Cycles Of Accumulative Roll Bonding Process Research Articles

Microstructure analysis and observation of peculiar mechanical properties of Al/Cu/Zn/Ni multi-layered composite produced by Accumulative-Roll-Bonding (ARB)

Abstract In the present study, the microstructure and tensile properties of a Al/Cu/Zn/Ni multi-layered composite after various accumulative roll bonding (ARB) passes were evaluated. The results showed that during the early steps of the ARB process, the Ni layer was undergone fracture as the first material. By increasing the ARB cycles to the third one, besides the Ni layer, the Cu layer was also gone through fracture. In contrast, in the Zn layer, only a severely localized necking was seen. Eventually, by the fifth cycle of ARB process a uniform distribution of Ni, Cu and Zn was created within the Al matrix. As well, from the second cycle onwards, CuZn5 intermetallic compound was formed in the Cu and Zn interface because of the stress that induced by rolling process. By increasing the number of ARB cycles to the third one, the elongation of composite improved. Even though the elongation decreases at higher number of passes; however, it is higher than initial passes.

Microstructure and mechanical properties of ultra-lightweight Mg-Li-Al/Al-Li composite produced by accumulative roll bonding at ambient temperature

Microstructural evolution and mechanical properties of ultra-lightweight Mg-14 wt% Li-1wt.% Al/Al-2wt.% Li composite produced by accumulative roll bonding (ARB) at ambient temperature were investigated. The computational simulation revealed the complicated stress and strain distribution in Mg-Li-Al and Al-Li layers during ARB process. The compositions of Al and Mg elements across the interface between Mg-Li-Al and Al-Li layers were increasingly homogeneous with the increase of ARB cycles due to the atomic inter-diffusion, indicating that the bonding between Mg-Li-Al and Al-Li layers was gradually improved. The grain sizes of Mg-Li-Al and Al-Li layers were decreased to about 300 nm and 200 nm after 4 cycles of ARB process, respectively. The brittle intermetallic compounds of Al3Mg2 and Al12Mg17 were gradually formed with the increase of ARB cycles. The microhardness and strength of Mg-Li-Al/Al-Li composite continuously increased, however, the ductility first decreased and then increased with the increase of ARB cycles. The tensile properties, with the ultimate tensile strength (UTS) of 308 MPa and the elongation (EL) of 17.4%, were achieved after 4-cycle ARB process.

High-strength, ductility and modulus Al–Li/B4C composite with near nanostructure produced by accumulative roll bonding

Abstract Al–Li/B4C composite was produced by accumulative roll bonding (ARB) at ambient temperature. The agglomeration of B4C particles in the interfaces between Al–Li layers was evolved to the small clusters and uniform dispersoid particles in the matrix. Quite a few nano-grains were observed in the 8-cycles ARB processed Al–Li/B4C composite, indicating the successful preparation of near nanostructure. The strength and ductility were simultaneously improved with the increase of ARB cycles. The excellent mechanical properties (UTS = 384 MPa, YS = 264 MPa and EL = 10.7%) and high Young’s modulus (87 GPa) were achieved after 8 cycles of ARB process. The high strength of 8-cycle ARB processed Al/B4C composite was related to grain refinement strengthening and dislocation strengthening. The pleasurable ductility of 8-cycle ARB processed Al–Li/B4C composite was attributed to the uniform distribution of B4C particles and proper wide grain size distribution.

A substantial improvement of tensile properties through microstructure engineering in a high Ni-0.2C TRIP steel under severe plastic deformation

In the present paper, microstructural evolution and mechanical properties changes of an ultrafine-grains (UFGs) Fe-24Ni-0.2C steel processed via accumulative roll bonding (ARB) is investigated. Characterization of microstructure with Electron Backscatter Diffraction (EBSD) technique revealed that a substantial grain refinement happened after 6-cycle ARB process. As well, elongated UFGs austenite with mean grain size smaller than 200 nm was obtained in such a condition. Furthermore, phase analysis map acquired from EBSD technique revealed that the microstructure of the starting sheet contained martensite (>30%) which transformed to austenite after 6 cycles of ARB process. Such a phenomenon indicated that, through grain refinement, austenite stabilization is attainable with the ARB process. It was also found that yield/tensile strengths, as well as toughness of the ARB processed specimens are enhanced, particularly when the ARB cycle is increased. Finally, it was established that deformation-induced martensite transformation provides extra strain hardening capability ensuing a substantial enhancement of uniform elongation and toughness in the UFGs metastable austenitic steel. This UFGs steel showed considerable uniform elongation and ultrahigh strength at 6-cylce ARB process.

