累积叠轧焊制备Al／AZ31多层复合材料及其强度

采用累积叠轧焊法制备了Al/AZ31多层复合材料,并通过扫描电镜、X射线能谱仪和显微硬度计对所制备的Al/AZ31多层复合材料进行了横截面形貌观察、能谱分析以及显微硬度测试.结果表明,经过三道次的累积叠轧焊之后可制备Al/AZ31多层复合材料.能谱分析表明,在Al层和AZ31层的界面处产生了扩散层.随着轧制道次的增加扩散层的厚度逐渐增加.显微硬度测试表明,随着轧制道次的增加,Al/AZ31多层复合材料的层组元的强度也随之增加,但Al层的强度较AZ31增加得快,并且形成的界面扩散层具有一定的硬度梯度.     

Texture Evolution of Nanostructured Aluminum/Copper Composite Produced by the Accumulative Roll Bonding and Folding Process

In this study, the accumulative roll bonding and folding (ARBF) process was used for manufacturing nanostructured aluminum/copper multilayered composites. Textural evolution during the ARBF process of composites was evaluated using X-ray diffraction. Microstructural observation of some samples was evaluated by scanning electron microscopy and transmission electron microscopy. The ARBF process induced formation of a strong preferred orientation along the β-fiber and also to the pronounced copper texture component. In the aluminum side, occurrence of dynamic recovery reduced the intensity of the β-fiber rolling texture due to change in dislocation structure and decrease in the degree of strain hardening. On the other hand, occurrence of discontinuous dynamic recrystallization at the third and fourth ARBF cycles led to decreasing the intensity of fibers and texture components in the copper side. The average grain sizes of the final sample for the copper and aluminum sides were ~50 and ~200 nm, respectively.     

High Strength and Thermal Stability of Multilayered Cu/Al Composites Fabricated Through Accumulative Roll Bonding and Cryorolling

Multilayered Cu/Al composites with high strength and thermal stability were successfully fabricated by combining accumulative roll bonding (ARB) and cryorolling. The microstructure, tensile properties, and thermal stability of the multilayered Cu/Al composites subjected to cold rolling and cryorolling were analysed. Subsequent cryorolling can be used to modify interfacial flatness and local necking, induce the formation of high-density stacking faults in the Cu matrix, and enhance interfacial bonding strength, which improves the mechanical properties of ARB composites. The initial lamellar structure is gradually transformed into serious mixing with an increase in annealing temperature, accompanied by the formation of excessive Cu–Al intermetallic compounds (IMCs). Cryorolled samples exhibited higher thermal stability than cold-rolled samples. At low annealing temperature, high-density stacking faults induced by cryorolling facilitated the transition from low-angle grain boundaries to high-angle grain boundaries, which led to the formation of ultra-fine grains. For the samples annealed at high temperatures, cryorolling led to the effective inhibition of Cu–Al IMC formation and growth due to the genetic effect of less heat input.

Graphical Abstract

     

Corrosion Behavior of Ultra Fine Grain Copper Produced by Accumulative Roll Bonding Process

In this study the effect of microstructure changes on the corrosion behavior of pure tough pitch copper in 3.5 % NaCl solution with pH = 5.5 at ambient temperature was studied. Accumulative roll bonding process as severe plastic deformation was applied up to 8 cycles to produce the ultrafine grain copper. For corrosion resistance investigations, the polarization and electrochemical impedance spectroscopy was used. Corrosion morphologies analyzed by FE-SEM microscopy after polarization and immersion tests. Results show the minimum corrosion resistance for cycle 2 and maximum corrosion resistance for cycle 8. Corrosion rate of copper decreased after it was rolled for forth time. The corrosion degradation in cycle 8 was uniform and it was intergranular for sample of cycle 2 and unrolled counterpart. The higher corrosion rate in cycle 2 was attributed to unstable microstructure and the uniform corrosion of cycle 8 was due to ultra fine grain formation.     

Abnormal Ductility Increase of Commercial Purity Al During Accumulative Roll Bonding

In this paper, sheets of commercial purity Al were fabricated by the accumulative roll-bonding (ARB) method up to six cycles. To increase the shear deformation, no lubricant was used during the ARB processing and the samples were carried out for ARB processing without any preheat treatment. One interesting finding is that the ductility and strength both increased during the first several cycles of ARB processing. It is proposed that the initial rolling texture might play an important part in the subsequent ARB processing since the original Al sheets for ARB processing have not been subjected to any annealing. The microstructures of the specimens after each ARB cycle were investigated by transmission electron microscopy and correlated with the mechanical properties.     

