Accumulative Roll Bonding Cycles Research Articles

Investigation of the Microstructure and the Mechanical Properties of Cu-NiC Composite Produced by Accumulative Roll Bonding and Coating Processes

In the present study, Cu-1.8 wt.% NiC (nickel coating) composite was produced by the combination of two methods, including accumulative roll bonding (ARB) and electroplating processes. Electroplating process was done on copper strips in order to produce a nickel-particle-reinforced composite. Microstructure, texture, and the mechanical properties of the produced composite were evaluated during various cycles of ARB using optical and scanning electron microscopes, x-ray diffraction, microhardness, and tensile tests. In addition, the results were compared with Cu-Cu and also Cu-NiS (nickel sheet) samples. It was found that nickel layers were fractured from the first cycle of the process, and nickel fragments were distributed in the copper matrix as the number of cycles was increased. Variation of orientation density of α-, β-, and τ-fibers for the produced composite was examined in different cycles. Microhardness for different elements in different cycles of Cu-NiC was also evaluated. Also, the investigation of the mechanical properties showed that by proceeding the ARB process, the tensile strength of the produced Cu-NiC and Cu-Cu samples was increased. However, improvement in the mechanical properties of composite samples was more noticeable due to the reinforcing effect of nickel particles. The elongation of composite samples showed a decrease in the primary cycles, unlike Cu-Cu ones; however, it was then increased. Finally, by using scanning electron microscopy, the fracture surfaces of Cu-NiC composite were studied to disclose the fracture mechanism of the samples.

Effects of grain size and dislocation density on strain hardening behavior of ultrafine grained AA1050 processed by accumulative roll bonding

In this work, the effects of grain size and dislocation density on strain hardening behavior of ultrafine grained (UFG) AA1050 produced by 9-cycle accumulative roll bonding (ARB) process were studied. Transmission electron microscopy (TEM) micrographs indicated that UFG structure with the average grain size of 270 ± 11 nm achieved after nine cycles of ARB. The dislocation density which was measured by microhardness value increased with an increase in the number of ARB cycles. The dislocation density increased from about 7 × 1012 m−2 for annealed sample to above 2 × 1013 m−2 after nine cycles ARB. Tensile tests results revealed that with increasing the number of ARB cycles, mechanical properties of the samples improved. The Hollomon analysis was used to investigate the strain hardening behavior of AA1050 samples. The results showed that the strain hardening exponent decreased with increasing the number of ARB cycles. All ARBed samples showed high strain hardening rate in initial stage of deformation, which increased with increasing dislocation density and grain refinement.

Microstructure and mechanical properties of Al-based metal matrix composites reinforced with Al84Gd6Ni7Co3 glassy particles produced by accumulative roll bonding

Al-based metal–matrix composites reinforced with Al84Gd6Ni7Co3 glassy powders have been produced by accumulative roll bonding (ARB) for the first time. Microstructural analyses show that after nine ARB cycles, the Al84Gd6Ni7Co3 particles are homogeneously distributed in the Al matrix. The fractography of the samples indicates that an excellent metallurgical bonding is created at the Al84Gd6Ni7Co3 particles/matrix interface upon ARB cycles. Microhardness and tensile tests demonstrate that the addition of Al84Gd6Ni7Co3 glassy particles significantly improves the mechanical properties, compared to pure ARBed Al.

Microstructural evolution, mechanical properties, and strain hardening behavior of ultrafine grained commercial pure copper during the accumulative roll bonding process

In this study, the microstructural evolution, mechanical properties, and strain hardening behavior of commercial pure copper processed by the accumulative roll bonding (ARB) were investigated. Transmission electron microscopy (TEM) micrographs and atomic force microscopy (AFM) images indicated that with increasing the number of ARB cycles, the grain size of samples decreased. An Ultrafine grained (UFG) structure with an average grain size of about 200nm was achieved after four cycles of ARB. The yield and ultimate tensile strength of pure copper with the UFG microstructure was reached about 360MPa and 396MPa (about 400% and 100% higher than that of the annealed state), respectively. All ARB-processed copper samples showed lower strain hardening exponent in comparison with the annealed state. Moreover, the strain hardening rate increased with increasing ARB cycles up to 3 cycles and then decreased.