Electrochemical performance of Pb[sbnd]Co composite anode during Zinc electrowinning

In this study, the electrochemical and anodic behaviors of CoPb anodes in electrowinning process were investigated. Accumulative roll bonding (ARB) method was applied to fabricate CoPb composites. The electrochemical properties of the produced anodes were investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry technique (CV), electrowinning tests, and scanning electron microscopy (SEM). The results indicated that ARB-process is an appropriate method to developed CoPb anodes. The produced anodes containing 0.5% of Cobalt particles as a second phase after 10 cycles of ARB process which is named Pb-0.5%Co-10pass samples showed 83.37% increase in current density compared to pure lead anode. The results of electrowinning tests revealed that Pb-0.5%Co-10pass samples had the best anodic performance with a significant lower corrosion rate, product and electrolyte contamination, slime formation, energy consumption and a higher Zn deposit as a product and energy conservation.

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.

Mechanical and microstructural investigation of Zn/Sn multilayered composites fabricated by accumulative roll bonding (ARB) process

In the present research, Zn/Sn composites were produced for the first time by accumulative roll bonding (ARB) process up to seven cycles. The microstructure evolution was evaluated by scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and the mechanical properties of Zn/Sn multilayered composites were measured by Vickers microhardness and tensile tests at different cycles of ARB process. It was observed that by increasing the ARB cycles, due to the differences in the mechanical behavior of the layers, Zn layers were necked at first, fractured and dispersed between Sn layers. After seven ARB cycles, a laminated composite with wavy interfaces and homogeneously distributed lenticular fragments of Zn was achieved. The XRD results showed that no new phase has been formed during the ARB process. Fracture surfaces of the samples after tensile tests were observed by SEM. Fracture surfaces revealed that fracture mode for the Zn layers was brittle at all cycles and fracture mode for the Sn layers was ductile at initial cycles and then changed to shear ductile fracture by increasing the ARB cycles.

A comprehensive study of microstructure development and its corresponding tensile properties in nano/ultrafine-grained metastable austenitic steel during accumulative roll bonding (ARB)

The evolution of microstructure together with mechanical properties change of Fe-28.5Ni steel, used in design of marine and nuclear related products, processed by different deformation amount during ARB process was elaborated by Electron Backscattered Diffraction (EBSD) method. EBSD results showed that the initial structure of the material contained retained austenite as the main phase besides martensite phase. Martensite phase was diminished after successive ARB cycles due to reduction of martensite start (Ms) temperature. EBSD microstructural results exhibited that a stabilized nano structure was attained by 6-cycle or 8-cycle of the ARB process with the latter having slightly higher grain size due to the grain growth effect of dynamic restoration mechanism resulting from extreme deformation. Tensile test data on different cycles of ARB processed specimens showed that yield and ultimate tensile strengths were substantially increased after the first cycle of the ARB coinciding with the substantial amount of dislocations in the form of low angle grain boundaries (LAGB). Strengths increased in the successive cycles, though in a much slower pace. Ultra-fine grains were formed instead after high cycles of ARB process. Although such increase in strength generally came at the expense of ductility, the material after 8-cycle had still substantial ductility.

Microstructural characteristics of nano-structured Fe-28.5Ni steel by means of severe plastic deformation

Microstructural evolution together with changes in mechanical properties of an high nickel content steel processed by various cycles of accumulative roll bonding (ARB) is explored. It is shown by Electron Backscatter Diffraction (EBSD) analysis that after successive roll bonding processes a stabilized nano-structure is developed containing sufficient amount of ductility under severe plastic deformation. A mean grain size of few hundred nano meter was obtained after 6-cycle of ARB process meaning that the successive ARB cycles made the structure quite refined. The starting material was mainly coming from the transformation of martensite to retained austenite, particularly under high temperature and in high cycle of ARB process. This is an early indication of the stabilization of retained austenite during the ARB process through grain refinement phenomenon. Uniaxial tensile test demonstrated that yield strength significantly improves by only one cycle of ARB process. Successive cycles of ARB process gradually increased the yield and the ultimate tensile strengths at the expense of ductility. The main cause of such a substantial increase in yield strength is discussed. Remarkably high amount of ductility was still observed in a very high amount of deformation that was applied in the 6-cycle ARB process.

