Number Of Accumulative Roll Bonding Cycles Research Articles

Mechanical, microstructural, and textural evaluation of aluminum-MWCNT composites manufactured via accumulative roll bonding at ambient condition

In the present study, aluminum-matrix composites reinforced by multi-walled carbon nanotubes (MWCNTs) were manufactured using the accumulative roll bonding (ARB) process. In the first step, MWCNTs were dispersed between two pieces of Al sheets that were then stacked together and rolled. In the second step, the above procedure was repeated for up to 12 cycles without adding MWCNTs. The microstructure and fracture surface of the composites were studied during various ARB cycles using optical microscopy (OM) and scanning electron microscopy (SEM). Also, the mechanical properties of the composites were measured employing tensile and Vickers hardness tests. More uniform dispersion of MWCNTs was found in the microstructure of the aluminum matrix after 12 ARB cycles. With an increase in the number of ARB cycles, the hardness of the composites was enhanced. The results indicated that after 11 cycles, both the elongation and tensile strength improved and strong interfacial bonding formed between MWCNTs and the Al matrix. However, the development of micro-cracks in the composite resulted in a decrease in elongation and tensile strength at the final cycle. SEM investigations of fracture surfaces revealed that the fracture mode of the composites changed from ductile to brittle in the final ARB cycle, while that of monolithic aluminum remained ductile for all ARB cycles. Texture analysis, also confirmed a transition from the initial recrystallized (Cube and Goss) texture to the ideal rolling texture, mainly with Copper and Dillamore components.

Mechanical properties, corrosion behavior, and cytotoxicity of biodegradable Zn/Mg multilayered composites prepared by accumulative roll bonding process

Zinc (Zn), magnesium (Mg), and their respective alloys have attracted great attention as biodegradable bone-implant materials due to their excellent biocompatibility and biodegradability. However, the poor mechanical strength of Zn alloys and the rapid degradation rate of Mg alloys limit their clinical application. The manufacture of Zn and Mg bimetals may be a promising way to improve their mechanical and degradation properties. Here we report on Zn/Mg multilayered composites prepared via an accumulative roll bonding (ARB) process. With an increase in the number of ARB cycles, the thicknesses of the Zn layer and the Mg layer were reduced, while a large number of heterogeneous interfaces were introduced into the Zn/Mg multilayered composites. The composite samples after 14 ARB cycles showed the highest yield strength of 411±3 MPa and highest ultimate tensile strength of 501±3 MPa among all the ARB processed samples, significantly higher than those of the Zn/Zn and Mg/Mg multilayered samples. The Zn and Mg layers remained continuous in the Zn/Mg composite samples after annealing at 150 °C for 10 min, resulting in a decrease in yield strength from 411±3 MPa to 349±3 MPa but an increase in elongation from 8±1% to 28±1%. The degradation rate of the Zn/Mg multilayered composite samples in Hanks’ solution was ranged from 127±18 µm/y to 6±1 µm/y. The Zn/Mg multilayered composites showed over 100% cell viability with their 25% and 12.5% extracts in relation to MG-63 cells after culturing for 3 d, indicating excellent cytocompatibility. Statement of significanceThis work reports a biodegradable Zn/Mg multilayered composite prepared by accumulative roll bonding (ARB) process. The yield and ultimate tensile strength of the Zn/Mg multilayered composites were improved due to grain refinement and the introduction of a large number of heterogeneous interfaces. The composite samples after 14 ARB cycles showed the highest yield strength of 411±3 MPa and highest ultimate tensile strength of 501±3 MPa among all the ARB processed samples. The degradation rate of the Zn/Mg multilayered composite meets the required degradation rate for biodegradable bone-implant materials. The results demonstrated that it is a very promising approach to improve the strength and biocompatibility of biodegradable Zn-based alloys.

