Evolution of bonding interface in solid–liquid cast-rolling bonding of Cu/Al clad strip

Cu/Al clad strips are prepared using solid–liquid cast-rolling bonding (SLCRB) technique with a d160 mm × 150 mm twin-roll experimental caster. The extent of interfacial reactions, composition of the reaction products, and their micro-morphology evolution in the SLCRB process are investigated with scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). In the casting pool, initial aluminized coating is first generated on the copper strip surface, with the diffusion layer mainly consisting of α(Al)+CuAl₂ and growing at high temperatures, with the maximum thickness of 10 μm. After sequent rolling below the kiss point, the diffusion layer is broken by severe elongation, which leads to an additional crack bond process with a fresh interface of virgin base metal. The average thickness is reduced from 10 to 5 μm. The reaction products, CuAl₂, CuAl, and Cu₉Al₄, are dispersed along the rolling direction. Peeling and bending test results indicate that the fracture occurs in the aluminum substrate, and the morphology is a dimple pattern. No crack or separation is found at the bonding interface after 90°–180° bending. The presented method provides an economical way to fabricate Cu/Al clad strip directly.     

Cast-rolling force model in solid−liquid cast-rolling bonding (SLCRB) process for fabricating bimetal clad strips

Based on twin-roll casting, a cast-rolling force model was proposed to predict the rolling force in the bimetal solid?liquid cast-rolling bonding (SLCRB) process. The solid?liquid bonding zone was assumed to be below the kiss point (KP). The deformation resistance of the liquid zone was ignored. Then, the calculation model was derived. A 2D thermal?flow coupled simulation was established to provide a basis for the parameters in the model, and then the rolling forces of the Cu/Al clad strip at different rolling speeds were calculated. Meanwhile, through measurement experiments, the accuracy of the model was verified. The influence of the rolling speed, the substrate strip thickness, and the material on the rolling force was obtained. The results indicate that the rolling force decreases with the increase of the rolling speed and increases with the increase of the thickness and thermal conductivity of the substrate strip. The rolling force is closely related to the KP height. Therefore, the formulation of reasonable process parameters to control the KP height is of great significance to the stability of cast-rolling forming.     

Bonding strength of Invar/Cu clad strips fabricated by twin-roll casting process

Based on traditional twin-roll casting process, Invar/Cu clad strips were successfully fabricated by using solid Invar alloy strip and molten Cu under conditions of high temperature, high pressure and plastic deformation. A series of tests including tensile test, bending test, T-type peeling test and scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) measurements were carried out to analyze the mechanical properties of Invar/Cu clad strips and the micro-morphology of tensile fracture surfaces and bonding interfaces. The results indicate that no delamination phenomenon occurs during the compatible deformation of Invar/Cu in bending test and only one stress platform exists in the tensile stress?strain curve when the bonding strength is large. On the contrary, different mechanical properties of Invar and Cu lead to delamination phenomenon during the uniaxial tensile test, which determines that two stress platforms occur on the stress?strain curve of Invar/Cu clad strips when two elements experience necking. The average peeling strength can be increased from 13.85 to 42.31 N/mm after heat treatment at 800 °C for 1 h, and the observation of the Cu side at peeling interface shows that more Fe is adhered on the Cu side after the heat treatment. All above illustrate that heat treatment can improve the strength of the bonding interface of Invar/Cu clad strips.     

Cu/Al层厚比对波纹辊轧制Cu/Al复合板变形行为和结合性能的影响

本工作通过抗剪切强度测试、剪切断面显微观察和有限元仿真等手段对不同Cu/Al层厚比下波纹辊轧制（CRB）Cu/Al复合板的金属的变形行为和界面结合性能进行了研究。结果发现，CRB过程中界面处形成了局部强正应力和多个“搓轧区”，促进了复合板的塑性变形和界面结合。增大Cu/Al层厚比可提升Cu层的变形率和波谷界面处的正应力，有利于降低Cu/Al复合板的翘曲程度，并增强界面的整体结合性能。当层厚比从2:10增加到2:4时，界面抗剪切强度从40.39MPa上升到47.24 MPa，但界面抗剪切强度的波动逐渐增大。     

Improvement of creep rupture strength of welded joints in 9Cr Mo V Nb steels (ASTM A387-Gr.91)

Summary

This paper describes efforts to fabricate explosively welded Al/Cu clad through insertion of a Cu intermediate plate between the Al driver and Cu base plates. In explosively welded Al/Cu clad fabricated by the conventional method, generation of an excess reacted interfacial zone causes degradation of bonding properties. Application of a Cu intermediate plate is effective as a means of reducing the energy dissipated by collision. The effect of the kinetic energy lost by collision on the thickness of the reacted interfacial zone and on the bond strength are examined in experiments with stainless steel. Efforts are made to fabricate Al/Cu conductive transition joints of commercial size with a Cu intermediate plate. The bonding properties obtained are better than those obtained by the conventional method.     

