ARB Cycles Research Articles

Investigation of corrosion behavior of Al–TiO2 nanocomposite produced using air plasma spray and accumulative roll bonding method

This work is an attempt to study the Al–TiO2 nanocomposite properties applying accumulative roll bonding process. For this purpose, nano Titania powder was first coated on aluminum foil by air plasma spraying process. The nanocomposite was then fabricated in one, two, three, five, and seven cycles by ARB. To investigate the effect of ARB process cycles on an Al-5% wt. TiO2 nanocomposite, characterization tests including XRD, quantitative XRD analysis by MAUD software, FESEM, EDS, electrochemical impedance, and TAFEL polarization tests were performed on the samples. The results indicate that the crystallite size reduced from 156 to 31 nm and the dislocation density quadrupled in the composite. The results of XRD analysis showed an increase in the dislocation density in the composite when the number of cycles increases. The reduction of crystallite size and increase of the grain boundaries have caused a sudden increase in the dislocation density. As the ARB cycle increases, the local porosity decreases and the local cracks due to the separation of the titanium sprayed droplets disappear in the matrix phase, and the reinforcing phase has more diffusion in the matrix. With the increase of ARB cycles, the percentage of titanium and oxygen elements on the surface was decreasing, but they remained until the last cycle. Among the non-rolled and rolled samples in different cycles, ARBed samples after 1 cycle and 5 cycles had not only the lowest and highest corrosion current densities but also the highest and lowest total resistance (Rt), respectively. This indicates max corrosion resistance due to the decrease in defect and porosity resulting from plasma spray and min corrosion resistance as a result of formation of galvanic cell between Al-matrix and Ti-reinforcing particles, respectively.

Microstructural investigation of an Al–Cu lamellar nanocomposite produced by accumulative roll bonding process under the heat treatment condition: an analytical, experimental, and finite element study

The microstructural evolution of a heat treated and accumulative roll bonded (ARBed) Al–Cu composite was studied using different metallurgical methods. Alumina particles were also added to the matrix of the composite to observe the effect of particles on the formation of the intermetallic compounds (IMCs) during heat treatment. Before heating, it was seen that Cu layers fractured in the Al matrix during the ARB process and the mean grain size of the composite reached less than 500 nm after the sixth ARB cycle. Optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) investigations were conducted on the Al–Cu composite to monitor microstructural changes before and after the heat treatment process. It was observed that diffusion of the Al and Cu atoms occurred during heat treatment of the composite. Moreover, SEM investigations revealed that only two kinds of IMCs namely AlCu and Al4Cu9 thrived through the matrix of the composites. Gibbs's free energy for the components was then evaluated and confirmed the formation of the IMCs between the metallic layers. A finite element method (FEM) was also employed to determine Cu layer thickness changes and fracture behavior of the Al–Cu ARBed materials. It was seen that induced pressure by the rollers made considerable changes in the Cu thickness. Also, the first fracture mode (mode Ⅰ) was determined to be more destructive as compared to the second fracture mode (mode ⅠⅠ) for the heat treated materials.

Improving the fracture toughness of multi-layered commercial pure aluminum via warm accumulative roll bonding

In this study, the fracture toughness of the multi-layered commercial pure aluminum samples (AA1050) prepared by warm accumulative roll bonding (WARB) was investigated for the first time. Based on the ASTM E561 standard, the R-curve method was utilized to measure the plane stress fracture toughness. Compact tension (CT) samples were prepared from the sheets that were processed by different ARB cycles. Mechanical properties, microstructure, and fracture surfaces of the CT samples were studied by uniaxial tensile test, electron backscatter diffraction (EBSD), and scanning electron microscopy (SEM), respectively. By increasing the number of WARB cycles, fracture toughness increased; after five cycles, 78% enhancement was observed compared to the pre-processed state. A correlation was seen between the fracture toughness variations and ultimate tensile strength (UTS). WARB enhanced UTS up to 95%, while the grain size showed a reduction from 35 to 1.8 μm. Measured fracture toughness values were compared with the room temperature ARB outcomes, and the effective parameters were analyzed. Fractography results indicated that the presence of tiny cliffs and furrows and hollow under fatigue loading zones and shear ductile rupture in the Quasi-static tensile loading zone.