Surface morphology and Rietveld refinement characterisation of aluminium/titania nanocomposite produced by atmospheric plasma spraying and accumulative roll bonding

ABSTRACT In this study, the nano-sized Titania (TiO2) particles were coated on an aluminum (Al) matrix using the atmosphere spraying method, and then the Al-TiO2 nanocomposite was fabricated by the accumulative roll bonding (ARB) process. The surface morphology evaluation by the field emission scanning electron microscopy (FESEM) revealed that TiO2 nanoparticles are uniformly spread and the amount of TiO2 nanoparticles decreased on the surface during the ARB process energy dispersive spectroscopy (EDS) mapping and X-ray diffraction (XRD) analysis demonstrated a decrease in the TiO2 phase while an increase in the Al phase in further cycles of the ARB process. Based on the atomic force microscopy (AFM) micrograph, the thicknesses of TiO2 particle clusters decreased from 1.26 μm to 238 nm by increasing the number of ARB cycles. The surface roughness values measured by the profilometer showed that the pressure of rolling has been an effect on reducing roughness to 96 micrometers, up to seven cycles of the ARB process. to calculate the Al crystallite size, TiO2 nanoparticles size, micro-strains and dislocation densities, the Rietveld refinement indicated that the increasing micro-strains and dislocation densities have led to reducing the Al crystallites and TiO2 particle clusters size to 234 and 40 nm, respectively.

Investigation of structure and mechanical properties under quasi-static and planar impact loading of aluminum composite reinforced with Al2O3 nanoparticles of different shape

We report on an investigation of the structure and mechanical properties under quasi-static and planar impact loading of Al-based nanocomposites reinforced with alumina nanoparticles of ball, plate and sheet shape fabricated through accumulative roll bonding (ARB) for 4 and 10 cycles. The distribution of the nanoparticles and structural characteristics of the matrix were revealed using transmission electron microscopy. The microhardness, ultimate and yield strengths and ductility under tension at the strain rate of 1 × 10−3 s−1 were measured as mechanical characteristics under the quasi-static loading. The maximum pressure of the impact compression, Hugoniot elastic limit and spall strength were calculated using the free surface velocity data recorded during the impact by aluminum flyer-plates with the impact velocity of 630 ± 30 m/s. Our results show that nanoparticles tend to agglomeration inside the composite. The size of agglomerates depends on the nanoparticle shape and a number of ARB cycles. Only the part of the ball-shaped nanoparticles can be distributed uniformly as separate nanoparticles after 10 ARB cycles. The introduction of the nanoparticles into aluminum assists in the structural refinement in the nanocomposites relative to alumina-free aluminum. This effect is mostly exhibited in the composite reinforced with the ball-shaped nanoparticles, some of which are distributed separately. The nanoparticle of different shape affects the mechanical properties ambivalently under both quasi-static and shock-wave conditions due to their various distribution in the matrix and different properties of the agglomerates. The spall strength decreases with the nanoparticle introduction because the particles and their agglomerates are the stress concentrators and crack origins.

High-strength and ductility bimodal-grained Al–Li/Al–Li–Zr composite produced by accumulative roll bonding

Microstructure evolution and mechanical behavior of bimodal-grained Al–Li/Al–Li–Zr laminated composite by accumulative roll bonding (ARB) were investigated. As-rolled Al–Li and as-annealed Al–Li–Zr sheets were bonded up to 5 cycles at room temperature. In the 5-cycle ARB processed Al–Li/Al–Li–Zr layered composite, straight and continuous bonding interfaces were formed between the soft Al–Li layers and hard Al–Li–Zr layers. No macro shear bands were observed, indicating that a uniform deformation occurred between different materials in the ARB process. A bimodal grain distribution of the micro-size elongated grains (1.3 μm) in the Al–Li–Zr layers due to the precipitation of Al3(Zr,Li) and the nanoscale ultra-fine grains (320.0 nm) in the Al–Li layers due to the recrystallization process was found. Microhardness in the Al–Li and Al–Li–Zr layers and tensile strength of the composite increased with the number of ARB cycles. However, the ductility first decreased at the 1-cycle ARB process then increased at 2–5 cycles ARB process. The best mechanical properties (UTS = 388 MPa and EL = 12.7%) were obtained in the 5-cycle ARB process. The high strength and ductility could be explained for the contributions from strain hardening, grain refinement, no macro shear bands and the formation of a bimodal grain size distribution.

Graphene oxide-reinforced aluminium-matrix nanostructured composites fabricated by accumulative roll bonding

Accumulative Roll Bonding (ARB) was used to fabricate Graphene Oxide-reinforced Al-matrix composites.Graphene Oxide reinforcement was suspended in a stabilized aqueous solution and applied, prior to each ARB cycle, through airgun spraying. Different concentrations (graphene oxide/milipore water) were used and for each concentration, samples produced have undergone up to 5 rolling cycles.Optical and electron scanning microscopies were used for microstructural characterization which revealed a non-homogenous deformation of the layers across the composite's thickness.Although the presence of graphene-oxide promoted an increase in the microhardness, higher values were obtained with its lowest concentration for similar samples. The number of ARB cycles and the direction of the tested sections also influenced the microhardness results since the 5-cycle samples and the rolling direction sections for all the samples achieved higher hardness results. Graphene Oxide revealed to be a major contributor to the increase of stiffness during bending of the tested samples.

