Cross Accumulative Roll Bonding Research Articles

Effects of annealing temperature and layer thickness on hardening behavior in cross accumulative roll bonded Cu/Fe nanolamellar composite

Bulk Cu/Fe nanolamellar composites with different layer thickness were fabricated by cross accumulative roll bonding (CARB) technique. Here, annealing induced hardening and strengthening behaviors were observed in these composites as annealing temperature rises up to 400 °C. Especially, the increasing rate of strength and hardness are more remarkable in those with thinner layers. Then, mechanical properties gradually degrade after annealing at higher temperatures due to the destruction of layer structure. Detailed microstructural characterizations demonstrate that miraculous abnormal hardening of Cu/Fe nanolamellar composites induced by annealing is attributed not only to the density reduction of mobile dislocation inside heterogenic layers but also to the relaxation of non-equilibrium interphase boundaries. Furthermore, this phenomenon is closely correlated with the individual layer thickness, which is revealed by the diffusion effect of excess defects in the interfacial transition zones.

Comparative Study of the Planar Uniformity of the Mechanical Properties of the AA1050 Strips Processed by Conventional and Cross Accumulative Roll-Bonding Techniques

In this research, a modified method of the conventional accumulative roll-bonding (ARB) process, named cross accumulative roll-bonding (CARB), was applied on an AA1050 strip for up to 13 cycles. The planar uniformity of the mechanical properties in the products of ARB and CARB processes has not been investigated yet. This article aims to compare the planar inhomogeneity of the tensile properties in different directions of the rolling plane of the ARB- and CARB-processed specimens. For this purpose, uniaxial tensile tests were performed in the rolling, transverse, and diagonal directions of the products. Furthermore, Vickers microhardness was used to investigate the hardness distribution throughout the thickness of specimens. The results revealed that the CARB process exhibited higher tensile strength, elongation, and hardness with more homogeneous distribution of the hardness and particularly better planar uniformity of the tensile properties compared with the conventional ARB process.

Microstructure and mechanical properties of Mg-5Li-1Al sheets processed by cross accumulative roll bonding

Mg-5Li-1Al alloy was processed by cross accumulative roll bonding (CARB). The processed Mg-5Li-1Al sheet possesses ultra-fine grains, and its strength increases both in the rolling direction (RD) and transverse direction (TD) with the elongation remaining 16˜18%. The proper CARB processing is helpful to improve the isotropy of mechanical properties of Mg-5Li-1Al sheet. At the same time, the CARB process has a beneficial effect on improving the plasticity of Mg-5Li-1Al sheet. With the change of the direction between the CARB passes, the basal texture of Mg-5Li-1Al sheet is weakened, and the non-basal texture is strengthened. Both prismatic slip and pyramidal slip are initiated. The dominant deformation mechanism changes from twin deformation to slip deformation, and finally shear deformation. The grain refinement mechanism changes from twin dynamic recrystallization to continuous dynamic recrystallization, and finally rotational dynamic recrystallization.

Aluminum-matrix composites reinforced with E-glass fibers by cross accumulative roll bonding process

In this research, the structure and mechanical properties of 1050 aluminum strips reinforced with E-glass fibers, processed by the cross accumulative roll bonding (CARB) process, were investigated from microscopic, hardness, tensile and peeling viewpoints. The results indicated that the incorporation of the glass fibers in the Al matrix increases strength and micro-hardness but decreases elongation. In addition, it was realized that some of these fibers are broken and changed to short fibers during the CARB process. The presence of the glass fibers strongly also reduces the bond efficiency of the Al strips, typically from 50% to 5%. To compensate this deleterious effect, it was found that at least 25% should be increased to the normal thickness reduction used in CRAB.

Fine Texture Enhancement of Al-Mg-SC alloy by Using Cross Accumulative Roll Bonding Technique

Aluminum alloys were as a rule used to fabricate in a few car and aviation parts. Al-Mg-Sc combination sheets were prepared a couple of cycles of Cross accumulative roll bonding (CARB) & similarly of accumulative roll bonding (ARB). In these two procedures Micro-structural advance have been occurring. It was clearly observed microstructure depicted by checking electron microscopy (SEM). In the midst of these both the system, Al-Mg-Sc alloys was adequately made with no disfigurement. In the midst of CARB process, Reinforcement (Mg, SC) particles reliably scattered inside Al system differentiated and similarly examined Al-Mg-Sc alloys in ARB process. In these two procedures, to incorporating of minor Sc in Al-Mg was extended hardness and besides it credited to the fine surface development. TEM imaging demonstrates development of fine hastens shaped inside grid in CARB contrast and ARB amid heat treatment. The Al-Mg-Sc alloy hardness was evaluated with using a Vickers hardness analyzer.