Microstructure and Mechanical Properties of AA5005/AA6061 Laminated Composite Processed by Accumulative Roll Bonding

The AA5005/AA6061 laminated composite has been fabricated by the accumulative roll bonding (ARB) using commercial AA5005 and AA6061. In the ARB process, one piece of AA5005 sheet and one piece of AA6061 sheet were stacked together and rolled with a 50 pct reduction without any lubrication. The materials were heated at 473 K (200 °C) for 10 minutes before each rolling process and were deformed up to four cycles to accumulate an equivalent strain of 3.2 and form an AA5005/AA6061 laminated composite. Mechanical properties and microstructure of the laminated composites were tested. The hardness and tensile strength increased, and the grain size reduced with the number of ARB cycles. Ultrafine grains elongated along the rolling direction were developed during the ARB process. The thicknesses of the grains of both the AA5005 and AA6061 layers were less than 200 nm after the fourth cycle. The uniform elongation decreased drastically after the first cycle ARB and stayed almost unchanged after further ARB process. The hardness of the AA5005 layer was slightly lower than that of the AA6061 layer. The microstructures from optical microscope and transmission microscope showed that in the AA6061 layer large precipitates in the micron scale and small particles less than 100 nm were present, whereas in the AA5005 layer there were large scale precipitates, but no small-sized particles.     

An Investigation of Interface Bonding of Bimetallic Foils by Combined Accumulative Roll Bonding and Asymmetric Rolling Techniques

The bond strength in bimetallic materials is an important material characteristic. In this study, 0.1-mm thick bimetallic foils (AA1050/AA6061) were produced using one pass of accumulative roll bonding followed by three passes of asymmetric rolling (AR). The AR passes were carried out at roll speed ratios of 1.0, 1.1, 1.2, 1.3, and 1.4 separately. Finite element simulation was used to model the deformation of the bimetallic foils for the various experimental conditions. Particular attention was focused on the bonding of the interface between AA1050 and AA6061 layers in the simulation. The optimization of the roll speed ratio was obtained for improvement of the bond strength of the interface of AA1050/AA6061 bimetallic foils during AR process. In the simulation, the mean equivalent strain at the interface zone between the AA1050 and AA6061 layers was seen to reach a peak value at a roll speed ratio of about 1.2 to 1.3, which also corresponded to a high quality bond at the interface as observed experimentally.     

Reaction zone microstructure in a Ti3Al + Nb/SiC composite

A composite of Ti-25Al-13Nb (atomic percent) matrix with a continuous SiC fiber (SCS-6) reinforcement was fabricated by hot pressing powder cloths and mats of fiber. The fiber/matrix reaction zone was studied using scanning electron microscopy (SEM) and transmission electron microscopy/analytical electron microscopy (TEM/AEM) techniques. The extent of reaction was determined, phases were identified, and solute partitioning among the phases was determined. It was found that the matrix had reacted only with a portion of the carbon-rich outer layer of the SCS-6 fiber. The reaction zone contained two concentric zones which are distinguished by the presence of different carbide phases. Both zones contained a hexagonal Si-bearing phase, and one of the zones also contained some fine scattered porosity. The results are discussed with reference to available phase equilibria data. This paper is based on a presentation made in the symposium “Interfaces and Surfaces of Titanium Materials” presented at the 1988 TMS/AIME fall meeting in Chicago, IL, September 25–29, 1988, under the auspices of the TMS Titanium Committee.     

Effect of Particles Content on Microstructure,Mechanical Properties,and Electrochemical Behavior of Aluminum-Based Hybrid Composite Processed by Accumulative Roll Bonding Process

Metallurgical and Materials Transactions A - Effect of B4C/SiC particles content on the microstructure, deformation, and electrochemical behavior of aluminum-based hybrid composite processed by...     

铝合金/纳米碳管/钛复合层激光合金化组织

使用真空镀的方法在铝合金表面形成CNTs／Ti/Al/…多层复合，经激光合金化形成复合涂层。利用X射线衍射和扫描电镜对复合层的相构成及微观组织进行了分析。结果表明：铝合金表面复合层在激光合金化后存在着TiC颗粒和CNTs，TiC的含量随着激光功率的增加而增加；CNTs仍保留其原有的管状结构，且在复合层中相互缠绕呈网状均匀弥散分布；反应原位合成的TiC颗粒尺寸均匀细小，附着于CNTs上．从而改善了CNTs与基体之间的结合性能。     

Achieve High Interfacial Bonding Strength of Ti/Al Laminated Composite at Room Temperature via Electropulsing-Assisted Ultrasonic Additive Manufacturing

Metallurgical and Materials Transactions A - In this paper, electropulsing (EP) was employed to assist ultrasonic additive manufacturing (UAM) of Ti/Al laminated metal composites (LMCs). By...     