An analytical approach for necking and fracture of hard layer during accumulative roll bonding (ARB) of metallic multilayer

The critical strain for the onset of necking and fracture in the hard layer during accumulative roll bonding (ARB) of metallic multilayer was predicted using the analytical models. The critical strain for necking was determined by utilizing an instability criterion and the critical strain for fracture was predicted based on the Cockcroft and Latham criterion using the tensile fracture strain. The stress state was derived in the hard layer at the exit of the roll-gap after n ARB cycles. The models predicted that the critical strain for necking and fracture increased with increasing the thickness ratio, strength coefficient ratio and the work-hardening exponent of the hard phase while it decreased with increasing the work-hardening exponent of the soft phase. The results of the model were verified by the data extracted from the literature. In addition, ARB experiments were performed on Al/Cu and Al/Ni multilayer in order to validate the analytical model and to investigate the microstructure evolution.

Accumulative roll bonding (ARB) of the composite coated strips to fabricate multi-component Al-based metal matrix composites

A multi-component Al-based metal matrix composite was fabricated by accumulative roll bonding (ARB) of the composite coated strips. The Ni/SiC composite layer with three different thicknesses of about 25, 50 and 150µm was generated on the Cu substrate by electroplating. The coated strips were placed between two Al strips and processed by ARB up to eight cycles to fabricate the multi-component Al–Cu–Ni/SiC composites. To investigate the microstructure evolution during ARB, an Al–Cu–Ni composite was produced by the same method and using the Cu strips coated with single Ni layer. After eight ARB cycles, the microstructure of Al–Cu–25Ni/SiC composite revealed a uniform distribution of the reinforcements and good bonding at the interfaces. In Contrast, the microstructure of Al–Cu–50Ni/SiC and Al–Cu–150Ni/SiC composites was characterized by cavities and debonding at interfaces and non-uniformity of the reinforcments. The Al–Cu–25Ni/SiC composite exhibited the highest tensile strength of about 310MPa, in comparison to the annealed Al (47MPa). The lowest tensile strength was achieved in the Al–Cu–150Ni/SiC composite (about 206MPa) due to the formation of the cavities and debonding at the interfaces. Fracture surface of the composites revealed a combination of brittle and ductile fracture.

Microstructure evolution and mechanical properties of Al/Al–12%Si multilayer processed by accumulative roll bonding (ARB)

In this study, multi-layered Al/Al–12%Si composites were produced by the accumulative roll bonding (ARB) at ambient temperature using commercial pure Al 1050 and Al–12%Si alloy sheets. The microstructures of Al and Al–12%Si alloy layers were characterized by scanning electron microscopy (SEM). Vickers microhardness and tensile tests were conducted to investigate mechanical properties of the composites. It was observed that by increasing ARB cycles, thickness of individual Al and Al–12%Si alloy sheets decreased; finally, Al–12%Si layers were necked at the second cycle. After the second ARB cycle, a multi-layered Al/Al–12%Si composite with homogeneously distributed Al–12%Si layers in aluminum matrix was produced. Si phase was refined from 65.6 to 25.57µm in length and the Al grain size was reduced from 25 to 7.2μm. The formation of Al3.21Si0.47 intermetallic phase after the second cycles was confirmed by X-ray diffraction. The results showed that the tensile strength increased up to 270MPa after first cycle and dropped afterwards. Microhardness measurement indicated that hardness of individual layers increased continuously with increasing the ARB cycles.

Fabrication and characteristic of Al-based hybrid nanocomposite reinforced with WO3 and SiC by accumulative roll bonding process

In this study, Al/WO3/SiC hybrid nanocomposite was produced using Al 1050 sheets and WO3 and SiC nanoparticles through accumulative roll bonding (ARB) process. Uniaxial tensile test and hardness measurement were carried out on ARBed specimens. Scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) was used for microstructural observation. The results revealed that by increasing the number of ARB cycles, a better distribution of WO3 and SiC nanoparticles was obtained in the Al matrix. So, after the 9th cycle, the hybrid nanocomposite showed an excellent distribution of the nanoparticles with strong bonding between the nanoparticles and the aluminum matrix. It has been shown that after 9 cycles, the microstructure exhibits a uniform of ultrafine grains elongated in rolling direction with an average grain size of approximate 400 nm. Furthermore, the tensile strengths of the hybrid nanocomposite enhanced by increasing the number of ARB cycle and reached to a maximum value of 204.5Mpa at the end of 9th cycle, which was 4.02 higher than that of the starting material. Also, the microhardness results suggested that with increasing the number of cycles, hardness increased rapidly at first stages and then dwindled at the last stages.