Fabrication of Bimetal Aluminum-5 % Alumina-Bromine Composites by Warm Accumulative Roll Bonding

Abstract In this study, aluminum alloy 1050 and brass 70/30 are used to fabricate reinforced bimetal aluminum-5 % alumina (Al2O3)-bromine composites via a warm accumulative roll bonding (WARB) process. The aluminum and bromine strips were firstly welded together with the RB process up to 6 ARB cycles. In the WARB process, the rolled samples were preheated at 280°C for 7 min before each rolling cycle. The mechanical properties of the aluminum-Al2O3-bromine composite samples were evaluated in comparison to aluminum-5 % Al2O3 and bromine-5 % Al2O3 accumulative roll-bonded single-metal composite samples. It was shown that aluminum and brass deform in a similar way in the aluminum-Al2O3-bromine composites up two ARB cycles and then bromine layers began to neck. The average strength of the aluminum-Al2O3-bromine composites is higher than that of these two single-metal metal matrix composites. It was shown that the ductility and strength of the fabricated composite samples enhanced with the WARB cycles. Moreover, the fracture surfaces of bimetal composites have been studied by scanning electron microscopy.

Fabrication of Al/Cu Composite Reinforced with AISI 304 Stainless Steel Wires Through Accumulative Roll Bonding and Evaluation of Their Mechanical Properties

In the present study, a multilayer Al/Cu composite reinforced with AISI 304 stainless steel wires was fabricated through an accumulative roll bonding process. The microstructure and bonding integrity of different layers were investigated using optical and scanning electron microscopy. Mechanical properties of the produced composite samples were evaluated by tensile testing and micro-hardness measurements. Results showed that after six cycles of ARB processing, a multilayer Al/Cu composite with uniform distribution of Cu and AISI304 wires in an Al matrix is produced. Also, the results of tensile testing indicate that both the strength and elongation of the fabricated composite decrease with increasing the ARB cycle. Scanning electron microscopy analysis of the fractured surfaces of tensile specimens showed a combination of ductile rupture with deep dimple forming and cleavage fracture at different composite layers.

EFFECT OF TIO2 PARTICLES ON THE MECHANICAL AND MICROSTRUCTURAL EVOLUTION OF HYBRID ALUMINUM-BASED COMPOSITES FABRICATED BY WARB

In this study, the effect of powder particle contents on the mechanical properties of aluminum-based hybrid composites produced by warm accumulative roll bonding (WARB) process was investigated. Three hybrid composite groups with fully annealed AA1060 strips, 1[Formula: see text]wt.% of MnO2 and 0, 7.5 and 15[Formula: see text]wt.% of TiO2 were first roll-bonded and then the ARB process continued up to eight rolling cycles. In the WARB process, the samples were preheated at 300∘C for 5[Formula: see text]min before each rolling cycle. It was realized that increasing the number of ARB cycles with 0 and 7.5[Formula: see text]wt.% of TiO2 particles improved the uniformity of TiO2 particles distribution in the aluminum matrix. Also, in samples with high contents of TiO2 particles (15%), TiO2 clusters converted into small clusters with a better distribution through the aluminum matrix. Also, by increasing the number of cycles and TiO2 wt.% up to 15%, the tensile strength, elongation, tensile toughness and average Vickers microhardness of hybrid composites were increased first and decreased then. Moreover, the effects of ARB cycles and TiO2[Formula: see text]wt.% on the fracture surface of hybrid composites have been studied by scanning electron microscopy (SEM). It was found that all the samples fabricated with one and two ARB cycles exhibited a typical ductile fracture containing deep dimples, whereas by increasing the TiO2[Formula: see text]wt.% and ARB cycles, a combination of ductile and shear ductile fracture have been detected in the fracture behavior.

Microstructural Changes with Annealing of a Nanostructured Al Alloy Severely Plastic Deformed by Four-Layer Stack Accumulative Roll-Bonding Process.

Microstructural changes with annealing of a nanostructured complex aluminum alloy fabricated by 3 cycles of four-layer stack ARB process using different Al alloys were investigated in detail. The four-layer stack ARB process using AA1050, AA5052 and AA6061 alloy sheets was performed up to 3 cycles without a lubricant at room temperature. The sample fabricated by the ARB is a multi-layer aluminum alloy sheet in which the AA1050, AA5052 and AA6061 aluminum alloys are alternately stacked to each other. The layer thickness of 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, and became about 160 nm in thickness after 3 cycles. The complex Al alloy still showed ultrafine grained microstructure to annealing temperature of 300 °C, but it had a heterogeneous structure containing both the ultrafine grains and the coarse grains due to an occurrence of discontinuous recrystallization after 350 °C.

