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.     

Cu-15Cr-0.2Zr形变原位复合材料强度和导电性研究

采用冷变形＋适当的中间热处理的方法制备了Cu-15Cr-0.2Zr形变原位复合材料，并研究了微量盈对Cu-15Cr原位复合材料组织和性能的影响。结果表明：合金经室温变形后，Cr相转变成弯曲薄片状纤维，随着应变量的增加，合金的强度提高，导电率下降。添加0．2％盈使Cu-15Cr-0.2Zr在η=6．438时的极限抗拉强度达到1072MPa，导电率达到68.7％IACS。     

Cu-10Cr-0.4Zr形变原位复合材料的组织演变特征

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。研究Zr添加剂对合金铸态组织和复合材料的纤维形貌的影响,以及随着形变率的提高β-Cr纤维演变特征。研究表明,在Cu-10Cr合金中添加的0.4%(质量分数)Zr,Cr析出相的直径由15~80μm细化到10~20μm;对Cu-10Cr-0.4Zr合金能谱分析表明,在Cu-10Cr-0.4Zr铸态组织中存在Cu5Zr相的形成和析出;随着形变率增大,β-Cr相之间的间距不断减小,其宽厚比也进一步增大,纤维相发生比较明显的弯曲和扭折,特别是当形变率η=6.2时,纤维相的厚度能够达到250~350nm,纤维相变形和分布也趋于均匀;当η=6.2时,Cu-10Cr-0.4Zr形变复合材料的抗拉强度达到1089 MPa,采用改进的Hall-Petch公式计算其值为1037 MPa,理论计算数值与观测结果基本一致。     

形变Cu-11Cr-0.07Ag原位复合材料的组织和性能

采用熔铸-中间热处理-变形工艺制备了形变Cu-11Cr-0.07Ag原位复合材料, 利用扫描电镜、数字微欧计及液晶电子拉力试验机研究了材料的微观组织、力学性能和导电性能。结果表明: 随着冷加工变形量的增加, 铸态无序分布的Cr枝晶状组织逐渐转为沿线拉方向排列, 形成定向排列的Cr纤维, 抗拉强度大幅提高, 电导率略有下降。经适当冷加工变形和中间热处理后的形变Cu-11Cr-0.07Ag原位复合材料具有较好的强度和电导率匹配。冷加工变形量为8时, 其抗拉强度和电导率分别达到851 MPa和73.9% IACS。     

高强高导Cu-Cr-Zr合金的微观组织与性能

Cu-Cr-Zr合金是电气化铁路接触网装备的重要材料,其抗拉强度和导电率性能要求较高。采用高频熔炼、铜模快冷、固溶处理、冷轧和退火处理制作了Cu-Cr-Zr合金样品,分析了其显微组织、抗拉强度和导电率之间的关系。在铜晶粒内部和晶界上析出的第二相Cu5Zr和其他多元化合物是Cu-Cr-Zr合金获得高强度的主要原因。固溶体中的Cr、Zr溶质含量是影响合金电阻率的主要因素,纳米及亚微米级的第二相可使合金获得较好的强度和导电性。冷轧后试样经过450℃、550℃退火处理,发现550℃退火处理后Cu-0.7Cr-0.4Zr合金的抗拉强度可达550MPa,导电率达82.5%IACS。     

Cu-15Cr-0.1Zr原位复合材料中纤维相的组织演变

通过感应熔炼、铸造、锻造和冷拔变形制备了Cu-15Cr-0.1Zr原位复合材料.采用SEM和TEM观察分析纤维相组织形态的演变.在较低的应变量下纤维保持着与铸态树枝晶相同的bcc单晶结构,在较高的应变量下,单根Cr纤维被分隔为一些由亚晶界组成的亚结构,相邻亚晶的偏差角在5～30°之间.     