Improving the Mechanical Properties and the Microstructure of Pb Electrowinning Anodes Using Accumulative Roll Bonding

Some lead sheets were fabricated for applying as anodes in electrowinning metal production via accumulative roll bonding (ARB) technique for the first time. Mechanical properties and the microstructure of the developed Pb anodes were evaluated using peeling tests, tensile tests, microhardness tests, shear punch tests as well as electron microscopic observations. Compared to the plain lead sheet, the mechanical properties of ARB processed Pb sheets were improved considerably, after 10 ARB cycles. It was also found that the tensile strength was raised up to 38 %, yield strength up to 103 %, shear strength up to 35 % and hardness up to 103 %, and the strain was decreased by 68 %. These superior properties were accompanied by higher stiffness and significant enhancements in the creep characteristics. Therefore, the resulting properties of the ARB developed Pb anodes guaranteed the reduction of anode failure, additional maintenance and costs in lead anode required industries.

Corrosion Behavior of Ultra-fine Grained 1050 Aluminum Alloy Fabricated by ARB Process in a Buffer Borate Solution

Accumulative roll bonding (ARB) has been used as a severe plastic deformation process for the industrial production of ultra-fine grained (UFG) and nano-crystalline sheets with excellent mechanical properties. In the present study, the effect of the ARB process on the corrosion behavior of UFG and nano-crystalline 1050 aluminum alloy in a buffer borate solution (pH 5.5) has been investigated. The result of microhardness tests revealed that microhardness values increase with an increasing number of ARB cycles. A sharp increase in microhardness is seen after three ARB cycles, whereas moderate additional increases are observed afterward for up to nine cycles. Also, the XRD results showed that the mean crystallite size decreased to about 91 nm after nine cycles. The potentiodynamic plots show that as a result of ARB, the corrosion behavior of the UFG and nano-crystalline specimens improves, compared to the annealed 1050 aluminum alloy. Moreover, electrochemical impedance spectroscopy measurements showed that the polarization resistance increases with an increasing number of ARB cycles.

Annealing Texture of Nanostructured Steel-Based Nanocomposite

In this research, the evolution of annealing texture in nanostructured steel-based nanocomposite fabricated via accumulative roll bonding (ARB) process was investigated. Textural evolution after post-annealing of ARB-processed samples was evaluated using x-ray diffraction. Average grain size of the sample before and after the post-annealing was 55 nm and 1.5 µm, and the microstructures were uniform. All the samples indicated a strong α-fiber and γ-fiber and a relatively weak ζ-fiber. Also, there were texture transitions in the α-fiber, e-fiber, γ-fiber, η-fiber, and θ-fiber. In addition, for all the samples, the intensities of the rolling textures were higher than those of the shear textures. Moreover, there was a progressive increase in the fraction of high-angle grain boundaries with the increasing strain. Finally, with increasing number of ARB cycles, the intensities of rolling and shear textures changed, and no stable texture was formed.

Annealing texture of nanostructured IF steel

In the present work, the evolution of annealing texture in nanostructured interstitial free steel fabricated via accumulative roll bonding (ARB) process was investigated. Textural evolution after post-annealing of ARB-processed samples was evaluated using X-ray diffraction. There were several texture transitions in the γ-fiber and ζ-fiber during ARB and post-annealing treatment. It was found that with increasing the number of ARB cycles, the volume fraction of the low angle grain boundary decreased and the high angle grain boundary fraction increased. Also, the shear texture was dominant after the first cycle, while for other samples, the rolling texture was dominant. The one-cycle sample clearly indicated a weak α-fiber and γ-fiber and a relatively strong ζ-fiber. In addition, during the recrystallization and before the grain growth, the intensity of α-fiber and γ-fiber decreased, the intensity of ζ-fiber increased, and the intensity of {011}〈100〉 orientation in the ε-fiber and η-fiber increased. Moreover, it was concluded that the transition from the rolling texture to the shear one was a sign of occurrence of the recrystallization (before the grain growth). Finally, with increasing the number of ARB cycles, the intensity of rolling and shear textures saturated and a stable texture formed.