Effect of Electrically Assisted Accumulative Roll Bonding (EARB) Process on the Mechanical Properties and Microstructure Evolution of AA5083/Al2O3 Composites

Abstract In this study, electrically assisted accumulative roll bonding (EARB) process has been proposed and applied to produce metal matrix composite (MMC: AA5083/-1 % aluminum oxide [Al2O3]). This process can be used to fabricate the MMCs needed in various industries such as automobile and aerospace with appropriate mechanical properties. The alloy was deformed in various electricity current levels, i.e., at 0, 100, 200, and 300 A up to six ARB cycles (ε = 4.8). The mechanical properties of the deformed material have been measured by a tensile test, Vickers microhardness test, and scanning electron microscopy. Microstructure evolution during the EARB cycles leads to improvement of the strength and elongation amount of samples. According to the results obtained, uniform dispersion of Al2O3 particles improves both the strength and tensile toughness of the composites. Also, it was established that the electricity current had a significant effect on the mechanical and microstructure properties of the manufactured MMCs. High strength, low elongation, and high average Vickers microhardness were obtained for the material processed at lower current intensities. Whereas, by increasing the electricity current intensity up to 300 A, the tensile toughness and elongation amplitudes improved considerably.

The Simulation of Shear Angle and Deformations of Cu/Al Composite Sheets during Accumulated Roll Bonding

The present simulation study gives shear angle distribution and deformations, there in the effect of severe plastic deformation due to the accumulated roll bonding on the crystalline structure of materials is discussed. In the analysis, the classical metal plasticity models with a von Mises yield surfaceand thePLASTIC, HARDENING = ISOTROPIC as keyword in ABAQUS, were employed. The equivalent strain, εeq, imposed by rolling is defined as micro-hardness was used to characterize the mechanical properties. After four cycles, the mechanical properties were improved with increasing ARB cycles.

Investigation of microstructure and texture evolution of a Mg/Al laminated composite elaborated by accumulative roll bonding

The microstructure and texture of an Al1050/AZ31/Al1050 laminated composite fabricated by accumulative roll bonding at 400 °C up to 5 cycles are investigated using Electron BackScatter Diffraction, neutron diffraction, microhardness measurements and tensile tests. EBSD analysis has shown that ARB processing led to microstructural refinement with equiaxed grain microstructure in AZ31 layers and to the development of elongated grains parallel to the rolling direction in Al 1050 layers. No new phases formed at the bond interface after the first ARB cycle while Mg17Al12 and Mg2Al3 phases appeared after subsequent cycles. During the ARB processing, a typical strong basal (0002) texture is observed in AZ31 layers along with a weak rolling texture showed in Al 1050 layers with a dominant Rotated Cube {001}〈110〉 component. The microhardness of Al1050/AZ31/Al1050 laminated composite increased with increasing ARB cycles and almost saturated after five ARB cycles. The yield strength and ultimate strength increased gradually between 1 and 3 ARB cycles due to the strain hardening and grain refinement. They decreased with further increasing of the ARB cycles because of crack and failure of the MgxAly intermetallic compounds which developed during 4th and 5th ARB cycles. The deformation behavior of the laminated composite becomes rather similar to the behavior of AZ31 alloy that underwent a dynamic recrystallization during processing.

Evolution of Nanostructure Through Thickness of Deoxidized Low-Phosphorous Copper by Three-Layer Stack Accumulative Roll-Bonding.

A nanostructured deoxidized low-phosphorous copper (DLPC) was fabricated by three-layer stack accumulative roll-bonding process. Three sheets of 1 mm in thickness, 30 mm in width and 300 mm in length were stacked up and roll-bonded to thickness of 1 mm by two-pass cold rolling. The bonded sheet was cut in three pieces of same length, then stacked up and roll-bonded to the thickness of 1 mm again. The evolution of nanostructure through thickness with three-layer stack ARB were investigated in detail. It was found that the microstructure has been evolved from a dislocation cell structure to a nano grained structure with the proceeding of ARB cycles. The average grain thickness of 45 μm in initial decreased to 170 nm after 7 cycles of the ARB. The heterogeneity in microstructure through thickness was also largely decreased by the ARB. These results suggest that three-layer stack ARB is an effective process for a formation of nanostructure of DLPC alloy.