Fabrication of High-Strength Al/SiC<Subscript><Emphasis Type="Italic">p</Emphasis></Subscript> Nanocomposite Sheets by Accumulative Roll Bonding

Accumulative roll bonding (ARB) was successfully used as a severe plastic deformation method to produce Al-SiC nanocomposite sheets. The effects of process pass and amount of SiC content on microstructure and mechanical properties of the composites are investigated. As expected, production of ultrafine grain structures by the ARB process as well as nanosize particulate reinforcements in the metal matrix composite (MMC) resulted in excellent mechanical properties. According to the results of the tensile tests, it is shown that the yield and tensile strengths of the composite sheet increased with the number of ARB cycles without saturation at the last cycles. Scanning electron microscopy (SEM) revealed that the particles had a random and uniform distribution in the matrix by the last ARB cycles, and strong mechanical bonding takes place at the interface of the particle matrix. Transmission electron microscopy (TEM) and the corresponding selected area diffraction (SAD) demonstrate ultrafine grains with large misorientation in the structure. It is also shown that by increasing the volume fraction of particles up to 3.5 vol pct, the yield and tensile strengths of the composite sheets increased more than 1.3 and 1.4 times the accumulative roll-bonded aluminum sheets, respectively.     

Properties and Mechanism of Al/St Bimetal Tube Bonding Produced by Cold Spin-Bonding (CSB) Process

Spin-bonding is a novel tube cladding method for fabrication of bilayer tubes based on flow-forming process. The bimetal Al/St tubular components have extensive application in different industries. In this paper, an Al/St bimetal tube was successfully produced at different thickness reductions from 35 to 65% and mechanical and metallurgical aspects of the joint were investigated. Peeling tests were done to investigate the strength of the bond. The results showed that an increase in the thickness reduction led to a significant increase in the bond strength. Besides, the bonding mechanism between Al as inner tube to St as an outer one resulting from spin-bonding process was investigated. The results showed that an excellent bonding of Al and St tubes could be achieved from this process. The results showed that the bonding process consisted of three stages. First, removal of surface layers resulting in contact between the virgin metals of two bond surfaces and then an unstable bond was formed that stabilized as deformation proceeded. Finally the bond strengthening occurred. The SEM micrographs of the peeled surfaces showed that removing surface films in aluminum and steel in the first stage was based on different mechanisms. Also, SEM back-scatter images of bond interface showed that no intermetallic phases were formed.     

Influence of Nb and Cu Elements on the Intermetallic Particles Morphology in Ti/Al Multilayer Composite Processed Through Hot Pressing and Rolling

Ti–Al–Nb composites were produced by solid state diffusion bonding through hot pressing and rolling followed by annealing at 700 °C for 0.5, 1, 1.5 and 2 h. The morphologies of TiAl₃ intermetallics were investigated by Scanning Electron Microscopy combined with Energy-dispersive X-ray spectroscopy. Titanium tri-aluminide (TiAl₃) particles with blocky morphology were dispersed into Aluminum matrix. In the presence of niobium and copper, TiAl₃ particles were produced in different sizes and morphologies. The presence of Nb in the composite led to the formation of irregular angular morphology, while the copper resulted in cubic morphology of the intermetallic particles. The EDS results indicated that TiAl₃, (Ti, Nb)Al₃ and (Ti, Nb, Cu)Al₃ intermetallic compounds appeared near Ti zone, Nb Zone and in the presence of Cu, respectively.     

Investigation of Bonding Behavior of AA1050/AA5083 Bimetallic Laminates by Roll Bonding Technique

In this study, 1-mm AA1050/AA5083 bimetallic laminates were produced using roll bonding (RB) process. The RB process was carried out with thickness reduction ratios of 25, 50 and 75%, separately. Finite element simulation was used to model the deformation of bimetallic laminates for various experimental conditions. Particular attention was focused on the bonding of the interface between AA1050 and AA5083 layers in the simulation. The optimization of thickness reduction ratios was obtained for improvement of the bond strength of bimetallic laminates during RB process. During the simulation, the mean equivalent strain at the interface zone between the layers was found to reach the maximum value with a high quality bond for the sample produced with 75% of thickness reduction. Moreover, the fracture surface of samples around the interface of laminates after the tensile test was studied to investigate the bonding quality by scanning electron microscopy.