Accumulative Roll Bonding Cycles Research Articles

Fabrication of Al/Mg/Al Composites via Accumulative Roll Bonding and Their Mechanical Properties.

Al(1060)/Mg(AZ31)/Al(1060) multilayered composite was successfully produced using an accumulative roll bonding (ARB) process for up to four cycles at an elevated temperature (400 °C). The microstructure evolution of the composites and the bonding characteristics at the interfaces between Al and Mg layers with increasing ARB cycles were characterized through optical microscopy, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). It was found that the grains of Al and Mg layers were significantly refined and Al3Mg2 and Al12 Mg17 intermetallic compound layers formed at the Al/Mg bonding interfaces. The strength increased gradually and the ultimate tensile strength (UTS) reached a maximum value of about 240 MPa at the third pass. Furthermore, the strengthening mechanism of the composite was analyzed based on the fracture morphologies.

Microstructure and Texture Evolution in Nickel during Accumulative Roll Bonding

Microstructure and texture evolution of commercially pure Ni processed by accumulative roll-bonding (ARB) up to eight cycles were studied using electron back scattered diffraction (EBSD). During ARB processing, the original coarse equiaxed grains were gradually transformed into refined lamellar grains along the rolling direction (RD). Shear bands started forming after three cycles. The fraction of low angle grain boundaries (LAGBs) increased after the first and second cycle because of orientation spreading within the original grains. However, their fraction decreased with the evolution of high angle grain boundaries (HAGBs) during subsequent deformations, until saturation was reached after six cycles. Overall, the typical deformation texture components (S, Copper and Brass) were enhanced up to six ARB cycles and then only Copper was further strengthened. At higher cycles a higher Copper concentration was found near sample surface than the interiors due to a high frictional shear of ARB processing.

Effect of Alumina Content on the Mechanical Properties of AA5083/Al2O3 Composites Fabricated by Warm Accumulative Roll Bonding

In the present study, aluminum metal matrix composites reinforced with alumina particles are fabricated through the warm accumulative roll bonding (ARB) process. The microstructure of the composites shows the excellent alumina particle distribution in the aluminum matrices after four cycles of ARB. The microstructure and mechanical properties of composites have been studied versus different contents of alumina particles by tensile test, Vickers microhardness test, and scanning electron microscopy. The results indicated that strength and average microhardness of the ARB-processed material improved by increasing volume percent of alumina particles.

An investigation in to the mechanical properties of CP Ti/TiO2 nanocomposite manufactured by the accumulative roll bonding (ARB) process

In this study, a commercially pure titanium (CP Ti) sheet was produced by the ARB process. Then, the mechanical properties of monolithic and nanocomposites specimens manufactured using 0.1, 0.3, and 0.5wt% TiO2 nanoparticles as the reinforcement were investigated at different ARB cycles. The results showed improvement in the mechanical properties of specimens with the addition of TiO2 nanoparticles, as their yield strength and ultimate tensile strength were increased by increasing the TiO2 nanoparticles percent. In this regard, the ultimate tensile strength of the monolithic specimen reached to 810MPa, while it was 980MPa, 1040MPa, and 1085MPa after applying 8 ARB cycles for 0.1wt%, 0.3wt% and 0.5wt% nanocomposite specimens, respectively. However, the ultimate tensile strength of the as-received CP Ti sheet was 285MPa. Moreover, the yield strength and the ultimate tensile strength were increased by increasing the number of ARB cycles and the total elongation; on the other hand, in the monolithic and nanocomposite specimens, it was decreased by increasing the number of ARB cycles. Grain refinements due to severe strain, work hardening and TiO2 nanoparticles reinforcements were the main causes accounting for the improved mechanical properties. Recovery and dynamic recrystallization were two phenomena observed via TEM studies in the ARB process, leading to the development of equiaxed grains in the final ARB cycles.