Effect of ARB Cycle Number and Second Phase Content on Mechanical properties and Microstructure of Pb–Ag Composite

A solid state method has been found for manufacturing of lead–silver composites for use as anodes in electrowinning production. Mechanical properties and microstructure of composite were characterized via peeling, tensile and microhardness tests, and scanning electron microscopy, transmission electron microscopy and fractography. Based on the peeling test results, maximum bond strength was achieved in the presence of 0.125 wt% of Ag (1.8 N/mm). Best mechanical properties were achieved in the Pb–0.5 wt% Ag composite after 10 ARB cycles by the enhanced tensile strength rising up to 50%, yield strength up to 170%, shear strength up to 63% and hardness up to 2.6 times higher, and the strain decreasing to 68% lower. These advanced properties led to higher stiffness and considerable enhancements in dimensional stability of the anodes and they improved creep characteristics. The advanced properties of the processed Pb–Ag composite anodes could be introduced as certification for slower anode failure, upkeep, surcharge and capital expenditure of industries with essential lead anode requirement.

Effect of accumulative roll bonding process on textural evolution and its comparison with normal rolled AA7005 aluminum alloy

In the present work, texture evolution of AA7005 aluminum alloy during the accumulative roll bonding and conventionally rolled was investigated by X-ray diffraction. It was found that the dominant texture components of both samples were Brass, Copper, Rotated Cube and Goss components, but the ARB texture evolution was quicker and displayed complex features. When the number of ARB cycle increased, the intensity of texture components decreased at the second and third pass, then enhanced at the fourth pass, and finally decreased. During the ARB process there was a texture transition at the second and third pass from Brass and S to Rotated Cube components due to the shear texture which formed on the surface region and moved to the center during the next pass. The enhancement of texture intensity at the fourth pass might be attributed to the formation of nano shear bands. The texture intensity decreasing at final cycle was correlated to redundant shear strain and continuous recrystallization during the high ARB passes.

Mechanical properties, bond strength and microstructural evolution of AA1060/TiO2 composites fabricated by warm accumulative roll bonding (WARB)

AbstractIn the present study, aluminum metal matrix composites reinforced with 5 % volume fraction of TiO2 particles were manufactured via warm accumulative roll bonding (WARB). The mechanical properties and microstructural evolution of composites fabricated by 1, 3, 5, 7, and 9 cycles of WARB were studied with application of tensile, peeling, and Vickers micro-hardness tests. Microstructural evolution during ARB cycles led to improvement of the strength and elongation properties of the samples. According to the results, uniform distribution of TiO2 clusters improved both the strength and tensile toughness of the composites. Finally, introduction of TiO2 particles into the Al matrix via WARB would allow fabricating particle-reinforced Al alloy with high uniformity and significantly enhance the mechanical properties and bond strength. Moreover, after the tensile and peeling tests, the fracture and peeling surfaces of the samples were studied at various WARB cycles using scanning electron microscopy.

Mechanical Properties and Microstructural Evolution of Bimetal 1050/Al2O3/5083 Composites Fabricated by Warm Accumulative Roll Bonding

In this study, a warm accumulative roll bonding process was used to produce a 1050/5% Al2O3/5083 composite from AA1050 and AA5083 sheets. Firstly, the raw materials were roll-bonded and then rolled up to five accumulative rolling cycles by preheating for 5 min at 280°C before each cycle. The mechanical properties of the ARBed bimetals were evaluated in comparison with 1050/5% Al2O3 and 5083/5% Al2O3 roll-bonded single-metal metal matrix composites (MMCs). It was found that two different layers of the bimetal sheet (1050/5% Al2O3/5083 composite) were deformed in a nearly identical way during the first three cycles. After that, the 5083 layers started necking. The strength of the bimetal samples was superior to the average of these two single-metal MMCs. Furthermore, the strength and ductility of the ARBed bimetal improved by ARB cycles. Finally, the fracture surfaces of the bimetal composite were studied at all ARB cycles by scanning electron microscopy.

