Accumulative Roll Bonding Cycles Research Articles

Superior Mechanical Properties of Aluminum–Titanium Laminates in Terms of Local Hardness and Strength

Accumulative roll bonding (ARB) is a very useful method to produce ultrafine‐grained (UFG) sheet material with extraordinary mechanical properties. Besides the production of UFG mono‐materials, it is possible to create tailored multicomponent materials by stacking different materials. In this work, the aluminum alloy AA2024 and titanium grade1 are roll‐bonded in order to achieve laminated metal composites (LMC) with an UFG microstructure. The mechanical properties and microstructural evolution during the ARB process of the LMC are analyzed and compared to that of LMCs. The mono‐materials show an ultrafine grain structure after at least three ARB cycles which results in an increased yield and ultimate tensile strength. Most interestingly, the produced LMCs exhibit mechanical properties which are way better than the properties of the UFG mono‐materials, when a linear rule of mixture is applied. The strength of the titanium–aluminum laminate is very close to the strength of the UFG titanium. Although, the density is significantly lower. The light‐weight potential of the LMC is best expressed by the specific strength. Compared to the specific strength of UFG mono‐material titanium of about 168 Nm g−1 and UFG mono‐material aluminum of about 195 Nm g−1 the ARB laminate exhibits the highest specific strength of about 217 Nm g−1 after three cycles.

Microstructure, Texture, and Mechanical Properties of Ni-W Alloy After Accumulative Roll Bonding

In this study, the microstructure, texture, and mechanical properties evolution of Ni-14W (wt.%) alloy processed up to four cycles of accumulative roll-bonding (ARB) were investigated using electron backscatter diffraction, microhardness measurements, and tensile tests. The initial equiaxed grains, with an average size of 10 μm, underwent a strong refinement after ARB processing. The elongated ultrafine grains were parallel to the rolling direction, with a grain thickness of 0.2 µm. The texture after ARB processing was characterized by the typical rolling components (Copper, S and Brass), which showed a tendency toward stabilization after four cycles. The microhardness increased substantially (+ 86%) and seemed to saturate after three cycles. The tensile tests demonstrated that Ni-14W samples subjected to ARB processing exhibited high strength (> 1200 MPa after three ARB cycles) and very poor ductility.

Nanostructured AA5005/Al2O3 composite manufactured by anodising and accumulative roll bonding

ABSTRACTIn this study, nanostructured AA5005/6 vol.-% Al2O3 composite manufactured by anodising and accumulative roll bonding (ARB) processes was investigated. The microstructure of the AA5005/Al2O3 composite after ninth ARB cycle exhibited a good distribution of alumina reinforcement particles in the AA5005 matrix. It was found that with increasing the number of cycles, the tensile strength of the monolithic and composite samples increased, but their ductility decreased at the first ARB cycle and then increased. The mean grain size of the composite sample after the ninth cycle was 88 nm. The tensile strength of the composite was 3.3 times higher than the initial AA5005 sheet. Observations revealed that the failure mode in the AA5005/Al2O3 composite was the shear ductile fracture.

An Experimental Study of Fracture Toughness for Nano/Ultrafine Grained Al5052/Cu Multilayered Composite Processed by Accumulative Roll Bonding

In this study, ultrafine grained Al5052/Cu multilayered composite has been produced by accumulative roll bonding (ARB) and fracture properties have been studied using plane stress fracture toughness. The fracture toughness has been investigated for the unprocessed specimens, primary sandwich and first, second, and third cycles of ARB process by ASTM E561 and compact tension (CT) specimens. Also, the microstructure and mechanical properties have been investigated using optical microscopy, scanning electron microscopy, uniaxial tensile tests, and microhardness measurements. The value of plane stress fracture toughness for the ultrafine grained Al5052/Cu composite increased by increasing the number of ARB cycles, continuously from the primary sandwich to end of the third cycle. The maximum value of 59.1 MPa m1/2 has been obtained that it is about 2.77 and 4.05 more than Al5052 and pure Cu (unprocessed specimens). This phenomenon indicated that ARB process and the addition of copper to aluminum alloy could increase the value of fracture toughness to more than three times. The results showed that by increasing the ARB cycles, the thickness of copper layers reduced and after the fifth cycle, the excellent uniformity of Cu layers achieved. By increasing the number of ARB cycles, the microhardness of both aluminum and copper layers have been significantly increased. The tensile strength of the sandwich has been enhanced continually, and the maximum value of 566.5 MPa has been achieved.