Fracture Analysis of ARB-Processed CP-Ti Sheets Under Unidirectional Tensile Loading

The fracture behavior of commercially pure titanium (CP-Ti) processed by accumulative roll bonding (ARB) was investigated in this study. Monolithic and Ti-SiC composite samples were first produced by ARB process and then subjected to uniaxial tensile testing at room temperature. Two different ductile fracture mechanisms including shear dimple rupture and equiaxed dimple rupture were observed in the initial and final ARB cycles, respectively. The difference in the rupture mechanism was attributed to different stress states at the crack tip and different densities of metallurgical defects. A non-uniform distribution of dimple size was obtained for fracture surfaces of the samples processed by a low number of ARB cycles. This was attributed to the heterogeneity of microstructure in the primary ARB cycles. The fracture surface of the samples processed by high ARB cycles represented more uniform dimples. This was attributed to more homogenous microstructure in the final cycles. Moreover, SiC particles showed a major role in fracture of samples, so that they affected the size and depth of the dimples, as well as the number of ARB cycles in which the transmission of the fracture mechanism occurred.

A novel method for the fabrication of Al-matrix nanocomposites reinforced by mono-dispersed TiAl3 intermetallic via a three-step process of cold-roll bonding, heat-treatment and accumulative roll bonding

A novel method to fabricate aluminum metal-matrix composites reinforced by mono-dispersed TiAl3 intermetallic particles, by cold-roll bonding, heat treatment, followed by accumulative roll bonding (ARB), is demonstrated. Roll bonding of 1100-Al sheets inserted with Ti powder was carried out at room temperature with 50% thickness reduction. Complete conversion of the initial Ti particles into TiAl3 intermetallic was achieved by a post-rolling annealing treatment at 590 °C for 2 h, which results in the formation of coarse TiAl3 particles along the interface of the original 1100-Al sheets. Subsequent ARB process was applied to break up and disperse the TiAl3 phase, and after 5 cycles of ARB, an aluminum-matrix composite with mono-dispersed TiAl3 particles of submicron sizes was achieved. The Al matrix also undergoes dynamic recrystallization during the ARB process to result in a fine-grained microstructure (size less than 500 nm). The hardness, tensile strength and elongation of the Al/TiAl3 composite were found to increase with the number of ARB cycles. The tensile strength of the Al/TiAl3 composite after the 5th cycle reaches 400 MPa, which is significantly higher than the 300 MPa of monolithic 1100-Al processed in the same way. The tensile elongation of the Al/TiAl3 composite after 5 cycles of ARB exhibits a good value of ∼8%, with a ductile fracture mode. This is the first successful attempt to achieve Al-matrix nanocomposites reinforced by mono-dispersed TiAl3 intermetallic based on an ARB method.

Characteristics of Nano Grained AA1050/AA5052 Al Sheets Fabricated by Accumulative Roll-Bonding.

Accumulative roll-bonding (ARB) is the most appropriate process for sheet-shaped materials because it can be carried out readily by utilizing the conventional rolling apparatus. In this study, a nanostructured AA1050/AA5052 Al alloy sheet was successfully fabricated by four-layer stack ARB process. The ARB of AA1050 and AA5052 alloy sheets was performed up to 6 cycles without a lubricant at ambient temperature. The sample fabricated by the ARB was a multi-layer aluminum alloy sheet in which AA1050 and AA5052 layers are alternately stacked. The layer thickness of the each alloy became thinner and elongated to the rolling direction with the number of ARB cycles. The grain size decreased with increasing of the number of ARB cycles, after 6 cycles it became about 180 nm in thickness. The fraction of high angle grain boundaries increased with the number of ARB cycles. The tensile strength also increased with the ARB, it reached 305 MPa which is about 2.1 times that of the as-received AA1050. The mechanical properties of a multi-layer AA1050/AA5052 alloy fabricated by the ARB were compared to those of the other materials.