Towards engineering of mechanical properties through stabilization of austenite in ultrafine grained martensite–austenite dual phase steel processed by accumulative roll bonding

In this study, microstructure development with respect to mechanical properties in ultrafine grained dual phase (martensite/austenite) by chemical composition of Fe-24Ni-0.1C (wt%) steel processed by 1-cycle and 6-cycle of accumulative roll bonding (ARB) process was investigated. Microstructure characterization by electron backscatter diffraction (EBSD) system showed that significant grain refinement occurred after 6 cycles ARB process and an average grain size smaller than 200nm was obtained. Moreover, phase analysis map obtained from EBSD system showed that the microstructure of starting material is mostly constituted of martensite phase (more than 70%) and transforms to retained austenite by 6 cycles of ARB process. This phenomenon has proved that retained austenite is stabilized during the ARB process through grain refinement. Uniaxial tensile tests exhibited that yield strength did not significantly improve by 1-cycle reverse transformation compared to the starting material. In contrast, further continuation of the ARB process caused gradual increase in yield and ultimate tensile strengths. The significant improvement in yield strength should be originated from significant grain regiment introduced by 6 cycles of the ARB process. Surprisingly, the uniform tensile elongation for the starting material and the 6 cycles ARB processed specimen are almost the same, though yield and ultimate tensile strengths are considerably improved by employing 6 cycles of ARB process.

Evaluation of Mechanical Properties and Structure of Al-1100 Composite Reinforced with ZrO2 Nanoparticles via Accumulative Roll-Bonding

In this study, aluminum metal matrix composites reinforced with ZrO2 nano-particles in volume fraction of 0.5, 0.75 and 1 % were manufactured through accumulative roll bonding (ARB) process. The results of composite microstructure indicated excellent ZrO2 particle distribution in the Al matrix after 10 cycles of ARB process. The X-ray diffraction results also showed that nanostructured Al/ZrO2 nano-particles composite with the average crystallite size of 48.6 nm was successfully achieved after 10 cycles of ARB process. The tensile tests were conducted on the ARBed strips. The tensile strength increased 2.15 times more than the initial value. The elongation dropped abruptly at the first cycle, and then increased slightly. The SEM images observations from the fracture surface showed that after 10 cycles of ARB process the fracture was almost shear fracture mode with fine and stretched pores.

Strengthening mechanisms in nanostructured interstitial free steel deformed to high strain

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

Fabrication of Al/Al2O3/TiC hybrid composite by anodizing and accumulative roll bonding processes and investigation of its microstructure and mechanical properties

In the present study, Al/Al2O3/TiC hybrid composite was produced using anodized strips and accumulative roll bonding (ARB) process. Alumina layers with various thicknesses were firstly obtained by anodizing the aluminum strips at different times. The anodized strips were then used along with certain amount of TiC particles (1vol%) as dispersed layer in order to fabricate Al/Al2O3/TiC hybrid composite. The resulting microstructures as well as the corresponding mechanical properties of the composites in different cycles of ARB process were studied. It was found that after one ARB cycle, departing and fracturing phenomena occurred in brittle alumina layer, followed by breaking down the alumina fragments to finer particles as the number of rolling cycles increased. In addition, by applying eight ARB cycles, the distribution of reinforcement particles (Al2O3, TiC) in aluminum matrix became highly uniform. It was shown that the mechanical properties of the hybrid composite such as tensile strength and elongation were enhanced as the number of ARB cycles increased. The results also showed that adding of up to 1.6vol% alumina in aluminum matrix enhanced considerably the yield and tensile strength of hybrid composite, whereas increasing the amount of alumina to 2.1vol% deteriorated the tensile properties. Finally, the fracture surfaces of the samples after the tensile tests showed that the fracture mode of composite was shear ductile rupture.

Enhancement of Low Temperature Toughness in Bulk Nanostructured Metals

Brittle-to-ductile transitions (BDT) in fine-grained Ti added ultra-low carbon steels were investigated. Temperature dependences of impact absorbed energy were measured using specimens with grain sizes of 0.4, 2, 9 and 70µm of which the grain sizes were controlled by heat treatments after five cycles of accumulative roll-bonding process. Although the BDT temperatures were decreased with the decrease in the grain size, the shape of BDTcurves in fine-grained steels are different from those of coarse grains. Specimens with coarse grains show abrupt increase in the absorbed energy at the BDT temperature while fine-grained steels exhibit slight jump of absorbed energy at the BDT temperature and then the energy gradually increases with temperature, showing the enhancement of toughness at low temperatures in fine-grained steels. In the present paper, the characteristic BDT in fine-grained steels was discussed in terms of the thermally activated process of dislocation glide. [doi:10.2320/matertrans.MH201319]

Study on the microstructure and mechanical properties of multilayer Cu/Ni composite processed by accumulative roll bonding

In the present research, Cu/Ni multilayer composite was produced by accumulative roll bonding (ARB) process. The microstructure evolution and mechanical properties of the multilayered Cu/Ni composites were evaluated within different cycles of ARB process. It was observed that as the number of ARB cycles increased, the thickness of Ni layers was decreased and synchronous necking and fracturing occurred. After six ARB cycles, a multilayer Cu/Ni composite with homogeneously distributed fragmented nickel layers in Cu matrix was achieved. It was found that with increasing strain during ARB cycles strength and elongation of these composites increased. The observations of fracture surfaces after tensile tests revealed that rupture mode of Cu/Ni multilayer composites is ductile rupture with shear dimples.