Role of powder preparation route on microstructure and mechanical properties of Al-TiB2 composites fabricated by accumulative roll bonding (ARB)

Accumulative roll bonding (ARB) was conducted up to seven cycles to fabricate Al-TiB2 particulate metal matrix composites. The reinforcing particles were prepared and used in three different processing conditions: as-received TiB2, mixed TiB2-Al and in-situ synthesized TiB2-Al. The mixed TiB2-Al powder was produced by milling of TiB2 with Al powder and in-situ synthesized TiB2-Al powder was prepared by mechanical alloying (MA) through inducing TiB2 particles in the Al with various composition of 10, 20 and 30wt% Al. Transmission electron microscope (TEM) and scanning electron microscope (SEM) were used to evaluate the microstructure of the produced composites. The composite obtained from the in-situ TiB2-Al powder showed the most uniform distribution of particles and exhibited the highest tensile strength of about 177MPa in comparison with the composites reinforced with the as-received TiB2 (156MPa) and mixed TiB2-Al powder (160MPa). After seven ARB cycles, an ultra-fine grained structure with the average size of about 300nm was obtained in the composite reinforced with in-situ TiB2-Al powder. The appearance of dimples in tensile fracture surfaces revealed a ductile-type fracture in the produced composites.

Development of Nano-Structured Metals Processed by Severe Plastic Deformation

Severe Plastic Deformation is the most promising technique which can produce Bulk Nano-Structured Materials (BNMs). Among various SPD techniques Accumulative Roll Bonding (ARB) and Equal Channel Angular Pressing (ECAP) have a broad significance due to its unusual mechanical performance. In this paper, the principle and merits of ARB and ECAP technique are pointed out, and also a model based on simulation is established for investigating SPD developments. Pure Copper after sixteen numbers of ARB cycles discloses greater strength by more rises in ductility as compared to that of coarse-grained metals. Similarly in pure Titanium after five numbers of ARB cycles incredibly substantial increase in strength together with an only small decrease of ductility has obtained. The result shows that it is achievable to get high strength, except only with significantly reduced ductility.Additionally, a simulated model, founded on lattice defect kinetics has established. This model holds true parameters like dislocation density, vacancy concentration, grains size, etc., found appropriate for the grain refinement throughout and after the SPD process of simulation. It presents quantitatively consistent outcome for the hardening performance and micro-structural development in pre and post SPD deformation. The new results of SPD-processed nano-structured materials are elucidated, particularly considering viable uses. The advantages of nano-structured metals and alloys mostly for aerospace engineering, automotive engineering, electronic industry and for biocompatible are pointed out such as improved hydrogen storage kinetics (Mg-alloys) for fuel cell technology, superior magnets, Ti, Mg-alloys for prostheses, implants, and stents, etc.

Microstructure, mechanical properties and electrochemical behavior of AA1050 processed by accumulative roll bonding (ARB)

In this work, the effect of ARB process on the microstructure, mechanical properties and electrochemical behavior of AA1050 was investigated. X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images were used for measuring the crystallite and grain sizes of samples. TEM micrographs and XRD plots revealed that with increasing the number of ARB cycles, the grain/crystallite size of sample decreased and eventually nanostructured AA1050 achieved after 9 cycles of ARB with average crystallite size around 91 nm. Results of the microhardness and tensile tests demonstrated that mechanical properties of samples improved as the number of ARB cycles increased. Scanning electron microscopy (SEM) micrographs of fracture surfaces illustrated that ductile fracture occurred in all samples. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) results showed that passive behavior of the ARBed samples improves compared to the annealed AA1050 sample. Moreover, the Mott–Schottky analysis and EIS measurements showed that increasing the number of ARB cycle offer better conditions for forming the passive films.

Microstructural evolution and mechanical properties on an ARB processed IF steel studied by X-ray diffraction and EBSD

Accumulative Roll Bonding (ARB) is one of the so-called severe plastic deformation (SPD) processes, allowing the production of metals and alloys with ultrafine (micro-nano) structures. Materials with ultrafine grains present attractive properties like the simultaneous increase in strength and ductility. Our interest in these materials is focused on their microstructural evolution during ARB processing, eventually responsible for the enhancement of those mechanical properties.In the current work we follow the evolution of the microstructure in an interstitial-free (IF) steel deformed by ARB after consecutive processing cycles, by means of Electron BackScatter Diffraction (EBSD) and X-ray diffraction (XRD). Particularly, we present results related to texture, grain (GS) and domain sizes, grain boundary character, density of Geometrically Necessary Dislocations (GND), Grain Orientation Spread (GOS), lattice parameters, microstrain, dislocation density and their spatial arrangement.After 5 ARB cycles the system shows a microstructure constituted mainly by submicrometric grains with high angle boundaries and low presence of dislocations inside the grains.