The effect of severe plastic deformation and annealing conditions on mechanical properties and restoration phenomena in an ultrafine-grains Fe-28.5%Ni steel

ABSTRACTThe effect of annealing condition on the microstructure evolution, together with mechanical properties of Fe-28.5Ni steel processed by one and six cycles of accumulative roll bonding (ARB), was explored. The evolution of microstructure was studied by means of Electron Backscattered Diffraction method. The ARB-processed specimens were annealed for 30 minutes between 500°C and 600°C, and the effect of these annealing processes was elaborated. Results showed a significantly reduced martensite phase during ARB process cycles. Moreover, a refined and stabilised ultrafine structure was obtained in 6-cycle ARB-processed specimen. Results also show that by annealing the 1-cycle specimen at 550°C, no significant microstructural change and mechanical properties variation are identified. As such, no significant microstructural change and mechanical properties variation were notified for annealing of 6-cycle ARB-processed specimen at 500°C. However, annealing at 600°C in both conditions led to a complete recrystallisation of the deformed structure. Annealing at 550°C in 6-cycle ARB-processed specimen showed partial recrystallisation as well as an abnormal grain growth characteristic. The abnormal grain growth was seen by annealing of 1-cycle ARB-processed specimen at 600°C. The changing features of dislocations were discussed in these specimens in terms of changing the dynamics of low- and high-angle grain boundaries. Tensile test results also showed a significant increase in the yield/ultimate tensile strengths with the application of ARB cycles. Although ARB process led to a rapid reduction of total elongation, full restoration during high-temperature annealing returned this value back to the initial, non-deformed, condition.

Evaluation of Microstructure and Mechanical Properties of Multilayer Al5052–Cu Composite Produced by Accmulative Roll Bonding

A multilayer Al5052–Cu composite is prepared by accumulative roll bonding (ARB) and the microstructure and mechanical properties are evaluated using optical microscopy, scanning electron microscopy (SEM), tensile tests, and micro-hardness measurements. The results show that the thickness (1000 μm) of copper layers of the initial sample is reduced to ~7 μm after the fifth ARB cycle, while the thickness of Al layer increases. With increasing number of ARB cycles, the microhardness of both aluminum and copper layers is significantly increased. The tensile strength of the sandwich is enhanced continiousely, and the maximum value of 566.5 MPa is achieved. The high strength of 566.5 MPa and ductility of 9.61% is achieved, which is ~47 and ~21% higher, than the maximum values found out in the publications. The investigation of the tensile fracture of surfaces during ARB indicates that the increase in ARB cycles changes the fracture mechanism to shear ductile.

Grain and texture evolution in nano/ultrafine-grained bimetallic Al/Ni composite during accumulative roll bonding

The evolution of grain structure during plastic deformation has a significant effect on texture variations and, in turn, the material properties. However, the metal physics leading to a stationary grain size regime in rolled Al combined with a harder phase remains poorly understood. Therefore, the grain and texture evolution in the Al phase and the possible grain coarsening mechanisms operating during accumulative roll bonding (ARB) were investigated in this work. Three ARB cycles were performed at room temperature with the aim of obtaining a bimetallic Al–Ni composite. The microstructure and texture evolutions in this composite were characterized via field emission gun scanning electron microscopy combined with electron backscatter diffraction. With increasing strain, the lamellar grain structure of Al developed into a semi-equiaxed grain structure. Correspondingly, the grain length and thickness decreased from 672 to 0.84 µm and 24.8 to 0.60 µm, respectively. Grain fragmentation was, however, most efficient in the initial stages of rolling, since continuous dynamic recrystallization prevented further grain refinement especially in the last cycle. Consequently, after a strain of 2.7, the refinement continued at decreasing rates, yielding a fragmentation ratio of one at a lower strain than that reported for single-phase Al composites. The mid-section layers of the Al phase were characterized by a mixture of shear and plane strain compression textures. After the third ARB cycle, the Al phase was characterized by a near random texture resulting from grain fragmentation. This fragmentation was induced by local plastic flow in the Al phase, owing to the presence of hard Ni fragments.