Fabrication of Al/Ni/Cu composite by accumulative roll bonding and electroplating processes and investigation of its microstructure and mechanical properties

Al–Ni–Cu composite was produced using accumulative roll bonding (ARB) and electroplating processes. Nickel was electroplated on copper substrate for a certain time and voltage. In this study, the microstructural evolution and mechanical properties of the Al–Ni–Cu composite during various ARB cycles were studied by optical and scanning electron microscopes, microhardness, tensile and bending tests. It was observed that at first, nickel layers and then copper layers, were necked, fractured and distributed in aluminum matrix as accumulative roll bonding cycles were increased. Finally, after 11 cycles of ARB process, a completely uniform composite was produced with a homogeneous distribution of copper and nickel particles in aluminum matrix. The results showed that by increasing the number of ARB cycles, the bending strength of produced composite was increased. Also, it was found that when the number of cycles was increased, not only elongation was increased but also the tensile strength of the composite was improved. Microhardness for different elements in different cycles was also evaluated. Finally, fracture surfaces of samples were studied, using scanning electron microscopy (SEM), to reveal the failure mechanism.

Investigation of Microstructure of the Commercial Pure Aluminium in the ARB Process

The severe plastic deformation (SPD) of metallic materials has become attractive in recent years. Accumulative roll bonding (ARB) is a SPD process that can impose deformation to a sheet metal, as it develops fine grains of typically submicrometer or even the nanometer level in polycrystalline materials. The purpose of the present study is investigation of microstructural evolution and micro hardness behavior of the commercial purity Aluminium (AA1050) severely deformed by the ARB process. The microstructural evolution during 13 cycles of ARB process was investigated. With increasing ARB cycles the grains size reduced in nanometer range. Furthermore, Micro-Vickers hardness measurement was carried out throughout thickness of the ARB processed sheets.

Investigation on microstructure and mechanical properties of Al–Zn composite during accumulative roll bonding (ARB) process

Abstract In this study, Al–Zn composite was produced for the first time by using of Al 1050 and commercial Zn alloy sheets through accumulative roll bonding (ARB) process at ambient temperature. In this process after sandwich preparation, in per cycle applied 50% reduction in thickness. It was observed that by increasing ARB cycles, thickness of individual Al and Zn sheets decreased; finally, zinc layers were necked, fractured and dispersed in the aluminum matrix. After ten ARB passes, an Al–Zn composite with homogeneously distribution of fragmented zinc layers with thickness of less than 3 μm in aluminum matrix was produced. Structure and mechanical properties of this composite were evaluated at different cycles of ARB process. During ARB cycles, it was observed that with increase of number of ARB cycles, the strength and microhardness increased while elongation at the first cycles increased and then decreased.

Evaluation of Texture and Grain Size of Nanograined Copper Produced by the Accumulative Roll Bonding Process

Pure copper was intensely deformed by accumulative roll bonding (ARB) for up to eight cycles at ambient temperature. X-ray diffraction (XRD) was used to evaluate the grain size and texture during the ARB process. The Williamson–Hall method was used to calculate the grain size from the XRD patterns, which was about 30 nm after eight cycles of the ARB process. Texture analysis revealed cube texture in the initial copper. The intensity of cube texture decreased after one cycle of the ARB process. The texture of two-cycle ARB-processed sample was a transition texture, from cube to shear texture (rotated cube) that appeared after two cycles of ARB process in the subsurface regions. This shear texture developed due to shear deformation induced by the high level of friction between the rolls and the sheet. Moreover, shear texture was replaced by recrystallization texture (cube component) by annealing the ARB-processed samples. This result was caused by preferential growth of cube grains.

High-strength, high-conductivity ultra-fine grains commercial pure copper produced by ARB process

Accumulative roll-bonding process is a severe plastic deformation process capable of developing grains below 1 μm in diameter. In this study, microstructure, mechanical properties and electrical conductivity of commercial pure copper strips processed by accumulative roll-bonding were investigated. Transmission electron microscopic micrographs of the strips produced by eight cycles of accumulative roll-bonding process showed ultra-fine grains ∼180 nm in size with high angle grain boundaries. Also tensile strength and microhardness of the accumulative roll-bonding processed samples increased with increasing the number of accumulative roll-bonding cycles. Whereas, the elongation dropped abruptly at the first cycles, above which it increased slightly. The electrical conductivity decreased with increasing accumulative roll-bonding cycles up to 6 cycles and then increased up to 8 cycles of accumulative roll-bonding process.