Abstract Accumulative Roll Bonding Research Articles

Bonding of similar AA3105 aluminum alloy by Accumulative Roll Bonding process

Accumulative roll-bonding (ARB) is a novel plastic straining process aimed at bonding of similar and dissimilar metal combinations. Moreover, it is used recently to produce ultrafine grain materials and metal matrix reinforced composites to enhance mechanical, electrical, and corrosion resistance properties. This work presents an experimental study of roll bonding and accumulative roll bonding of similar AA3105 aluminum alloy at 300°C with a final thickness of 1.2 mm, focusing especially on bond strength evaluation and layers continuities. Tensile tests and three-points bending were performed to mechanical characterize the produced sheets in the various steps and based on the number of the cycles. The maximum strength was reached after 3 ARB cycles. After 4 cycles, the bonding interfaces have a uniform distribution through the sheet thickness, it is possible to distinguish only the interface formed in the last pass in the fracture surface, and no significant enhancement in strength was observed. Starting from 2 ARB cycles, micro-cracks were observed at the outer surface for bending angles greater than 90 deg, and at 180 deg all ARBed samples except A1 were failed.

Review on Accumulative Roll Bonding (ARB) Techniques for Improving the Mechanical Properties of Multi-Layered Materials

Accumulative Roll Bonding (ARB) is one among the techniques in Severe Plastic Deformation (SPD) which is used to produce ultrafine grains and nanocrystalline structure in the materials used. Tensile test, micro hardness test, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and bending tests are the various tests carried out to understand the grain refinement of ARB materials. ARB is carried out in homogenous and heterogeneous materials to bring out the useful applications of ultrafine grained materials. ARB process mainly carried out in room, warm and hot temperature. The variations in the structure of the material are obtained by changing the load applied on the roller and by increasing the number of passes. This review paper brings out how the mechanical properties of the materials are improved by ARB process

Microstructure of AA7075 Based Composite by Accumulative Roll Bonding Process

Accumulative Roll Bonding (ARB) is a Severe Plastic Deformation (SPD) process invented in order to fabricate ultrafine grained materials. Aluminum Alloy series 7075 (AA7075) is a metal as a matrix reinforced by Alumina Nanofiber (ANF). In the development of advanced materials, AA7075/ANF composite metal is very suitable if it is processed by ARB, due to the combination of high style roll that is capable of producing material properties better. Hardness of AA77075 without reinforcement reached 128.3 Hv10. The additions of ANF on AA7075 reduce the hardness of 103.2 Hv10. This is due to large deformation of high load on the ARB which results in decrease levels of precipitates as well as lower density and reduction in the average grain size.

Microstructure and mechanical properties of ultrafine grained complex copper alloy fabricated by accumulative roll-bonding process.

Accumulative roll-bonding (ARB) process using dissimilar copper alloys was performed up to six cycles (-an equivalent strain of 4.8) at ambient temperature without lubricant for fabrication of a new complex copper alloy. The dissimilar copper alloy sheets of oxygen free copper (OFC) and dioxide low-phosphorous copper (DLPC) with thickness of 1 mm were degreased and wire-brushed for the ARB process. The sheets were then stacked together and rolled by 50% reduction so that the thickness became 1 mm again. The sheet was then cut to the two pieces of same length and the same procedure was repeated up to six cycles. A new sound complex copper alloy sheet in which OFC and DLPC are combined each other was successfully fabricated by the ARB process. The tensile strength of the copper alloy increased with increasing the number of ARB cycles, reached 492 MPa after six cycles, which is about three times of the initial material. The average grain size was 12.6 μm after the 1st cycle, but it became 1.5 μm after six cycles. Microstructures and mechanical properties of the complex copper alloy fabricated by the ARB were investigated in detail.

Modelling Aspects in Accumulative Roll Bonding Process by Explicit Finite Element Analysis

Accumulative Roll-Bonding (ARB) process is a severe plastic deformation (SPD) process, capable of developing grains below 1 μm in diameter and improving mechanical properties of the material. In this study, the authors compared two different FE-codes with respect of its applicability for numerical analysis of the ARB process. Modelling this process was achieved using the explicit code for Abaqus/CAE both in 2D and 3D. The proposed model was used to assess the impact of ARB cycles on the final material properties. The numerical results in 2D and 3D were compared and contrasted. The research work presented in this paper is focused on the simulation optimization based on CPU time minimization. The numerical simulations were also validated through a comparison with the experimental results.

AN EBSD STUDY ON THE MICROSTRUCTURE AND TEXTURE EVOLUTION OF AZ31 MAGNESIUM ALLOY DURING ACCUMULATIVE ROLL-BONDING

Accumulative roll-bonding(ARB) process is appropriate to manufacture nanocrystalline and ultrafine grained sheets and plates which are most widely used material shapes in the commercial and industrial fields.The ARB process was proved to be very effective in refining grains and enhancing the strength of aluminum,steels and copper.However,the ARB was used only for cubic materials and rarely for hcp structured metal.The information available in the literatures about the microstructure change of magnesium alloys during the ARB process is still very limited.ARB was applied to AZ31 magnesium alloy sheets in the present work.ARB procedures were repeated for up to 5 cycles.Before each ARB cycle,the stacked sheets were heated at 350℃for 5 min in an electrical furnace near the rolling mill.The microstructure and texture evolution of an AZ31 during ARB were characterized by electron backscatter diffraction(EBSD).The results show that ARB is an effective grain refinement method for producing AZ31 sheets with fine grain structure.Significant grain refinement was achieved after 3 ARB cycles with average size of about 2.18μm.Grain refinement almost occured during the first three cycles and the distributions of grain size became more uniform as the cycle number increased.The results confirm the existence of critical ARB cycles to obtain dynamic balance between grain refinement and grain growth during the ARB process.Fraction of high angle grain boundaries increased with the increase of ARB cycles.Continuous dynamic recrystallization (CDRX) including rotation dynamic recrystallization(RDRX) occured during ARB of AZ31 as the grain refinement mechanisms.The dynamic recrystallization of AZ31 was activated and enhanced by the accumulated severe strain and shear strain across sheet thickness during ARB.In addition, large strain rate during ARB also contributed to grain refinement with the increase of Zener-Hollomon parameter.Microtextures of AZ31 tended to decrease and the average Schmid factor increased during the first three ARB cycles due to the sever and complex distrubution of shear strain,rotation dynamic recrystallization and rotating the new grains during ARB.