Accumulative Roll Bonding at Room Temperature of a Bi‐Metallic AA5754/AA6061 Composite: Impact of Strain Path on Microstructure, Texture, and Mechanical Properties

Accumulative roll bonding (ARB) is performed at room temperature on an aluminum composite up to five rolling cycles, using two different paths: the conventional one (ARB) and the cross ARB (CARB) one consisting of a 90° rotation of the rolling direction before each rolling pass. The microstructure is refined faster by CARB than by ARB occasioning higher yield strength of the elaborated samples. Besides, CARB has the ability to delay the loss of stratification of the composite. The resulting textures are different: while ARB promotes typical rolling components (Brass {011}<211>, Goss {110}<001>, Dillamore {4 4 11}<11 11 8>), S {123}<634>), CARB promotes the ND‐rotated Brass {011}<755> instead of Brass together with the S and Dillamore components. A Visco‐Plastic Self‐Consistent (VPSC) simulation highlights that the ND‐rotated Brass had Brass and S components for origin. The ND‐rotated Brass presence in the texture promotes a better mechanical isotropy of the composite sheet.

Microstructure and Microtexture Evolution of Invar Alloy after Cross Accumulative Roll Bonding (CARB) Compared to ARB

The microstructure and microtexture evolution of a Fe-36%Ni alloy processed by cross accumulative roll-bonding was investigated using Electron BackScatter Diffraction. Deformation led to the development of elongated ultrafine grains parallel to the rolling direction that subsequently became more equiaxed. The grains were more effectivelly refined after CARB than after ARB processing. The grain aspect ratio (l/L) decreased (which means a trend towards elongated sub-grain structure) after 2 and 3 CARB processing cycles and then increased (which means a trend towards equiaxed subgrain structure) from 4 to 5 cycles. The fraction of HAGB, CSL boundaries and the estimated deformed volume fraction gradually increased with increasing number of CARB cycles. Copper-type texture was observed after CARB odd cycles (RD//RD), while after even cycles (RD//TD) a new texture component named H ({012}<221>) was observed.

Effect of strain path on microstructure, deformation texture and mechanical properties of nano/ultrafine grained AA1050 processed by accumulative roll bonding (ARB)

Commercial pure Al sheets were severe plastically deformed at room temperature by accumulative roll bonding (ARB) and cross accumulative roll bonding (CARB). Change in strain path was imposed during CARB by rotating the sheets with 90° around the normal direction axis between each cycle. Microstructural evolution of processed sheets was studied by electron back scattered diffraction (EBSD) analysis and revealed that nano/ultrafine grains (NG/UFG) with the average grain size of 380nm and 155nm were formed by both processing routes after eight cycles, respectively. The fraction of high angle grain boundaries and mean misorientation angle of the boundaries in the CARB were 49% and 40.20°, respectively, in comparison to that of ARB sample (41% and 37.37°). Deformation texture evolution demonstrated that the change in strain path leads to the formation of strong orientation along the β-fiber. The major texture components for ARB specimens were Brass {011}<211> and S {123}<634> while those for CARB were Brass {011}<211> and Goss {011}<100>. The CARB processed specimen exhibited the tensile strength, microhardness and elongation of about 230MPa, 92HV and 13% compared with ARB sample (180MPa, 80HV and 10.5%) after eight cycles. Scanning electron microscopy (SEM) observations of tensile fracture surface of specimens revealed ductile type fracture.