On the Achievement of Nanostructured Interstitial Free Steel by Four-Layer Accumulative Roll Bonding Process at Room Temperature

In this study, the four-layer accumulative roll bonding (ARB) process at room temperature for nanostructuring the interstitial free (IF) steel was used for the first time. Hardness and tensile tests were performed and the microstructure was characterized using scanning transmission electron microscopy. It was found that the grain size decreased into the nanostructured domain after fourth cycle, reaching grain sizes of smaller than 100 nm. The stored energy was retained in the material until the continuous dynamic recrystallization led to nanostructuring of the IF steel. The dislocation density was measured by microhardness indentation size effect using the Nix–Gao model. The results indicated that an increase in the number of ARB cycles leads to increase in the dislocation density. The dislocation density increased from 2.02 × 109 cm−2 for initial sample to 9.47 × 109 cm−2 after fourth cycle. The yield strength of the IF steel after fourth cycle was 10.8 times (909 MPa) higher than that of the initial sample (84 MPa). Finally, the contribution of individual mechanisms such as the grain refinement, dislocation, and precipitation in strengthening of the IF steel were evaluated.

Fabrication of high-strength graphene nanosheets/Cu composites by accumulative roll bonding

Graphene nanosheets (GNSs) reinforced copper matrix composites have been considered as the potential copper materials with high strength and high conductivity. Here, the high-strength GNSs/Cu composites were fabricated by accumulative roll bonding (ARB). The ARBed GNSs/Cu composites manifested a good interfacial bonding and a significant grain refinement. The average spacing of high-angle boundaries along the normal direction was less than 150nm after 6 ARB cycles, which was finer than that of the ARBed Cu. In addition, there existed a nano-layer with grain sizes of 50–70nm and the high-density deformation-twins at the interface. The tensile strength of the ARBed materials enhanced with the number of cycles. After six cycles, the tensile strength of GNSs/Cu composites reached 496MPa. This strength was 275 and 33MPa higher than those of the annealed copper and the ARBed copper, respectively due to the strain hardening and grain refinement. Furthermore, the addition of GNSs into Cu matrix accelerated the grain refinement and the strength improvement.

Stress relaxation and flow behavior of ultrafine grained AA 1050

Flow behavior of ultrafine grained (UFG) AA 1050 sheets processed by Accumulative Roll-Bonding (ARB) and its viscous nature are investigated by plane strain compression test (PSC) along with stress relaxation. Occurrence of dynamic recovery is validated by TEM observations as the microstructural explanation of the flow softening at the start of deformation of the 8-cycles specimen. Significant recovery of the UFG specimens during the stress relaxation test is also disclosed. It is discussed that neither the internal stress (σi) nor the density of mobile dislocations are constant during the test. The possible effects of these two factors as well as contribution of the grain boundary sliding (GBS) on the relaxation behavior of the specimens are analyzed. It is shown that these effects can explain why the absolute value of the slope |S| of ln(-σ̇) versus ln(t) plot is smaller than unity, while based on the physical meaning of the power law model, which fits well to the experiments, the |S|<1 carries no sense. Moreover, the enhanced contribution of GBS due to grain refinement by ARB cycles seems to cause the decrease of the |S| by the number of ARB cycles.

High strength Al with uniformly distributed Al2O3 fragments fabricated by accumulative roll bonding and plasma electrolytic oxidation

Accumulative roll bonding (ARB) and plasma electrolytic oxidation (PEO) were used to fabricate Al/Al2O3 composite. A uniform distribution of Al2O3 fragments was achieved within the Al matrix after six ARB cycles. In contrast to the large fragments, small fragments contained no porosity and revealed good bonding at interfaces. The Al/Al2O3 composite exhibited improved tensile strength of about 180MPa, in comparison to the annealed Al (47MPa).