Shear punch test in Al/Alumina composite strips produced by powder metallurgy and accumulative roll bonding

Al-0.2, 0.4, and 0.8wt% alumina composites were manufactured via powder metallurgy and hot rolling techniques successfully followed by the accumulative roll bonding (ARB) process. Microstructural characterization of the composite strips thus fabricated was carried out using optical and scanning electron microscopy. The shear punch test (SPT) and Brinell hardness measurements were used to investigate the mechanical properties of the ARB-ed samples, which revealed that alumina powder particles became more uniformly distributed with increasing number of ARB cycles. Regarding porosity, no pores could be detected among the Al and alumina particles after the fifth ARB cycle. The results also indicated that shear elongation percentage of the specimens decreased before it gradually increased with increasing number of ARB cycles while their shear strength and hardness improved.Another finding of the present study was that the shear failure surfaces of the hot rolled strips exhibited a ductile fracture with a dimple structure while those processed by the ARB technique demonstrated shear flattened surfaces.

Strengthening Mechanisms and Electrochemical Behavior of Ultrafine-Grained Commercial Pure Copper Fabricated by Accumulative Roll Bonding

In this study, the four-cycle accumulative roll bonding (ARB) process at room temperature was successfully used for grain refining in commercial pure copper. Atomic force microscopy (AFM) images revealed that the average grain size reduced from about 26 µm in the unprocessed material to about 180 nm after four cycles of ARB. Also, transmission electron microscopy image indicated that the average grain size reached to 200 nm after four cycles. The yield strength of the ultrafine-grained pure copper after fourth cycle (360 MPa) was about 400 pct higher than that of the annealed unprocessed sample (70 MPa). The contribution of dislocations in strengthening of the pure copper decreased from ~30 to ~3 pct whit increasing the number of ARB cycles from 1 to 4. Scanning electron microscopy micrographs of fractured surfaces of the tensile test specimens revealed that ductile fracture of annealed sample with deep equiaxed dimples replaced by shear ductile rupture with shallow and small elongated dimples in ARB-processed samples. Moreover, electrochemical impedance spectroscopy and Mott–Schottky analysis showed that the electrochemical behavior improved by increasing the number of ARB cycle.

Corrosion behavior assessment of finely dispersed and highly uniform Al/B4C/SiC hybrid composite fabricated via accumulative roll bonding process

For the first time, the corrosion behavior of Al/B4C/SiC hybrid composites fabricated by accumulative roll bonding (ARB) processes was investigated. The produced hybrid composites which were consisted of 1 and 2.5wt.% of B4C and SiC reinforcement particles by nine ARB cycles showed a homogeneous distribution and strong bonding between particles and matrix without any porosity. In order to characterize the corrosion behavior of the produced hybrid composites, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization in 3.5wt.% NaCl solution were carried out. Moreover, for the better understanding of corrosion resistance of the produced hybrid composites, the EIS and potentiodynamic polarization tests were carried out on ARBed 1050 Al alloy (which was used as matrix) after 3 and 9 cycles. The results of EIS and potentiodynamic polarization curves revealed that employing the ARB process has led to higher polarization resistance and lower corrosion current density of the produced hybrid composites as well as 1050 Al alloy.

Microstructure and Mechanical Properties of Accumulative Roll-Bonded AA1050A/AA5005 Laminated Metal Composites

Laminated metal composites (LMCs) with alternating layers of commercial pure aluminum AA1050A and aluminum alloy AA5005 were produced by accumulative roll-bonding (ARB). In order to vary the layer thickness and the number of layer interfaces, different numbers of ARB cycles (4, 8, 10, 12, 14 and 16) were performed. The microstructure and mechanical properties were characterized in detail. Up to 8 ARB cycles, the ultrafine-grained (UFG) microstructure of the layers in the LMC evolves almost equally to those in AA1050A and AA5005 mono-material sheets. However, the grain size in the composites tends to have smaller values. Nevertheless, the local mechanical properties of the individual layers in the LMCs are very similar to those of the mono-material sheets, and the macroscopic static mechanical properties of the LMCs can be calculated as the mean value of the mono-material sheets applying a linear rule of mixture. In contrast, for more than 12 ARB cycles, a homogenous microstructure was obtained where the individual layers within the composite cannot be visually separated any longer; thus, the hardness is at one constant and a high level across the whole sheet thickness. This results also in a significant higher strength in tensile testing. It was revealed that, with decreasing layer thickness, the layer interfaces become more and more dominating.