High strength and thermal stability of bulk Cu/Ta nanolamellar multilayers fabricated by cross accumulative roll bonding

Bulk Cu/Ta nanolamellar multilayers with an individual layer thickness from several micrometers down to 50 nm were successfully fabricated via a combination of cross accumulative roll bonding (CARB) and an intermediate annealing step. This fabrication technique allowed to effectively suppress the formation of plastic instabilities and edge cracks during the repeated rolling process. A transition of the layered morphology from non-planar interfaces at the submicron level to nearly planar interfaces at the nano-scale was observed with decreasing layer thickness. High resolution transmission electron microscopy, selected area electron diffraction and X-ray diffraction were performed, and the results indicate that the Cu/Ta nanolamellar multilayers with a layer thickness of 50 nm show a {100}Ta[110]∥{110}Cu[111] rolling texture relationship. Tensile tests revealed that the ultimate tensile strength of the composite was up to 950 MPa, which is approximately 5 times higher than that of the initial pure Cu and Ta. The hardness of the prepared multilayer maintained unchanged even after an annealing at 500 °C for 1 h. These unique properties are attributed to an atomically flat bimetal interface and the low amount of homophase grain boundaries resulted from the CARB process.

An alternative method for manufacturing Al/B4C/SiC hybrid composite strips by cross accumulative roll bonding (CARB) process

For the first time, the cross accumulative roll bonding (CARB) process was used as an effective alternative method for manufacturing Al/B4C/SiC hybrid composite strips and compared with the accumulative roll bonding (ARB) processed hybrid composite. The XRD results showed that nanostructured Al/B4C/SiC hybrid composites have successfully been fabricated by using CARB process without any additional phase. During CARB, the ceramic reinforcement particles (B4C and SiC) were more uniformly dispersed within the matrix compared with ARB process, due to changes in strain path. In addition, the tensile strength, elongation, and microhardness of CARB composites were measured to be higher than those in the ARB product. Finally, scanning electron microscopy (SEM) observations of fractured surfaces showed that fracture mode both hybrid composites was shear ductile rupture, dimples, and shear zones.

Microstructure, mechanical properties and texture of an AA6061/AA5754 composite fabricated by cross accumulative roll bonding

AA6061 alloy is a widely used material in the automotive and aerospace industries, but is prone to hot cracking, which limits its weldability. To prevent this phenomenon, the AA6061/AA5754 composite was formed using a severe plastic deformation technique, Cross Accumulative Roll Bonding (CARB), at an elevated temperature (350°C) to ensure good bonding between layers. This technique was efficient to maintain a small grain size, even under the process temperature conditions, and consequently, preserve good mechanical properties.The composite had better mechanical properties than the initial aluminium alloys. Microstructure and texture remained stable after two cycles and yield stress tended towards an equal value in the rolling and the transverse directions. After two cycles, the main component was the {001}〈110〉 rotated Cube, which was maintained for up to 10 cycles. Diffusion was more effective as the strain increased. Finally, a tungsten inert gas (TIG) welding process was performed on the composite and confirmed resistance to hot cracking.

A comparative study on metal–matrix composites fabricated by conventional and cross accumulative roll-bonding processes

This paper focuses on some structural and mechanical characteristics of Al–Al2O3 composites produced by conventional accumulative roll-bonding (ARB) and cross accumulative roll-bonding (CARB). The obtained structures were studied by transmission electron microscopy, X-ray diffraction, and optical microscopy; typically, the reinforcement distribution on different orthogonal planes was quantitatively compared. Also, the composite samples were mechanically characterized by hardness, uniaxial tensile, and fractographic experiments. The results showed that the CARB process, compared with ARB, gives rise to somewhat more effective grain refinement. Concerning the particles dispersion, the lateral rolling planes of the CARB samples, contrary to those of the ARB composites, present a similar feature. It was also found that the hardness, yield stress, tensile strength, and elongation of the CRAB specimens are higher than those of the ARB composites.

Comparison between ARB and CARB processes on an AA5754/AA6061 composite

The present work aims to compare two processes: Accumulative Roll Bonding and Cross Accumulative Roll Bonding (CARB). Both processes consist in the repetition of rolling but the second technique adds a 90° rotation of the sheet around its normal direction between each rolling. Microstructure, mechanical properties and texture were compared for both processes on an AA5754/AA6061 composite. As a result a thinner and less elongated microstructure was obtained in the CARB process leading to an isotropy and an improvement of the mechanical properties. Besides, the texture was characterized by the rotated Cube component for both processes but for CARB it is of less strength.

Processing of ultrafine-grained aluminum by cross accumulative roll-bonding

In this paper, the structural and mechanical characteristics of aluminum strips subjected to two severe plastic deformation processes, namely accumulative roll bonding (ARB) and cross accumulative roll bonding (CARB), are compared. Transmission electron microscopy studies on the strips showed that ultrafine grains are formed by both of the processing routes to eight passes. However, the structure of the CARB-processed specimen was less elongated than that of the ARB-processed specimens; that is, the aspect ratio of grains in the CARB case was less than that in the ARB specimens. Tensile tests indicated that the tensile strength is increased with the number of rolling passes, and the strength of the CARB specimens is higher than that of the ARB specimens.