Dependency of annealing behaviour on grain size in Al–TiC composite produced by accumulative roll bonding

This work investigates the effect of grain size on annealing behaviour in both coarse-grained and ultrafine-grained Al–TiC composite processed by accumulative roll bonding (ARB). Microstructural analysis indicates that annealing behaviour of the specimens are essentially determined by the level of strain accumulation or number of ARB cycles, i.e., recrystallization phenomenon are accelerated by increasing the level of strain accumulation or number of ARB cycles. Microstructure analysis illustrates that annealing treatment at 200 or \(250{^{\circ }}\hbox {C}\) for the 1-cycle ARB-processed Al–TiC composite having coarse grains does not lead to the recrystallization phenomenon, indicating that only recovery appears. In contrast, partial recrystallization occurred after annealing at \(250{^{\circ }}\hbox {C}\) in the 7-cycle ARB-processed Al–TiC composite having ultrafine grains. Furthermore, annealing treatment significantly enhanced elongation for both ultrafine as well as coarse-grained Al–TiC composites in spite of the fact that yield and ultimate strength decreased during annealing treatment. The results proved that yield strength and tensile strengths for both 1-cycle and 7-cycle ARB-processed Al–TiC composites gradually decreased by annealing treatments between 200 and \(300{^{\circ }}\hbox {C}\). In contrast, ultimate elongation drastically improved by about 100% after annealing at the aforementioned conditions.

Microstructural Evolution of a Nanostructured Complex Copper Alloy Processed by Accumulative Roll-Bonding of Oxygen Free Copper and DLP.

The accumulative roll-bonding (ARB) process using different copper alloys of oxygen free copper (OFC) and dioxide low-phosphorous copper (DLPC) was performed up to six cycles at ambient temperature without lubrication. A complex copper alloy sheet'in which OFC and DLPC alloys are stacked alternately each other was successfully fabricated by the ARB process. The microstructural evolution and texture development of the complex copper alloy with proceeding of the ARB were investigated by electron back scatter diffraction (EBSD) measurement. The specimen after 1 cycle showed significantly inhomogeneous microstructure in thickness direction, however, the inhomogeneity decreased gradually with increasing the number of ARB cycles. In addition, the grains became finer with the proceeding of the ARB. Resultantly, after 6 cycles, the specimen exhibited an ultrafine grained structure in which the grains above 65% were surrounded by the high angle grain boundaries above 15 degrees. On the other hand, there was no difference in texture development between OFC and DLPC in almost all specimens. In addition, the texture development did not depend on positions in thickness direction; the rolling texture such as {112}<111> and {011}<211> components developed strongly at all regions.

Al-based magnetic composites produced by accumulative roll bonding (ARB)

Abstract Accumulative roll bonding (ARB) was used to fabricate Al/Ni (with two initial Ni thicknesses) and Al/Ni/Fe 3 O 4 composites. During ARB, Ni layers necked and fractured owing to the difference in flow properties of Al and Ni. In addition, large and elongated clusters of Fe 3 O 4 particles were broken into smaller ones and distributed gradually in Al matrix. After the fourth and sixth cycle, weak bonding and several pores were observed at particle/matrix interface while the bonding quality increased after the eighth cycle. Results show that after eight cycles, an Al-based composite with a satisfactorily magnetic behavior was produced. The Al/Ni (0.5) composite exhibited the highest tensile strength (182 MPa) with the highest value of saturation magnetization (13.47 emu/g). The relative permeability decreased with increasing frequency for a given number of ARB cycles. The Fe 3 O 4 particles caused the saturation magnetization to decrease and the critical frequency to increase due to the eddy current effects.

Formation of a dominant Dillamore orientation in a multilayered aluminum by accumulative roll bonding

In the present work, we report for the first time the formation of a dominant Dillamore orientation in a multilayered high-purity aluminum (99.99 %) subjected to an ultra-high von Mises strain of 11.2 by accumulative roll bonding (ARB). This multilayered aluminum with an average layer thickness of 180 nm was produced from an original aluminum sheet thickness of 100 μm. Microstructure and texture evolutions during ARB processes were investigated in detail and the formation of a dominant orientation is explained. The grain boundary spacing was observed to reduce with increasing number of ARB cycles. However, after 8 ARB cycles, the average grain boundary spacing was measured to be larger than the theoretical layer thickness. Also, a single and strong Cu orientation formed after an intermediate number (8–12) of ARB cycles, which rotated to a dominant Dillamore orientation with further ARB cycles. This is rationalized on the basis of three mechanisms: First, a homogeneous deformation causing lamella structure formation; second, the enhanced dynamic recovery of this pure aluminum through the movement of Y-type triple junction boundaries, resulting in grain coarsening; and third, the coarsening process eliminating the original few and small Brass and S lamellae and simultaneously enhancing the Cu and Dillamore orientations.