Production of Al/Sn multilayer composite by accumulative roll bonding (ARB): A study of microstructure and mechanical properties

In this research, the Al/Sn composites, a part of the plain bearing components, were produced by the accumulative roll bonding (ARB) up to eight cycles. By increasing the number of ARB cycles, the layered structure became unstable. The deformation of two constituent metals was almost uniform until the second ARB cycle. The obvious necking, wavy appearance and rupture of the Al layers were observed after the third ARB cycle. The final microstructure consists of a uniform distribution of the hard Al phase within the soft Sn matrix. The maximum tensile strength reached 155MPa after two cycles, which was around 2.2 times higher than that of the pure Al; thereafter, it decreased until the fourth cycle and then increased until the last cycle. The tensile elongation of the produced composites decreased to about 3% and remained approximately constant until the last cycle. The hardness of the individual layers increased gradually by increasing the number of ARB cycle. The tensile fracture surfaces revealed dimples in both Al and Sn after the first-to eighth ARB cycles. The XRD results showed that no new phase has been formed during ARB.

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.

A new strategy to simultaneous increase in the strength and ductility of AA2024 alloy via accumulative roll bonding (ARB)

Nano/ultrafine grained (NG/UFG) AA2024 alloy produced by accumulative roll bonding (ARB) showed high strength (420MPa) and very limited elongation (about 1.3%). A new strategy via ARB was developed to improve elongation (about 10%) of AA2024 alloy with a relatively high strength (365MPa). The present strategy produced a bimodal structure consisting of coarse and ultrafine elongated grains in comparison to the UFG alloy. Electron backscattered diffraction (EBSD) revealed that after 4 ARB cycles, the fraction of high angle grain boundaries and mean misorientation angle of the boundaries in the bimodal grain structure were 61% and 27.34°, respectively, in comparison to that of annealed (54% and 24.96°) and UFG (79% and 34.27°) alloy. The crystallographic texture results indicated that, unlike the annealed AA2024 alloy, the intensity of Brass {011}<211> and S {123}<634> components remarkably increased in the UFG and bimodal alloy. Scanning electron microscopy (SEM) observations demonstrated that failure mode in bimodal alloy was ductile fracture with a combination of deep and shallow dimples.

Microstructure and Mechanical Properties of Mg/2 wt.%SiCp Nanocomposite Fabricated by ARB Process

Magnesium matrix nanocomposites (MMNC, the same below) containing 2 wt.% nanosized SiCp were fabricated through accumulative roll bonding (ARB). The microstructure and mechanical properties of Mg/2 wt.%SiCp nanocomposites are reported for various ARB cycles. To evaluate microstructure of the nanocomposites, the field emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), and transmission electron microscope (TEM) were applied. After fourteen ARB cycles, the nanocomposite showed a homogeneous distribution of reinforcements and a significant reduction in average matrix grain size. Meanwhile, the nanocomposite revealed a higher percentage of recrystallization and lower intensity of basal texture as compared to monolithic Mg. Mechanical properties were investigated through tensile and microhardness tests. The strength and elastic modulus and microhardness of Mg/2 wt.%SiCp were found to be improved significantly from eight ARB cycles and reach maximum values at fourteen ARB cycles. The ultimate tensile strength, yield strength, microhardness, and elastic modulus of Mg/2 wt.%SiCp are considerably increased by 17.6%, 61.0%, 72.7%, and 80.8% as compared to raw Mg, respectively.

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.

The Effect of Al2Cu Precipitate Size on Microstructure and Mechanical Properties of Al-2 wt.%Cu Alloys Fabricated by ARB

The effect of pre-existing precipitates on microstructure evolution, mechanical properties, and fracture behavior of Al-2 wt.%Cu alloy during accumulative roll-bonding (ARB) process was investigated. Aging treatment was done on Al-2 wt.%Cu alloy in order to produce the nano-particle size precipitates. The microstructure evolution was studied using transmission electron microscope and electron backscattering diffraction (EBSD), and mechanical properties were investigated using tensile test and Vickers microhardness measurements. The fine precipitates were formed after the aging process and improved the mechanical properties in the Aged-specimen compared to the solution-treated (ST) specimen. The EBSD analysis showed that the grain size after 6-cycle ARB process has decreased down to 650 and 420 nm for the ST-ARB and the Aged-ARB specimens, respectively. Also, with increasing the number of the ARB cycles, the fraction of HAGBs is increased in both the ST and Aged-specimens. It was found that as the number of cycles increased, the Vickers microhardness value and the yield strength and the tensile strength increased. The scanning electron microscope (SEM) images showed that as the number of the ARB cycles increased, the dimple size became smaller.

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.