冷轧板条马氏体组织与力学性能研究

将低碳钢(10#)淬火获得低碳板条马氏体组织,然后进行多道次冷轧变形,制备具有超高强度的低碳钢板材,研究其力学性能的变化规律,并利用金相显微分析和扫描电子显微分析方法观察其显微组织演变与断口形貌。实验结果表明,淬火获得的具有马氏体组织的低碳钢(10#)抗拉强度超过1. 3 GPa,仍能保持较好的塑性(延伸率约为15%),随着冷轧变形量的增加,材料的强度和硬度显著增大,而塑性逐渐降低,当冷轧变形量大于30%后,断后延伸率低于10%。当冷轧变形量达到80%时,硬度从440HV(未变形)增加到532HV,抗拉强度超过2. 0 GPa;随着变形量的增加,冷变形马氏体板条间距减小,变形组织与轧制方向趋于平行排列,逐渐呈现分层特征。随着冷轧变形量的增加,断口中心韧窝和空洞数量减少,而且韧窝的尺寸和深度减小,空洞相互连接,裂纹萌生,断口处出现了明显的分层裂纹和撕裂状的结构,当变形量超过50%时,断口处的分层结构和撕裂状的裂纹开始显现。     

Ni、Si元素配比对Cu-Cr-Zr合金组织与性能的影响

在Cu-Cr-Zr合金中添加Ni、Si元素,制备Cu-0.6Cr-0.15Zr、Cu-2.8Ni-0.7Si-0.6Cr-0.15Zr(w(Ni)/w(Si)=4∶1)、Cu-2.8Ni-0.9Si-0.6Cr-0.15Zr(w(Ni)/w(Si)4∶1)、Cu-2.8Ni-0.56Si-0.6Cr-0.15Zr(w(Ni)/w(Si)4∶1)共4种合金。研究了Ni、Si元素及其配比对合金组织及性能的影响。结果表明:Ni、Si元素细化了合金组织,增强了合金高温力学性能。合金时效初期先析出CrSi2化合物,时效后期析出相颗粒主要有CrSi2、Ni2Si、ZrCrSi2,形态为长条形、椭圆形及圆盘状。时效处理后,与Cu-0.6Cr-0.15Zr合金相比,加入Ni、Si元素后合金硬度从131HV上升到240HV以上;导电率从88%IACS左右降到40%IACS左右。Ni、Si元素配比对导电率的峰值影响有限,在4%IACS~9%IACS;对硬度峰值的影响在20HV~30HV之间。     

形变Cu-11.5 %Fe 原位复合材料的强度和导电性

研究了经多次冷拔或冷拔配合中间热处理制得的形变Cu-11.5 %Fe 原位复合材料的组织、强度和导电性。用SEM 和TEM 观察分析了材料的组织结构。结果发现, 形变量η ≥5137 的形变Cu-11.5 %Fe 原位复合材料的Fe 树枝晶已成为细纤维状, 在横截面呈薄片弯曲状。形变量越大, 纤维越均匀细化。力学性能和电阻率测试结果发现, 随形变量增加, 强度提高, 同时电阻率增大。中间热处理可在不损失强度的同时, 明显降低电阻率。经3 次中间热处理后, 不同形变量下的材料电阻率均可下降约4.4μΩ·cm。几个较好的电导率和极限抗拉强度组合为: 70.6 %/ 659 MPa (Φ0.8) 、64.6 %/ 752 MPa (Φ0.5) 和51.9 %/ 880 MPa (Φ0.2) 。      

冷轧变形对镀Ni-Co钢带耐腐蚀性能的影响

为了获得高性能的合金镀层薄膜材料,采用电沉积法制备了Ni-Co合金镀层薄膜,对镀层的钴含量、表面形貌及冷轧变形下的耐腐蚀性能进行了研究.结果表明:当镀液中硫酸钴含量为2 g/L时,合金镀层中的钴含量约为3.89%,镀层表面光亮、结晶致密;冷轧变形量为2%～4%时,镀Ni-Co合金薄膜钢带的耐腐蚀性能得到提高,变形量超过4%后其耐腐蚀性能降低.这说明小的冷轧变形能有效地提高镀层的耐腐蚀性能.     

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.     

Effect of doping with Zr on the properties of the deformation-processed Cu-Fe in-situ composites

Effect of doping with alloying element Zr on the structure, the electrical resistivity and the strength of deformation-processed Cu-Fe in-situ composites were studied respectively by scanning electron microscope (SEM), transmission electronic microscope (TEM), material test system (MTS) and resistance measuring apparatus. The experimental results show that the ultimate tensile strength (UTS) and the conductivity of Cu-11.5% Fe-Zr wire cold drawn to the drawing strain η = 7.57 with intermediate heat treatments were observed to be 824 MPa and 61.4% IACS respectively, and those of Cu-11.5% Fe were 752 MPa and 64.6% IACS. Doping Zr can improve the thermal stability of Cu-Fe composites. The strength of Cu-Fe-Zr wire does not drop more rapidly at higher annealing temperatures (above 300°C) than that of Cu-Fe wire.     

