In this paper, an ultra-thin Cu/Al composite sheet with a thickness of 0.08 mm was obtained via the cold-rolling composite method using a four-high micro-rolling mill in the laboratory. The rolling reduction of a single pass was 65%. After the annealing of the ultra-thin Cu/Al composite sheets at temperatures ranging from 350 °C to 500 °C, the interface bonding mode of the Cu/Al composite sheets changed from mechanical bonding to metallurgical bonding, and the bonding strength was significantly improved. The microhardness value at the bonding interface of the ultra-thin Cu/Al composite sheets increases with the increase in annealing temperature. When the annealing temperature is 500 °C, the maximum microhardness value at the bonding interface reached 2.0 GPa. With the increase in annealing temperature, the tensile strength and elongation of the ultra-thin Cu/Al composite sheets decreases significantly. The peel strength of the extremely thin Cu/Al composite sheets increases at first and then decreases with the increase in annealing temperature, and reached the maximum value at an annealing temperature of 400 °C. When the annealing temperature was 400 °C, the tensile and peel properties of the ultra-thin Cu/Al composite sheet reached the best state.

High performance Cu-Al composites have widely applied in aviation, aerospace and other fields, at the same time the continuous casting as one of composite forming technologies has been also developed in recent years. Obviously, it is an effective and cheap way to numerically simulate the solidification process of short process continuous casting for manufacturing Cu-Al composites before fabricating them. To meet the need of simulation, in this work, a numerical method for theoretically describing the Cu-Al composite forming in continuous casting processes was proposed. The vertical continuous casting of copper clad aluminum bar billet and the horizontal continuous casting of copper and aluminum composite plate were performed. Based on this method, the steady state temperature fields in solidification processes in the above two kinds of casting technologies were numerically simulated by using proCAST software package. In this work the effects of the theoretical parameters on the steady state temperature fields and then on the performance of Cu-Al composites fabricated by using the above two casting technologies were carefully discussed. It is found that the experimental and simulated results are in good agreement. For the cases of the copper clad aluminum bar billet with a cross section of 100 mm×100 mm, and the copper or aluminum plate with a thickness of 20 mm and a width of 75 mm (coat thicknesses of 4~7 mm), the feasible parameters for producing high performance Cu-Al composites, for examples, are as follows: for the former the temperature of copper liquid is 1250 ℃, the temperature of aluminum liquid is 750 ℃, the length of crystallizer is 200 mm, the length of graphite mandrel tube is 290 mm, the flux of the first cooling water is 1600~2000 L/h, the flux of the second cooling water is 900~1300 L/h, the distance from the second cooling water to the exit of crystallizer is 30 mm, and the withdrawing speed is 60~80 mm/min. For the latter the temperature of copper melt was 1250 ℃, the temperatures of aluminum melt are 760~800 ℃, the withdrawing speed is 40~80 mm/min, and the length of aluminum duct is 20 mm.

建立了Cu-Al复合材料连铸成形的数值模拟模型,确定了模型的边界条件,提出了复合过程处理和结果评价方法。通过与部分实验结果对比表明,模拟结果与实验结果一致。以铜包铝棒坯立式连铸和Cu-Al复合板坯水平连铸过程为例,采用ProCAST软件对其稳态温度场进行了数值模拟分析,得到了各工艺参数对连铸过程的影响规律,给出了合理的工艺参数范围,并结合模拟的参数进行相应的实验研究。结果表明,本工作建立的连铸复合模型、确定的边界条件、提出的复合过程处理和结果评价方法合理,可有效用于连铸复合成形模拟分析。计算结果表明,制备横断面为100 mm×100 mm、Cu包覆层厚度(4~10 mm)的铜包铝棒坯可行的连铸工艺参数为：Cu液温度1250 ℃,Al液温度750 ℃,结晶器长度200 mm,芯棒管长度290 mm,一冷水流量1600~2000 L/h,二冷水流量900~1300 L/h,二冷水距结晶器出口距离30 mm,拉坯速率60~80 mm/min;制备厚度20 mm、宽度75 mm、Cu包覆层厚度(4~7 mm)的Cu-Al复合板坯可行的工艺参数为：Cu液温度1250 ℃,Al液温度760~800 ℃,拉坯速率40~80 mm/min,Al液导流管长度20 mm。