Relationship between initial hydrogen absorption properties and microstructures of Mg/Cu super-laminate composites with different accumulative roll bonding cycles

The relationship between initial hydrogen absorption properties and microstructures of Mg/Cu super-laminate composites (SLCs) with different accumulative roll bonding (ARB) cycles was investigated. Hydrogenation of Mg was dominant in Mg/Cu SLCs with 5 and 10 cycles of ARB, whereas that of Mg2Cu was dominant in Mg/Cu SLCs with 20 and 30 cycles of ARB. The growth rate constants did not show a significant difference among Mg/Cu SLCs with different ARB cycles. It is considered that the average thickness of Mg + Cu layers in as-rolled Mg/Cu SLCs as a function of ARB cycles has a large influence on initial hydrogenation properties and microstructure formation processes.

Development and characterization of Al/MWCNT–Al2O3 hybrid composite by accumulative roll bonding

A high-strength hybrid composite was produced by eco-friendly accumulative roll bonding (ARB) process. Multiwall carbon nanotubes and alumina layers as reinforcements were embedded in a matrix of aluminum 1100. The produced hybrid composite was evaluated for structural changes and mechanical properties. The structural micrographs showed that by increasing the rolling cycles, a more uniform distribution of the reinforcements is obtained. After ten cycles of ARB, the composite material reached strength of about 300% higher than that of the annealed aluminum 1100. The elongation of the composite material is decreased by adding reinforcements. However, at a constant value of reinforcements, the elongation slowly increased during sequential rollings. A shear ductile rupture type failure was responsible for fracture of tensile test specimens of both composite and monolithic specimens.

Microstructure and mechanical properties of Al/Cu/Mg laminated composite sheets produced by the ARB proces

In the present study, an Al/Cu/Mg multi-layered composite was produced by accumulative roll bonding (ARB) through seven passes, and its microstructure and mechanical properties were evaluated. The microstructure investigations show that plastic instability occurred in both the copper and magnesium reinforcements in the primary sandwich. In addition, a composite with a perfectly uniform distribution of copper and magnesium reinforcing layers was produced during the last pass. By increasing the number of ARB cycles, the microhardness of the layers including aluminum, copper, and magnesium was significantly increased. The ultimate tensile strength of the sandwich was enhanced continually and reached a maximum value of 355.5 MPa. This strength value was about 3.2, 2, and 2.1 times higher than the initial strength values for the aluminum, copper, and magnesium sheets, respectively. Investigation of tensile fracture surfaces during the ARB process indicated that the fracture mechanism changed to shear ductile at the seventh pass.

Microstructure, texture and mechanical properties of AA 1060 aluminum alloy processed by cryogenic accumulative roll bonding

AA 1060 aluminum alloy sheet was processed to five accumulative roll bonding (ARB) cycles at cryogenic temperature. The microstructure, texture and mechanical properties of the ARB processed sheets were investigated. The results show that the surface layer of the ARB processed sheets exhibits a significant r-cube shear texture. Initial cube orientation at the surface layer was gradually rotated to the r-cube orientation during the ARB process, leading to the increase in the strength of the r-cube shear texture with ARB cycles. The texture evolution at the surface layer was quantified in terms of a simple relation between the texture volume fractions and accumulated true strain. The strength of the β fiber rolling texture and the distribution of orientation intensities along the β fiber at the center layer were strongly affected by the initial texture. As the ARB cycles increased, the initial texture was changed from the cube texture to the r-cube texture, leading to a continuous increase in the strength of the β fiber rolling texture dominated by the C orientation. The yield and ultimate tensile strength of the ARB processed sheets increased markedly after the first ARB cycle and then increased slowly with increasing ARB cycles, while the elongation decreased accordingly.

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.