铝钢复合带材异径轧制变形规律的研究

以4A60铝合金和08Al低碳钢为研究对象,利用异径轧机进行异径同速轧制,从厚度变化、硬度分布及金相组织等几个方面对薄铝复层的铝/钢轧制复合变形区的金属流动规律进行了研究分析。结果表明：铝钢轧制复合过程中铝先于钢达到稳定塑性变形,轧制复合过程中变形区可分为铝钢变形未复合区、铝钢变形复合区和钢变形区。当变形量增加到55%时,钢的硬度从约110 HV升高到210 HV,而铝层的硬度变化不大,基本保持在（40±5） HV。4A60铝和08Al钢的临界复合压下量为15%左右,当压下量超过45%时,仅发生钢的变形,而铝的厚度基本保持不变。铝层厚度与总厚度的比值（复合比）由轧前的0.054降低到轧后的0.052,说明轧制复合过程中铝的变形更大。     

Effect of clad ratio on interfacial microstructure and properties of cladding billets via direct-chill casting process

Numerical simulation and experiments were introduced to develop AA4045/AA3003 cladding billets with different clad-ratios. The temperature fields, microstructures and mechanical properties near interface were investigated in detail. The results show that cladding billets with different clad-ratios were fabricated successfully. Si and Mn elements diffused across the bonding interface and formed diffusion layer. With the increase of clad-layer thickness, the interfacial region transforms from semisolid–solid state to liquid–solid state and the diffusion layer increased from 10 to 25 μm. The hardness at interface is higher than that of AA3003 side but lower than that of the other side. The bonding strength increased with the clad-layer thickness, attributing to solution strengthening due to elements diffusion. The cladding billets were extruded into clad pipe by indirect extrusion process after homogenization. The clad pipe remained the interfacial characteristics of as-cast cladding billet and the heredity of clad-ratio during deformation was testified.     

Effect of cold-rolling and annealing on interfacial structures and properties of A500/steel bimetal strip

The effect of cold-rolling, by both a series of small passes and single-pass with different deformations as well as the subsequent annealing, on the interfacial structures and properties of A500 （AlSn8 Pb2 Si2.5 Cu0.8 Cr0. 2 ） / steel bimetal strip produced by liquid-solid roll cladding was investigated. Experimental results of the cold-rolling by a series of small passes show that the interracial bonding strength increases slightly when the total deformation is less than 7.32 % and then decreases gradually with the increase in deformation. Subsequent annealing has no effect on the interfacial structures and properties. The effect of cold-rolling by single-pass less than 33.2 % deformation on the interracial structures and properties is the same as that of multi-pass cold-rolling, whereas cold-rolling by singlepass more than 33.2% deformation followed by annealing at 350 ℃ for 2.5 h can make the interracial bonding strength increase to a great extent. Metallographic examination of the interface shows that there exist only transverse cracks within the interfacial layer and the clad strip does not split along the interface during cold-rolling if the thickness of interfacial layer is less than 4 - 5μm. The thick interfacial layer（〉5 - 6μm）, however, crumbles during cold-rolling, thus resulting in the splitting of the clad strip.     

TC4钛合金与Al6061铝合金热等静压扩散连接接头的界面特征及力学性能

对TC4钛合金和Al6061铝合金的异种金属进行了热等静压扩散连接实验,研究了TC4/Al6061连接接头的界面特征、形成机制和力学性能,并通过热力学分析解释相关实验现象。结果表明,热等静压扩散连接及后续退火处理后,两侧母材元素发生了明显的互扩散,其中Si、Mg元素在化学势驱动力作用下分别富集于扩散过渡区和Al侧界面。接头界面发生冶金反应生成TiAl₃、TiAl、Ti₃Al等金属间化合物,通过有效生成热模型计算表明TiAl₃相优先生成。硬度实验表明界面生成的Ti-Al金属间化合物具有较高的硬度。拉伸实验显示接头最大抗拉伸强度达到了144 MPa。     

电弧熔丝增材制造钛/铝复合材料的组织与性能

通过基于冷金属转移的电弧熔丝增材制造技术制备了铝/钛复合材料. 观察到钛/铝结合界面存在元素扩散,形成一定厚度的中间反应层,表明界面结合良好. 同时,通过硬度测试得到界面附近的硬度介于钛侧与铝侧之间,这主要是由于元素扩散导致界面附近生成了硬脆金属间化合物. 考虑到不同的复合比会导致不同力学性能,通过拉伸试验,研究了复合比对带缺口的钛/铝复合材料拉伸力学性能的影响规律. 结果表明,在持续拉伸载荷作用下,钛/铝复合材料的两组成层之间相互影响. 随着复合比的增加,抗拉强度和屈服强度增加,断后伸长率由于受钛铝之间冶金反应的影响较大,当钛/铝试样具有较低复合比时,其断后伸长率甚至小于单一沉积铝,随后才随着复合比的增加而增大. 另外,运用ABAQUS补充了多组复合比下钛/铝复合材料的拉伸过程,得到了复合比与屈服强度和抗拉强度的关系式.     