Enhanced fatigue lives in AA1050A/AA5005 laminated metal composites produced by accumulative roll bonding

In this work laminated metal composites with alternating layers of commercial pure aluminum AA1050A and aluminum alloy AA5005 were produced by ARB. In order to vary the layer thickness and the number of interfaces different numbers of ARB cycles (4, 8 and 12) were applied. Subsequently, fatigue tests were performed and the related deformation and damage mechanisms were investigated. At high amplitudes crack growth occurs very straight through the whole sheet and is more or less unaffected by the interfaces of the individual layers in the composite. At lower amplitudes, where pronounced grain coarsening of the AA1050A layers occurs, the cracks deflect in front of the AA5005 layers and propagate in the coarsened AA1050A layers parallel to the bonding plane and the loading direction. Contrary to the composite, in both conventionally ARB processed AA1050A and AA5005 mono-material sheets grains are only locally coarsened around the crack tip and the fatigue cracks propagate very straight through the sheet width. Compared to AA1050A mono-material ARB sheets fatigue life and the cyclic stability are clearly enhanced in all composites.

Effect of grain refinement on mechanical and electrochemical properties of ultra-fine grained AA1050 fabricated via ARB process

Effect of ARB process on mechanical and electrochemical properties of AA1050 was investigated. AFM images represented nano-scale roughness of ARBed samples which decreased with increasing the number of ARB cycles. TEM micrographs indicated that with increasing the cycle number of ARB process, the grain size of samples decreased and UFG structure achieved. Based on TEM images, final grain size after nine cycles of ARB reached to 270nm. Results of tensile test showed that as the number of ARB cycles increased, the mechanical characterization of samples improved. Potentiodynamic polarization and EIS plots revealed the enhancement of passive behavior of samples with increasing the cycle number of ARB process. Also, semiconducting behavior of passive films was investigated by using the Mott–Schottky analysis. The outcomes revealed that passive films of all samples behaved as n-type semiconductor, and donor density decreased with increasing cycle number of ARB process. Compared to annealed sample, it was found that electrochemical behavior of the ARBed samples improved by increasing the processing cycle number, which is due to grain refinement.

Global and local strain rate sensitivity of bimodal Al-laminates produced by accumulative roll bonding

Laminated metallic composites of 5 mm thickness, with a bimodal grain size distribution and alternating layers of commercial purity aluminum (Al99.5) and high purity aluminum (Al99.999) were successfully processed by accumulative roll bonding at room temperature up to 8 cycles. With increasing number of ARB cycles the layers of commercial purity aluminum become ultrafine-grained, whereas the grain size in the high purity aluminum remains clearly above 1 μm. The mechanical properties of the laminates were investigated by compression testing with strain rate jumps and by nanoindentation using continuous stiffness method and nanoindentation strain rate jump tests. Thereby the strain rate sensitivity was determined both globally, proving the bulk laminate material, and locally, proving the single layers of the laminate. It was found that the local strain rate sensitivity of the ultrafine-grained Al99.5-layers is increasing up to 4 ARB cycles, while the local strain rate sensitivity of the coarse grained Al99.999-layers remains rather constant independently of the number of cycles. In contrast to that, the global strain rate sensitivity of the bulk laminate increases up to 8 cycles without saturation. Thermally activated annihilation of dislocations at the grain boundaries and interfaces between the coarse grained and ultrafine-grained layers is proposed in order to interpret the findings.

Passive Behavior of Ultra-Fine-Grained 1050 Aluminum Alloy Produced by Accumulative Roll Bonding in a Borate Buffer Solution

In this study, the effect of the ARB process on the passive behavior of ultra-fine-grained 1050 aluminum alloy in a borate buffer solution (pH 6.0) has been investigated. The result of the microhardness tests revealed that the microhardness values increase with an increasing number of ARB cycles. The potentiodynamic polarization plots revealed that the higher number of cycles for the specimens proceeds with the ARB process rather than annealing yield to lower corrosion and passive current densities and more noble corrosion potential values. Moreover, electrochemical impedance spectroscopy measurements showed that increasing the number of ARB cycles offers better conditions for forming the passive films.

Deformation textures of aluminum in a multilayered Ti/Al/Nb composite severely deformed by accumulative roll bonding

The accumulative roll bonding process was carried out to produce multilayered Ti/Al/Nb composites up to four cycles. Scanning electron microscopy, transmission electron microscopy electron backscattered diffraction and nanoindentation were employed to investigate the microstructural and texture evolution. A homogenous distribution of Ti/Nb necking layers in Al matrix was achieved after four ARB cycles. Grain refinement was observed to increase with increasing number of ARB cycles. The fraction of high-angle grain boundaries as also increased. Strong recrystallization texture appeared for high number of ARB cycles due to the adiabatic heat that occurs during ARB processing. The shear band at the Ti/Al interface reduced the intensity of the cold rolling fiber textures of Al. There was no evidence of shear component from the orientation distribution function results.