Microstructure and mechanical properties of SiC-particle-strengthening tri-metal Al/Cu/Ni composite produced by accumulative roll bonding process

In this study, a multilayer Al/Ni/Cu composite reinforced with SiC particles was produced using an accumulative roll bonding (ARB) process with different cycles. The microstructure and mechanical properties of this composite were investigated using optical and scanning microscopy and hardness and tensile testing. The results show that by increasing the applied strain, the Al/Ni/Cu multilayer composite converted from layer features to near a particle-strengthening characteristic. After the fifth ARB cycle, a composite with a uniform distribution of reinforcements (Cu, Ni, and SiC) was fabricated. The tensile strength of the composite increased from the initial sandwich structure to the first ARB cycle and then decreased from the first to the third ARB cycle. Upon reaching five ARB cycles, the tensile strength of the composite increased again. The variation in the elongation of the composite exhibited a tendency similar to that of its tensile strength. It is observed that with increasing strain, the microhardness values of the Al, Cu, and Ni layers increased, and that the dominant fracture mechanisms of Al and Cu were dimple formation and ductile fracture. In contrast, brittle fracture in specific plains was the main characteristic of Ni fractures.

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.

Investigation on microstructure and mechanical properties of Al/Al-Zn-Mg–Cu laminated composite fabricated by accumulative roll bonding (ARB) process

In this study, an Al/Al-Zn-Mg-Cu laminated composite was successfully produced for the first time by using Al 1050 and a super high strength 7xxx aluminum alloy sheets through accumulative roll bonding (ARB) process at an elevated temperature. In this process after sandwich preparation, in per cycle applied 50% reduction in total thickness. The microstructural investigations after different ARB cycles showed that ARB process led to a fine distribution of the secondary phases and also a relatively remarkable decrease in their particle size in the Al-Zn-Mg-Cu (AZMC) layer. Furthermore, it was observed that all the layers of the ARBed sheets remained relatively straight without any necking or fracture during the plastic deformation in the first two cycles. Also, the macrostructure showed elongated and ultra-fine grains after the fourth cycle in the AZMC and pure Al (PA) layers, respectively. In addition, computer simulation demonstrated strain and stress gradients in the ARBed sheet. The mechanical examinations displayed a significant improvement of elongation and ultimate tensile strength (UTS) values and also microhardness values of the AZMC layer with increasing the ARB cycles. However, the microhardness variations were so slight (< 4%) in the PA layer during the ARB process. Fractographic observations revealed that the fractured surfaces of the PA layers consist of necking as well as dimples and that of the AZMC ones include dimples and partly shear regions after ARB process.

The formability investigation of CNT-reinforced aluminum nano-composite sheets manufactured by accumulative roll bonding

There is an increasing demand for materials with outstanding mechanical properties for many applications. Ultrafine-grained (UFG) materials as a path for improving the base materials and composite materials as a media for combining the superior properties of different materials are the current solutions for the demanded properties. Severe plastic deformation can be used for manufacturing UFG materials with nano-structure. In this research, accumulative roll bonding (ARB), as a severe plastic method, is utilized for manufacturing aluminum matrix composites reinforced with carbon nano-tubes (CNT). An experimental platform is used to investigate the mechanical properties of ARB-ed AA1200 nano-composites with 2, 6, 32, and 128 layers. Tensile deformation via the Lankford parameter is used to study the anisotropy of the samples. It is observed that this parameter is a function of the number of ARB cycles and increases significantly by increasing the ARB cycles. Moreover, the Hollomon analysis is used to investigate the strain-hardening behavior of the samples. The results showed that the strain-hardening exponent of ARB-ed AA1200 sheets reinforced with CNT decreases by increasing the number of ARB cycles. The formability of the ARB-ed AA1200 nano-composite samples is investigated analytically by the Marciniak–Kuczinsky model and experimentally using the Erichsen tests. The results revealed that the tensile properties are enhanced and more homogenous structures are obtained; however, formability is reduced. In order to obviate this issue, annealing the samples for 30 min at 250 °C was adapted. As a result, formability is improved at the cost of a slight reduction in strength. The obtained results can be due to recrystallization and grain growth alongside the dissolving of the brittle intermetallic oxides at the interface of the layers after annealing. Annealing is used as a mediator to reach a balance between strength, ductility, and formability, so an appropriate formability is achieved at the end.

