhibited that beryllides precipitation （CoBe and NiBe） with a size of 50 nm were distributed in grains.It was,therefore concluded that these beryllide precipitates improved the mechanical strength and also it was favor in improvement of electrical conductivity.     

Copper–Iron Filamentary Microcomposites

The Cu–Fe system is of particular interest because of the relatively low cost of Fe compared to other insoluble BCC phases such as Nb, Mo, Cr, and Ta. The relatively high solubility of Fe in Cu at high temperatures, coupled with the slow kinetics of Fe precipitation at low temperatures is, however, known to reduce electrical conductivity. The key to improving strength/conductivity properties is to reduce the initial dendrite size and to precipitate Fe effectively in the Cu matrix. Thermomechanical treatments have been employed by some investigators to optimize the strength and conductivity of Cu–Fe microcomposites. The study also shows that refinement of dendrites and easier nucleation of precipitates by the addition of third alloying elements can lead to improved strength/conductivity properties of Cu–Fe microcomposites.     

Mechanical and Electrical Properties of Cryo-worked Cu

For manufacturing the magnets of fusion machines pure copper of both high mechanical resistance and electrical conductivity is required. Though high purity copper guarantees high electrical conductivity, its mechanical properties may be not suitable for the applications in tokamaks. In this view, a new procedure developed for obtaining high purity copper with excellent mechanical strength is described in this work. Samples of oxygen free copper (OFC) have been worked by pressing in liquid nitrogen (77 K). It has been verified that the mechanical properties of the worked metal are strongly dependent on the strain rate. Very low strain rates permitted to attain values of tensile yield strength (550 MPa) significantly higher than those obtained by traditional cold-working at room temperature (450 MPa). The electrical conductivity of the cryo-worked Cu decreases with the tensile yield strength even though the hardest samples of tensile yield strength of 550 MPa exhibit still acceptable values of conductivity (about 94 % IACS at room temperature).     

多级时效热处理对7056铝合金析出组织与耐蚀性的影响

利用透射电子显微镜(TEM)、扫描电子显微镜(SEM)、力学性能测试、电导率测试以及剥落腐蚀、慢应变速率拉伸应力腐蚀(SSRT)、Tafel循环极化曲线等手段研究多级时效热处理对7056铝合金析出组织及耐蚀性的影响。结果表明:过时效再时效热处理后溶质原子二次析出,晶内析出相体积分数增大,晶界析出相粗化断开,无沉淀析出带宽化。与120℃/24h相比,采用120℃/6h预时效工艺有利于晶内细小析出相回溶和粗大相长大。再时效热处理可提高过时效合金的强度和电导率,与峰时效和回归再时效相比,合金的抗拉强度损失不大,电导率明显提升。过时效再时效热处理后,合金晶界处连续阳极溶解被有效避免,抗剥落腐蚀和抗应力腐蚀性能增强。     

Cement-based composites containing functionalized carbon fibers

Carbon fibers can be used to improve both mechanical properties and electrical conductivity of cement, allowing the preparation of a strengthened and toughened cement that can be used for self-monitoring applications. To guarantee both a good dispersion in water and a strong interaction with cement, surface functionalization of carbon fiber surface by reaction with acid was preferred to the use of a dispersing agent. The best oxidation conditions were chosen by using a Taguchi approach, and the samples contained the treated fibers were subjected to both mechanical and electrical tests, to determine flexural strength, toughness, compressive strength and electrical conductivity. It was shown that a not-too-strong oxidation by piranha solution was very effective to obtain well-dispersed fibers and a cement-composite with improved mechanical properties (in particular toughness) and electrical conductivity.     

Aging Strengthening in Rapidly Solidified Cu-Cr-Sn- Zn Alloy

It is known that the strength of alloys can be successfully improved by rapid solidification. The paper presents a process where Cu-Cr-Sn-Zn lead frame alloy is produced by rapid solidification and aging. The microcrystalline structure of rapidly solidified Cu-Cr-Sn-Zn alloy is smaller grain structure examined by optical metallography. The effects of aging processes on the microstructure and properties of the lead frame alloy were investigated. Aged at 500°C for 15 min the fine coherent precipitates Cr dist...     

Enhanced mechanical properties and electrical conductivity in ultrafine-grained Al alloy processed via ECAP-PC

The objective of this work is to study the effect of grain refinement using equal channel angular pressing with parallel channels (ECAP-PC) on microstructure, mechanical properties, and electrical conductivity of an Al–Mg–Si alloy. The coarse grained (CG) material is subjected to ECAP-PC processing at 100 °C for 1, 2, and 6 passes. Mechanical behavior of the Al–Mg–Si alloy after ECAP-PC processing and its electrical conductivity are analyzed with respect to the microstructure developed during ECAP-PC processing. The effect of artificial aging (AA) on the microstructure, mechanical properties, and electrical conductivity of the ECAP-PC processed Al–Mg–Si alloy is investigated. It is shown that the microstructure developed during ECAP-PC processing affects the kinetics of the aging process that, in turn, affects the mechanical properties and electrical conductivity of the material. It is demonstrated that both mechanical properties and electrical conductivity of the Al–Mg–Si alloy can be simultaneously enhanced via intelligent microstructural design through optimization of the thermo-mechanical processing applied to this material.     

Y对耐热铝导体材料铸态组织和性能的影响

随着特高压输电技术在我国的大力发展,铝合金导体材料作为特高压输电线路的主要组成部分,受到业内的广泛关注.本文采用电导率测试、硬度测试、金相显微镜和扫描电镜观察等手段,研究添加不同含量稀土Y对铸态Al-Zr耐热铝导体材料的影响.研究结果表明:Y元素和Fe、Si等杂质元素形成金属间化合物,可净化基体,改变杂质相的形态和分布,使其粒子化、球化和细化.Y元素在枝晶网络和晶界分布,从而细化晶粒和枝晶组织,但添加量达到0.5%时晶粒细化不均匀.当Y含量为0.2%时,电导率达到60%IACS;当Y含量为0.3%时,硬度达到最高值20.9HBS,且电导率并无明显下降.加入0.3%Y可使耐热铝导体材料获得较好的综合性能.