Using a new type of induction heating process, copper/aluminum composite was prepared by solid-liquid-solid method. The resistivity of binding layers of different components and the relationship between the thickness of bonding layers and the thermoelectric properties of copper/aluminum composite were investigated. The thermal conductivity was observed by xenon lamp thermal conductivity meter DXF200. The resistivity was measured by SB100A/20A four probe conductor/semiconductor resistivity tester. The results showed that the thermal conductivity of Cu/Al compound materials bonding layers is 205.6 W/(m·K) and the resistivities of Intermetallic compounds of bonding layer,Cu₉Al₄ layer, AlCu layer and CuAl₂ layer are 14.35×10^-8, 8.17×10^-8 and 11.56×10^-8 Ω·m, respectively. Moreover, with the concentration of the thickness of bonding layers, the complex thermal conductivity of copper/aluminum composite gradually decreased. When the thickness of bonding layer was in the range of 1 to 100 μm, the copper/aluminum composite produced the satisfactory thermoelectric properties.

运用新型感应加热工艺,通过固-液-固相复合法制备铜/铝复合材料。分析了不同成分结合层的电阻率及结合层厚度与铜铝复合材料热电性能间的关系。实验中用氙灯导热仪DXF200对Cu/Al复合材料结合层的导热系数进行测定,用SB100A/20A型四探针导体/半导体电阻率测试仪对Cu/Al复合材料结合层电阻率进行测定。结果表明,铜铝复合材料结合层的导热系数为205.6 W/(m·K),铜铝复合材料中间化合物Cu₉Al₄的电阻率为14.35×10^-8 Ω·m,CuAl的电阻率为11.56×10^-8 Ω·m,CuAl₂的电阻率为8.17×10^-8 Ω·m,且随着结合层厚度的增加,复合材料的等效导热系数逐渐减小,当铜铝复合材料结合层厚度保持在1～100 μm的范围时有具有较好的导电、导热性能。

Plate of Ni-clad 316H stainless steel was prepared via hot rolling process after pre-heating at 1200oC for 120 minutes, then concurrently the rolling process was interrupted after rolling for 3, 5, and 7 passes respectively, while the relevant samples are taken and water-quenched for subsequent characterization in terms of the evolution of their interface-composition and -morphology, as well as the formed oxides there. Results show that until the 3rd rolling pass, the rolling plate temperature was about 1000°C, the two metals were closely bounded with equiaxed grains of slightly distorted microstructure on both sides of the interface and the inter-diffusion of elements for the two metals was not obvious; Until the 5th rolling pass, the plate temperature was about 940°C, the grains of 316H were elongated with significant lattice distortion, whereas, obvious inter-diffusion can be found near the interface; Until the 7th rolling pass, the plate temperature was about 880°C, large number of elongated and distorted grains were observed on the 316H steel side and a fine grain structure crushed by hot rolling distributed near the interface. The elements of Ni, Fe and Cr were fully inter-diffused near the interface, but the less motionable Mo enriched at the 316H side. The grains of Ni layer coarsened obviously. The interface evolution of Ni/stainless steel composite plate during the rolling process follows the so called three-stage theory and N. Bay's theory. The physical contact stage and the physical-chemical contact stage happened between the 3rd and 5th pass. Then the rolling from 5th to 7th pass was the final physical-chemical contact phase, whilst the inter-diffusion begins, that is, the "bulk" mutual phase begins. In the high-temperature and low-oxygen environment, the Mn oxides near the interface might form during the rolling process. The oxide was crushed and squeezed toward the substrate by the rolling force, therefore distributed in chains near the interface eventually.