钛/铝/镁爆炸焊复合板波形界面及力学性能

文中提出以薄的铝合金板作为过渡层,采用爆炸焊接技术成功制备钛/铝/镁层状复合材料. 对钛/铝接合界面、铝/镁接合界面及钛/铝/镁爆炸复合板的整体力学性能进行了分析研究. OM和SEM试验结果表明,钛/铝接合界面和铝/镁接合界面均为波状接合界面,在铝/镁界面出现了局部熔化区;钛/铝接合界面为小尺寸波(λ=160 μm,h=26 μm),铝/镁接合界面为大尺寸波(λ=1 740 μm,h=406 μm);拉-剪试验表明,复合板沿着铝/镁接合界面断裂;弯曲性能测试表明,钛板一侧受拉时复合板弯曲强度和塑性均优于镁合金板一侧受拉,断裂始于铝/镁接合界面,最终从镁合金板一侧剪切断裂失效.     

Ni-P镀层对Cu/Al钎焊界面结构及性能的影响机制

为了研究Ni-P镀层对Cu/Al异种金属钎焊界面反应的影响,首次采用Zn98Al和BAl67CuSi两种钎料对含/不含Ni-P镀层的T2紫铜与3003铝合金进行了高频钎焊,获得4种不同的钎焊接头,分别对接头Cu侧界面结构、抗剪强度、断口形貌、显微硬度及弯曲形貌进行了系统研究,并与无镀层接头进行对比. 结果表明,T2表面镀覆Ni-P后,Cu/Zn98Al/Al接头中Cu基体/钎缝界面结构由扩散层+8.8 μm厚的Cu_3.2Zn_4.2Al_0.7化合物转变为1.5 μm厚的Al₃Ni化合物,而Cu/BAl67CuSi/Al接头中Cu基体/钎缝界面结构由扩散层+15 μm厚CuAl₂转变为1.8 μm厚Cu₃NiAl₆;与无镀层接头相比,镀覆Ni-P后,Cu/Zn98Al/Al接头强度略有上升,Cu/BAl67CuSi/Al接头强度略有下降,但两种接头的韧性均明显增强,力学性能试验结果与接头Cu侧界面微观组织转变规律相符. 最后建立了Cu/Al接头的界面反应模型,并阐明了Ni-P镀层对Cu/Al接头界面结构和力学性能的影响机制.     

Correlation between bonding strength and mechanical properties in Mg/Al two-ply clad sheet

The effect of interfacial bonding strength has been investigated in relation to mechanical properties of roll-bonded two-ply Mg/Al clad sheets in this study. Two types of thin reaction layers (Mg₁₇Al₁₂ and Mg₂Al₃ phase layers) were observed to form along the Mg/Al interface and their thickness was found to increase with annealing time. The maximum average bonding strength was achieved after annealing Mg/Al clad sheet for 10 min at 300 °C. The fracture strain of Mg alloy in this annealed clad sheet was found to increase up to 22.5% compared to 17.8% of monolithic AZ31 Mg alloy. In addition, the formability of clad Mg alloy was also found much higher compared to those of monolithic Mg alloy. This ductility enhancement of clad Mg alloy appears due to more prolonged homogeneous deformation, caused by delayed localized necking.     

Si对Cu/Al冷轧复合界面组织与力学性能的影响

通过铝层Si合金化手段,制备了Cu/Al-Si合金冷轧复合带。利用金相显微镜、扫描电镜、万能材料试验机等仪器,研究了不同Si含量对Cu/Al-Si合金冷轧复合带界面扩散层厚度、界面结合强度、界面和基体处的显微硬度以及再结晶组织等的影响规律。结果表明,铝层中一定量的硅合金化可以起到阻碍铜铝原子互扩散、抑制铜铝金属间化合物的生长、提高铝侧基体显微硬度以及细化晶粒等作用,但是在高温、长时间热处理条件下,硅会降低界面的结合强度。     