Strengthening mechanisms in nanostructured interstitial free steel deformed to high strain

In this study, the strengthening mechanisms in nanostructured IF steel deformed to high strain by four-layer accumulative roll bonding (ARB) process at room temperature in absence and presence of SiC particles were investigated. Microstructural observations were performed by scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). The results indicated that the average grain size of the pure steel, composite, and nanocomposite was 95, 73, and 55nm, respectively and the microstructures consisted of equiaxed grains. Also, with increasing the number of ARB cycles, the dislocation density of samples increased. The first cycle of ARB process had remarkable effect on the dislocation density. The value of dislocation density first rapidly increased, then dwindled, and finally saturated by further ARB cycles. The presence of SiC microparticles and nanoparticles in the IF steel matrix increased the dislocation density during the ARB process. On the other hand, dislocation density of the nanocomposite was higher than that of the composite. After first cycle, a significant increase observed in the yield strength, from 84MPa to 609, 682, and 689MPa for pure steel, composite, and nanocomposite, respectively, which was almost 7.3, 8.1, and 8.2 times greater than that of the initial sample. There was no perfect saturation in yield strength of the pure IF steel with increasing the number of ARB cycles. Finally, the contribution of individual mechanisms such as the grain refinement, dislocation, second phase, and precipitation in strengthening of the IF steel was evaluated. The contribution of grain refinement and precipitation to the improvement in yield strength was maximum (~67–72%) and minimum (~3.1–3.7%), respectively.

Fabrication And Mechanical Properties Of A Nanostructured Complex Aluminum Alloy By Three-Layer Stack Accumulative Roll-Bonding

Abstract A multi-layered complex aluminum alloy was successfully fabricated by three-layer stack accumulative roll bonding(ARB) process. The ARB using AA1050 and AA5052 alloy sheets was performed up to 7 cycles at ambient temperature without lubrication. The specimen processed by the ARB showed a multi-layer aluminum alloy sheet in which two aluminum alloys are alternately stacked. The grain size of the specimen decreased with the number of ARB cycles, became about 350nm in diameter after 7cycles. The tensile strength increased with the number of ARB cycles, after 6c it reached 281MPa which is about twice higher than that of the starting material. The microstructures and mechanical properties of a three-layer AA1050/AA5052 alloy fabricated by the ARB were compared to those of the conventional ARB-processed material.

Annealing texture of nanostructured steel-based composite

In this study, the evolution of annealing texture in nanostructured steel-based composite processed by accumulative roll bonding (ARB) was investigated. Textural evolution after post-annealing of ARB-processed samples was evaluated using X-ray diffraction. There was a texture transition in the ε-fiber during ARB process and post-annealing treatment. Average grain size of the sample before and after the post-annealing was 73nm and 1.8µm, respectively, and the microstructures were relatively uniform. It was found that with increasing the number of cycles, the volume fraction of the low angle grain boundary (LAGB) decreased and that of the high angle grain boundary (HAGB) increased. Also, the shear texture was dominant after the second and third ARB cycles, while for other samples, the rolling texture was dominant. The two-cycle and three-cycle samples obviously indicated a weak α-fiber and γ-fiber and a relatively strong ζ-fiber. It was proposed that the recrystallization led to a decrease in the α-fiber and γ-fiber and rolling texture components such as {111}〈110〉 and {111}〈112〉. On the other hand, the grain growth after recrystallization resulted in an increase in the α-fiber and γ-fiber and rolling texture orientations.

Investigation of nano-SiCp effect on microstructure and mechanical properties of Al/TiH2 foam precursor produced via ARB process

In this study, a new type of hybrid composite which can be potentially used as a foam precursor was achieved by 0.75 TiH2 and 0.75 nano-SiCp addition (wt%) between 5 pure Al strips, followed by 6 accumulative roll bonding (ARB) cycles at room temperature. The effect of nano-SiC particles addition on the resulting microstructures as well as the corresponding mechanical properties of the products was investigated. Al/0.75wt% TiH2 sheets were also fabricated by the ARB process to compare with the hybrid nanocomposite specimens. Scanning electron microscopy (SEM) and related EDS color images revealed that applying 6 ARB cycles led to fairly homogeneous distribution of the TiH2 and nano-SiCp and elimination of porosity between the particles and matrix. It was also found that the tensile strength of the Al/TiH2/nano-SiC hybrid composite was about 1.27 times higher than that of the Al/TiH2 precursor. SEM observation of fractured surfaces showed that the failure mechanism of the composite and nanocomposite was shear ductile rupture.