Microstructure, mechanical properties and electrical conductivity of industrial Cu-0.5%Cr alloy processed by severe plastic deformation

Microstructure, mechanical properties and electrical conductivity of industrial Cu-0.5% alloy subjected to equal channel angular pressing (ECAP) by route A and cold rolling with and without aging treatment were investigated. The lamellar grains in thickness of 100 nm were obtained after eight ECAP passes. They were not further pancake shaped, but fragmentary and obtained less sharp boundaries with more dislocations in addition to cold rolling. After aging at 450 °C for 1 h, high density of dislocations and some coarse grains were observable after ECAP and the additional cold rolling, respectively. The tensile tests show that tensile strength arrived at 460 MPa and 484 MPa after four and eight passes of ECAP, respectively, the corresponding tensile strength increased to 570 MPa and 579 MPa after the additional cold rolling. However, the electrical conductivity was not more than 35% IACS. It was proved that four passes of ECAP followed by 90% cold rolling and aging at 450 °C for 1 h offered a short process for Cu-0.5%Cr alloy to balance the paradox of high strength and electrical conductivity, under which the tensile strength 554 MPa, elongation to failure 22% and electrical conductivity 84% of IACS could be obtained. The high strength was explained by precipitation strengthening and fine grain strengthening.     

INFLUENCE OF AXISYMMETRIC DEFORMATION PROCESSING METHODS ON THE MECHANICAL PROPERTIES OF Cu-Nb COMPOSITES

It has been shown that deformation processed Cu-19% Nb alloys with good strength and electrical conductivity can be developed in sizes that are useful for engineering applications. Mot extrusion of bundled sub-elemental Cu-19% Nb wires followed by cold drawing to make a composite wire of diameter equal to that of the initial sub-elemental wires resulted in a 67% increase in the ultimate tensile stress. However, on subsequent cold drawing of this composite wire the strength increased at a slower rate than that obtained on continuing cold drawing of the sub-elemental wire and the strength differential decreased. In addition, after cold drawing to equivalent diameters the electrical conductivity of the composite wire was less than that of the sub-elemental wire. These results indicate that while high strengths and good electrical conductivities can be produced in larger size deformation processed Cu-Nb composites by a process of bundling, extrusion and cold drawing of sub-elemental wires, there appears to be a limit to the amount of subsequent cold drawing feasible before the benefit in properties ceases.     

Enhancement of strength and electrical conductivity for a dilute Al-Sc-Zr alloy via heat treatments and cold drawing

Developing heat-resistant conductors with high strength and high electrical conductivity is a key issue in the electrical conductor industries, as the ever-increasing power transmission poses higher requirement on the thermal stability of electrical conductor wires. Dilute Al-Sc-Zr alloys are considered as promising candidates due to the excellent heat resistance and high electrical conductivity, but the low strength always limits their application on electrical wires. Yet, few efforts on process design have been made in dilute Al-Sc-Zr alloys to enhance the strength. Here, various kinds of processing paths via combination of cold drawing, ageing and/or annealing were conducted to improve the strength and electrical conductivity of a dilute Al-Sc-Zr alloy. Results show that enhanced strength and electrical conductivity were obtained after cold drawing + ageing or pre-ageing + cold drawing + annealing treatments processes. Optimal properties (194 MPa in ultimate tensile strength and 61% IACS in electrical conductivity) were obtained through cold drawing followed by ageing. Microstructure evolution which affects strength and electrical conductivity was systematically investigated using TEM and 3DAP. The enhanced strength was mainly attributed to the suitable interactions between strain strengthening and precipitation strengthening. The enhancement in electrical conductivity was caused by precipitation of solute atoms and recovery of defects. These results provide foundations for the processing design of Al-Sc-Zr conducting wires with good properties and push forward their potential application in heat resistant conductor industries.