A356浇覆温度对铝/钢复合板界面组织及力学性能的影响

先采用热浸镀铝?锌工艺对Q235钢板进行表面镀层处理,后将液态的A356铝合金定量浇覆于经预热的钢板表面,通过液固铸轧成功制备铝/钢复合板。运用光学显微镜(OM)、SEM观察界面结合与组织形貌,结合EDS、XRD分析界面物相成分,并测试微观硬度、室温拉伸和剪切强度。结果表明:随着浇覆温度的提高,复合板界面间隙消失,整体趋势上扩散层厚度逐渐增加。当浇覆温度为710℃及以上时,界面处会形成Fe3Al、FeAl、FeAl2、Fe2Al5和FeAl3相。在同一浇覆温度下,硬度整体趋势为在Q235和A356基体中保持稳定,而在从Q235侧距界面中心100μm至A356侧距界面中心100μm的范围内连续下降。抗拉强度和剪切强度都表现出先增加后减小的趋势,浇覆温度为710℃时,复合板的成形质量最佳,抗拉强度和剪切强度都为最大,分别为336.4 MPa和137.6 MPa。     

Coupled analysis of temperature and flow during twin-roll casting of magnesium alloy strip

The distribution of temperature and flow fields in cast-rolling zone was obtained through the direct coupled solution of finite element method. Two vortexes appeared in the cast-rolling zone during twin-roll casting. The flow velocity along thickness of the magnesium alloy strip was heterogeneous, which resulted in the microstructure with the flow trace inclined to the cast-rolling direction. The temperature difference between the strip surface and at the center was about 150 °C at the inlet and it declined to about 25 °C at the exit. The increase of the casting temperature caused the raise of the strip temperature at the exit. The calculated temperature was consistent with the measured temperature.     

焊丝成分对铝/铜激光熔钎焊接头组织和性能的影响

通过添加Zn-Al焊丝成功实现了2A16铝合金/T2铜异种材料的激光熔钎焊连接,并采用扫描电子显微镜和能谱仪对接头的微观组织进行表征,同时,研究了Zn-2％Al,Zn-5％Al和Zn-10％Al?3种焊丝对接头成形、微观组织以及力学性能的影响.结果表明,铝/铜激光熔钎焊接头主要由CuZn相,Al2Cu相,Al4Cu9相...     

Evaluation of intermediate phases formed on the bonding interface of hot pressed Cu/Al clad materials

The aim of the present study is to identify the properties of intermediate phases formed on the bonding interface of hot pressed Cu/Al clad materials by transmission electron microscopy and nano-indentation analyses. Cu/Al clad materials were fabricated by hot pressing under 200 MPa at 250 °C for 1 h and then heat treated at 400 °C for 1 h. Nano-indentation measurement was conducted to evaluate the nanohardness and modulus of the intermediate phases formed between the Cu/Al interfaces. A 3-tier diffusion layer was observed at the Cu/Al interfaces. Knoop microhardness values at the bonding interface were 7 to 11 times that of the Cu and Al matrix metals. The intermediate phases formed at the bonding interface were Al4Cu9, AlCu, and Al₂Cu. A mapping analysis confirmed that the Al and Cu particles moved via mutual diffusion toward the intermediate phases formed at the bonding interface. The nanohardness values of η₂-AlCu and γ1-Al₄Cu₉ were 4 to 7 times that of the Cu and Al matrix metals. Nanohardness and Knoop microhardness measurement curves exhibited similar tendencies. The rigidity values of the respective intermediate phases can be arranged in descending order as follows: γ₁-Al₄Cu₉ > η₂-AlCu > θ-Al₂Cu.     

压下率对冷轧铝/钢(4A60/08Al)复合带材组织性能的影响

结合金相组织观察、显微硬度测量及室温拉伸实验, 对压下率分别为30%、40%、50%及60%时的4A60/08Al冷轧复合带的组织与力学性能进行了研究。采用模拟钎焊后拉剪实验对复合带的界面结合强度进行了评价。结果表明: 随着压下率的增加, 复合带钢层的硬度和屈服强度明显增加, 而铝层的硬度变化不大; 压下率从30%增加到50%时, 界面平均抗剪强度从52 MPa增加到65 MPa, 拉剪断裂位置也从铝钢界面断裂过渡到铝层断裂, 因此把压下率50%定义为4A60/08Al冷轧复合带的稳定压下率; 另外, 当压下率超过50%时, 复合带材的钢层在520℃×24 h退火后的组织基本为等轴的再结晶组织, 综合力学性能良好。     

爆炸焊接TA1/Al复合管的界面及性能研究

采用爆炸焊接工艺对TA1管材及Al管进行了爆炸复合。利用SEM、XRD对复合管结合区形貌及相组成进行了研究;测试了复合管的结合强度及过渡区的显微硬度,并进行了轴向压缩、径向压扁试验。结果表明:直线状及波状界面同时存在于过渡区;过渡区域出现了明显的元素扩散现象;界面结合强度不低于纯铝剪切强度;轴向压缩、径向压扁后的复合管试样均未出现分层,说明TA1/Al复合管坯界面结合性能优异,可以承受大的塑性变形。