Microstructure and mechanical properties of laminated Al–Cu–Mg composite fabricated by accumulative roll bonding

In the present research, laminated Al–Cu–Mg composite was processed by the accumulative roll bonding (ARB) method. Initially, aluminium, copper and magnesium strips were alternatively stacked together. Then these stacked strips were rolled at $$150^{\circ }\hbox {C}$$ up to five ARB cycles. The microstructure of composites was studied by optical microscopy. Micro-hardness and tensile tests were conducted to evaluate mechanical properties of the processed composites. After the first cycle of ARB, it was observed that copper and magnesium layers were necked and fractured. With increasing ARB up to four cycles, laminated Al–Mg–Cu composite with homogeneous distribution of fragmented reinforcement in matrix was produced. It was observed that with increasing ARB up to four cycles the strength and micro-hardness of fabricated composites increased and elongation decreased at the same time. These differences in mechanical behaviour have been attributed to the microstructural aspects of the individual layers and the fragmentation processes.

Development of Cu-matrix, Al/Mn-reinforced, multilayered composites by accumulative roll bonding (ARB)

In this work, nanostructured Cu/Al/Mn multilayered composites were successfully fabricated by the accumulative roll bonding (ARB) method. The microstructure of the produced composites was studied by X-ray diffraction and scanning electron microscopy. Also, the hardness, tensile and corrosion behaviors of the composites were studied as a function of ARB cycles. It was observed that by increasing the number of ARB cycles, the thickness of the Al layers is decreased from 0.3 mm to 0.25 μm, where a Cu-matrix, Al/Mn-reinforced, multilayered composite with homogeneously distributed Al layers and Mn particles was achieved after nine ARB cycles. Also, the results revealed the development of nanostructures with the mean crystallite size of about 50 nm in the produced composites. According to the tensile experiments, by increasing ARB cycles, the strength of the composites was increased and reached 420.8 MPa. The electrochemical corrosion behavior of the produced composites was also investigated in a 3.5 wt % NaCl solution by a potentiostat-galvanostat device. It was found that the corrosion rate of the composite is increased by increasing ARB cycles from 5 μA/cm2 to 12.2 μA/cm2 and then decreased to 9.5 μA/cm2.

Static recrystallization and grain growth of accumulative roll bonded aluminum laminates

Abstract

Experimental evaluation of the plane stress fracture toughness for ultra-fine grained aluminum specimens prepared by accumulative roll bonding process

In this research, the plane stress fracture toughness of ultra-fine grained aluminum specimens produced through accumulative roll bonding (ARB) process was investigated for the first time. The specimens were produced successfully by the ARB process up to 7 cycles with the amount of 50% thickness reduction in each cycle at room temperature without using lubricant. The fracture toughness was evaluated for the annealed and different ARB cycles using ASTM E561 standard and compact tension specimens. Additionally, mechanical properties, tensile fracture surfaces and crystallite size of ultra-fine grained aluminum ARBed specimens were evaluated by uniaxial tensile tests, microhardness measurements, scanning electron microscopy and X-ray diffraction. By increasing the number of the ARB cycles, fracture toughness was increased and the maximum value of this parameter was achieved in the last cycle, which was approximately 25.4 MPam1/2 that it increased by 155% higher than the annealed specimen. Results of X-ray diffraction demonstrated that by increasing the number of the ARB cycles, crystallite size decreased so that it reached 175nm for the 7th cycle ARBed specimen from 1341nm for annealed samples. Furthermore, by increasing the number of the ARB cycles up to the 7th cycle, tensile strength and microhardness of ultra-fine grained aluminum increased to 232MPa and 51VHN, respectively. At first, the value of elongation decreased and then increased. The SEM results showed that ductile fracture mode with large dimples occurring in the annealed specimen, changed to shear ductile fracture with elongated sophomoric shear and fine dimples after the ARB process.