Development of nanostructure in AZ31 magnesium alloy during accumulative roll bonding process

Accumulative roll bonding (ARB) is one of the effective severe plastic deformation methods for developing very fine grained nanostructures. In the present work, grain refinement and microstructural changes of magnesium AZ31 alloy during ARB process was investigated. Sheet specimens up to 256 cold welded layers (eight ARB cycles) were prepared. Evolution of the microstructure was observed using optical microscopy. It is shown that various mechanisms such as rotational recrystallisation (RRX) and twinning are involved in grain refinement at different passes. Increasing the number of ARB cycles leads to an ultra fine grain (UFG) microstructure (almost 500 nm) surrounded by nanoscale grain zones (almost 120 nm). The microstructural evolution is explained by grain refinement along the deformation bands by means of geometrical recrystallisation, RRX and progressive lattice rotation.

Multilayer composite al99.99/almg3 sheets prepared by accumulative roll bonding

Abstract Accumulative roll bonding (ARB) allows producing ultrafine-grained sheets of high strength and has been successfully used to prepare such materials from aluminium alloys. However, due to intensive work hardening of bond-rolled AlMg3 sheets, significant edge cracking occurred. Cracking was reduced by cladding AlMg3 with aluminium. Lamellar composites were thus prepared. Their structure was studied by electron backscatter diffraction and transmission electron microscopy; hardening was evaluated by microhardness measurements and tensile tests. Composite grain sizes are coarser than in the mono-material sheets. Accordingly, the evolution of strength with ARB-cycling in both materials differs. AlMg3 composite layers exhibit less work hardening than the mono-material; the composite strength is between that of the two mono-material ARB-sheets while the ductility does not differ substantially.

Shearing Behaviour and Texture Evolution in Aluminium Sheet Deformed by Accumulative Roll Bonding

Accumulative Roll Bonding (ARB) is a severe plastic deformation technique for producing ultra-fine grain structures in sheet metal. In this investigation, the through-thickness shear strain distribution during single pass rolling of roll-bonded aluminium sheets was monitored via the deflection of an embedded scratch on the through-thickness, pre-polished surface of the material. It was found that, near the sheet surface and at its mid-thickness, rolling generated severe and moderate shearing, respectively. Such shearing was found to have a strong influence on the microstructure and crystallographic texture of the material, which was eliminated during subsequent rolling cycles. Compared to the core of a given rolled layer, both the microstructure and texture at the interface of the layers was inhomogeneous.

Thermal Stability of Ultrafine Grains in Al-Fe-Mn-Si Foils Prepared by ARB and Subsequent Rolling

Accumulative Roll Bonding (ARB) is a severe plastic deformation process that allows producing ultrafine-grained materials (UFG). UFG sheets exhibit enhanced strength and very fine grain structure. Foils used as fins in heat exchangers have to be very thin but must exhibit high strength combined with relatively high formability. Thus, materials produced using ARB may fulfil the exacting requirements on foil properties for such applications. The thermal stability of Al-Fe- Mn-Si foils produced using ARB and subsequent cold rolling was studied and compared with conventionally cold rolled (CCR) counterparts. The stability was assessed by isothermal annealing in the temperature range from 200 to 450 °C. Electron back scatter diffraction in a scanning electron microscope and transmission electron microscopy examinations of foils microstructure in the deformed and annealed states allowed the monitoring of structural changes. The magnitude of mechanical properties changes due to annealing was evaluated by microhardness measurements. Significant hardness increase was observed after annealing at 200 °C only in the ARB samples and was assigned to an annealing-induced hardening. The CCR foil exhibits higher non-recrystallized fraction and smaller mean lamellae boundary spacing in the temperature interval of 200-250 °C than ARB foils. The annealing at 450 °C results in identical hardness values and fully recrystallized microstructure of all foils, regardless the method used for their manufacturing. However, the ARB samples show higher stability of the refined substructure than their cold rolled counterparts due to continuous recrystallization occurring in the ARB foils.

Nano-Structured High Purity Copper Processed by Accumulative Roll-Bonding

Accumulative roll-bonding (ARB) process was applied to an oxygen free copper for improvement of the mechanical properties via ultra grain refinement to nanometer order level. Two copper sheets 1mm thick, 30mm wide and 300mm long are degreased and wire-brushed for sound bonding. The sheets are then stacked to each other, and cold-roll-bonded by 50% reduction rolling. The sheet is then cut to the two pieces of same length and the same procedure was repeated to the sheets. The ARB process up to eight cycles (an equivalent thickness strain of 6.4) is successfully performed at ambient temperature. TEM observation reveals that ultrafine grains, hardly containing the dislocation interior, begin to develop at the third cycle, and after the sixth cycle they cover most of regions of samples. The morphology of ultrafine grains formed is different from that of aluminum alloys. Tensile strength of the ARB-processed copper increases with the equivalent strain up to a strain of ~3.2, in which it reached 390 MPa, ~2.1 times higher than the initial value. However, the strength hardly changed at the strain above ~3.2.