采用轧制终止取样法对镍-不锈钢热轧复合板轧制过程中的界面成分、界面组织以及界面处的氧化物进行了表征，研究了轧制过程中界面的结合机制并根据热力学原理解释了高温下选择性内氧化的机理。将复合板坯加热至1200℃，保温120 min后进行轧制，分别在轧制3、5、7道次后中断轧制快速水冷，随后进行取样观察。结果表明，轧制3道次时终轧温度为1000℃左右，金属之间有近距离结合，微观组织有轻微的畸变，界面两侧的板材均为等轴晶粒，元素的扩散不甚明显；轧制至5道次时终轧温度为940℃左右，316H的晶粒被拉长而发生晶格畸变，界面附近出现明显的扩散行为；轧制到7道次时终轧温度为880℃，316H层出现大量拉长的畸变晶粒，界面处主要是轧碎的细晶组织，但Ni层的晶粒粗大，界面附近Ni、Fe和Cr元素充分扩散，微弱扩散的Mo元素在316H界面富集。镍-不锈钢复合板在轧制过程中界面的演化遵循三阶段理论和N.Bay理论，3道次到5道次间处于物理接触阶段、物理化学阶段，轧制7道次时物理化学阶段结束并开始扩散，即开始进入“体”相互阶段，主要元素在此阶段完成相互扩散。在高温低氧环境的轧制条件下，界面处生成Mn的氧化物，该氧化物因轧制而破碎并向基材挤压最终在界面附近成链状分布。

Softening annealing (SA) is often required for producing medium-Mn steels (MMS) as it lowers hardness so that they can be cold rolled to reduce thickness. The influences of different SA processes on the microstructural heredity during the processing route and the final tensile properties were studied. It was found that the SA process could either intensify or weaken the influence of the Mn segregation resulting from solidification on the subsequent microstructural evolution during the process, i.e., microstructural heredity. In the case when no SA was employed, both recrystallization and rapid growth of ferrite grains preceded the reverse austenitic transformation during the intercritical annealing (IA) in the Mn-lean regions, where very coarse ferrite grains were formed. This deteriorated ductility due to the propagation of cracking along the boundary of the coarse-grained and fine-grained regions. In contrast, SA at a sufficiently high temperature could dissolve cementite, producing uniformly distributed austenite grains. They transformed to martensite during cold rolling but were reborn during IA. As a result, ultrafine austenite and ferrite grains were uniformly distributed, which improved ductility significantly. This study hints at a new approach to altering the microstructural heredity resulting from the heterogeneous Mn distribution in MMS.

The microstructural characterization and uniaxial tensile tests of Al/Cu laminated composites were taken to investigate the interface effect and fracture process of the composites. The electron microscopic graphs before and after tensile test were used to evaluate the fracture behavior. Experimental results show that the fracture surfaces of laminated composites mainly present brittle failure characteristics, accompanied with several dimples on the matrixes and a few tearing on the interface. Cracks generally initiate from the interfacial interlayer and variously propagate depending on the interfacial bonding. It is found that Cu/Al interface with enhanced bonding strength generally hinders the propagation of interlayer cracks, while the interface with weak bonding delaminates by the cracks propagation through the interfacial defects. The additional shear stress on the interface between Cu and Al layers due to their different tensile ductilities aggravates the interfacial propagation of cracks. The local plastic deformation of individual matrix layer then occurs after cracks coalesce and failure in the interface. Therefore, the strong bonding interface and matching properties between individual matrix layers are required to improve the fracture performance of Al/Cu laminated composites.

In this paper, Cu/Al laminated composite was prepared by a novel approach, corrugated + flat rolling (CFR) method, with low reduction ratio of 20% per pass, and the microstructure and mechanical properties were investigated. The results indicate that the preliminary combination of the composite can be realized by the first CFR pass and the composite with complete combination was obtained after the flattening rolling process. The corrugated bonding interface was formed without intermetallic phase, and the grain refinement (especially at the interface) occurred after the CFR process. Furthermore, the Cu/Al laminated composite with corrugated bonding interface exhibits outstanding tension-shear and tensile properties. (C) 2018 Elsevier B.V.