Application of compocasting and cross accumulative roll bonding processes for manufacturing high-strength, highly uniform and ultra-fine structured Al/SiCp nanocomposite

In order to achieve a refine microstructure along with improvement of mechanical properties of cast Al/2vol% SiCp nanocomposite, cross accumulative roll bonding (CARB) process was employed. Optical and electron microscopies, the Archimedes method, and tensile test were used to evaluate microstructural evolution and mechanical properties of the nanocomposites during CARB cycles. Results showed that the microstructure of the nanocomposite after eight cycles of CARB had homogenous distribution of SiC nanoparticles in aluminum matrix without any remarkable porosity. The results of transmission electron microscopy showed that ultra-fine structured Al/SiCp nanocomposite was successfully achieved by employing eight cycles of CARB technique. Also, the tensile strength and the elongation of the nanocomposite increased as the number of CARB cycles increased. After eight CARB cycles, ultimate tensile strength and the elongation values reached 354MPa and 6.9%, which were 3.22 and 3.28 times greater than those of the as-cast nanocomposites, respectively. Strengthening mechanisms were explained by strain hardening, grain refinement, reinforcing role of nanoparticles, uniformity of reinforcement and porosity.

Cross accumulative roll bonding—A novel mechanical technique for significant improvement of stir-cast Al/Al2O3 nanocomposite properties

Lightweight metal-matrix nanocomposites (MMNCs—metal matrix with nanosized ceramic particles) can be of significance for automobile, aerospace, and numerous other applications. There are some problems in obtaining suitable mechanical properties of MMNCs, including weak bonding between reinforcement and matrix, non-uniformity of reinforcement nanoparticles and high porosity content. In this study, aluminum/alumina nanocomposite was fabricated by stircasting method. Subsequently, cross accumulative roll bonding (CARB) process was used as an effective method for refinement of microstructure and improvement of mechanical properties. The microstructural evolution and the mechanical properties of the nanocomposites during various CARB cycles were examined by the Archimedes method, X-ray defractometer, scanning electron microscopy and tensile testing. The results showed that the microstructure of the nanocomposite after eight cycles of CARB had an excellent distribution of alumina nanoparticles in aluminum matrix without any remarkable porosity. The X-ray diffraction results showed that the crystallite size of the nanocomposite was 71nm by employing eight cycles of CARB technique. Mechanical experiment also indicated that the ultimate tensile strength and the elongation of the nanocomposite increased as the number of CARB cycles increased. After eight CARB cycles, ultimate tensile strength and the elongation values reached 344MPa and 6.4%, which were 3.13 and 3.05 times greater than those of as-cast nanocomposites, respectively.

Microstructural characterization of high strength and high conductivity nanocomposite wires

Bulk Cu/Ag multilayered composites with controlled individual layer thickness (h) varying from several hundred micrometers down to 20 nm were fabricated via cross accumulative roll bonding (CARB). The well-defined, continuous Cu/Ag multilayer structure with flat, planar, and sharp interfaces was found to remain stable when the layer thickness was reduced from several hundred micrometers down to 20 nm. A preferential interface character of {110}Cu[111]//{110}Ag[111] was formed when the layer thickness was reduced to 20 nm. Specifically, high strength, high electrical conductivity and excellent thermal stability were obtained simultaneously in bulk Cu/Ag nanolayered composite with h = 20 nm. Ultimate tensile strength of 938.1 MPa was achieved, corresponding to 2.9 times higher than the rule-of-mixtures estimate based on the strength of the heavily deformed Cu and Ag samples with 95% rolling reduction. Furthermore, a high electrical conductivity higher than that of pure copper was obtained, while high hardness (3.74 GPa) was maintained up to an annealing temperature of 500 °C. Nevertheless, degradation of the mechanical hardness and nanolayered structure occurred once the temperature exceeded 500 °C. Two major mechanisms are responsible for driving the onset of the thermal instability in this CARB-processed Cu/Ag nanolayered composites, namely triple junction motion and Rayleigh instability mechanisms.