An Analytical Framework for Predicting the Limit in Structural Refinement in Accumulative Roll Bonded Nickel

The limit in structural refinement of lamellar bands (LBs) generated during accumulative roll bonding (ARB) of commercially pure nickel was investigated by transmission electron microscopy and transmission Kikuchi diffraction. A typical LB consists of an internal cellular substructure of low angle boundaries (LABs) bounded by two high angle boundaries (HABs) that are aligned parallel to the rolling plane. At low true strains (e 4.8; 6 to 10 ARB cycles), a homogenous distribution of well-defined, highly elongated LBs of average thickness 75 nm was generated throughout the entire thickness of the material. The thickness of these LBs decreased with increasing number of ARB cycles and reached a saturation thickness of ~75 nm after 6 to 8 cycles. A theoretical framework for the limit to LB refinement during ARB is presented based on the refinement rate due to the stored energy of deformation balanced by the growth rate caused by adiabatic heating. The analysis takes into account the unique features of LB structures and processing parameters.

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.

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.

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.

Electrochemical and Passive Behaviors of Pure Copper Fabricated by Accumulative Roll-Bonding (ARB) Process

In the present work, electrochemical and passive behaviors of pure copper fabricated by accumulative roll-bonding (ARB) process in 0.01 M borax solution (pH = 9.1) have been studied. Before any electrochemical measurements, evaluation of microstructure was obtained by Vickers microhardness, x-ray diffraction (XRD), and transmission electron microscopy. The results of microhardness tests revealed that microhardness values increased with the increasing number of ARB cycles. Also a sharp increase was seen in microhardness after the first ARB cycle, whereas mediocre additional increases were observed afterward up to the seven cycles. Moreover, XRD patterns showed that the mean crystallite size values decrease with the increasing number of ARB cycles. To investigate the electrochemical and passive behaviors of the samples, the potentiodynamic polarization, Mott-Schottky analysis and electrochemical impedance spectroscopy (EIS) were carried out. Polarization plots revealed that as a result of ARB, the corrosion behavior of the specimens improves compared with the annealed pure copper. Also, the Mott-Schottky analysis and EIS measurements showed that the increasing number of ARB cycles offer better conditions for forming the passive films with higher protection behavior, due to the growth of less-defective films.

Analysis of Strain Rate Sensitivity of Ultrafine-Grained AA1050 by Stress Relaxation Test

Commercially pure aluminum sheets, AA 1050, are processed by accumulative roll bonding (ARB) up to eight cycles to achieve ultrafine-grained (UFG) aluminum as primary material for mechanical testing. Optical microscopy and electron backscattering diffraction analysis are used for microstructural analysis of the processed sheets. Strain rate sensitivity (m-value) of the specimens is measured over a wide range of strain rates by stress relaxation test under plane strain compression. It is shown that the flow stress activation volume is reduced by decrease of the grain size. This reduction which follows a linear relation for UFG specimens, is thought to enhance the required effective (or thermal) component of flow stress. This results in increase of the m-value with the number of ARB cycles. Strain rate sensitivity is also obtained as a monotonic function of strain rate. The results show that this parameter increases monotonically by decrease of the strain rate, in particular for specimens processed by more ARB cycles. This increase is mainly linked to enhanced grain boundary sliding as a competing mechanism of deformation acting besides the common dislocation glide at low strain rate deformation of UFGed aluminum. Recovery of the internal (athermal) component of flow stress during the relaxation of these specimens seems also to cause further increase of the m-value by decrease of the strain rate.

Fabrication of nanoparticle strengthened IF steel via ARB process

Accumulative roll bonding (ARB) process was used in this study as a very effective method for fabrication of the nanoparticle strengthened IF steel. The microstructure of the produced composites after fourth cycle of the ARB process was exhibited a highly-uniform distribution of SiC nanoparticles in the IF steel matrix without any porosity. It was found that when the number of ARB cycles was increased, the tensile strength of the produced composites was improved, but their elongation was decreased at first step and then was increased at second step. The tensile strength of the composite was 6 times higher than that of the annealed IF steel. The findings also revealed that with increasing the number of cycles, first hardness rapidly increased and then dwindled.