Papers by Keyword: Accumulative Roll Bonding (ARB)

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Authors: Zhong Ming Liu, Hong Mei Chen, Wei Peng Guo, Jing Zhang, Yun Xue Jin
Abstract: Mg/Al alloy multilayered composites were produced by accumulative roll bonding (ARB) technique. The microstructures of Al and Mg alloy layers were characterized by scanning electron microscopy, and damping capacity of the composite was tested by dynamic mechanical analyzer.It can be found that the diffusion layers were produced in Al and Mg alloy layers, and the diffusion layers increased with increasing of the ARB pass. With the increasing of ARB pass, the room temperature damping value of Mg/A1 multilayered composite presented a downward trend. The temperature damping spectrum of the composite had two internal friction peaks, with the increasing of the ARB pass, the peak height of P1 peak increased gradually and P2 peak moved to low temperature gradually.
838
Authors: Rintaro Ueji, J. Taniguchi, N. Sumida, Katsushi Tanaka, Nobuhiro Tsuji
Abstract: Internal stress field in a severely deformed aluminium with ultrafine grained microstructure has been studied by convergent-beam electron diffraction (CBED) technique in transmission electron microscopy (TEM). A commercial purity aluminium (99.1%Al) sheet was highly strained by the accumulative roll-bonding (ARB) process to evolve an ultrafine grained structure. Higher-order Laue zone (HOLZ) lines in the incidence disk of the ] 12 1 [ zone axis have been observed at various positions within an identical ultrafine grain. The key finding is that the HOLZ line pattern taken from the vicinity (~50nm) of the grain boundary (lamellar boundary) looses ) 1 1 0 ( mirror symmetry, whereas the pattern from the grain centre has the symmetry. The former and the latter represent the existence of a large non-hydrostatic stress field and a small internal stress field, respectively. The magnitude of the internal stress becomes larger with approaching to a grain boundary.
123
Authors: Ana Carmen C. Reis, Leo Kestens, Yvan Houbaert
Abstract: Titanium alloyed interstitial free steel was processed by means of accumulative roll bonding (ARB) in order to obtain an ultrafine grained structure. Ten consecutive rolling passes were applied at 480°C with a nominal reduction of 50% per pass and an intermediate annealing treatment of 5 min. at 500°C. A total true strain was obtained of evM = 8.0 which corresponds to an accumulated reduction of 99.9%. Orientation imaging microscopy was used to evaluate textures and microstructures. A pronounced lamellar structure was observed until the 5th pass with an incidence of high angle grain boundaries predominantly parallel to the rolling direction. After the 6th pass (evM = 4.8) an increased fragmentation perpendicular to the rolling direction starts to develop in spite of the lamellar microstructure with an average spacing of approximately 1 µm. From the 7th pass onwards (evM ≥ 5.6) a random high angle grain boundary distribution develops which results in a more equi-axed ultrafine microstructure after the 9th pass (evM = 7.2) with an average grain width of 200 nm. As the rolling is carried out without lubrication, the surface areas display a slightly more fragmented structure than the midlayer sections and typical shear texture components are present in these surface zones (<110>//ND and <211>//ND fibre). Although the sheets are stacked upon each other after each subsequent pass, the shear strain microstructural and textural features are rapidly decomposed in the midlayer in each subsequent rolling pass which is clearly revealed by the cross sectional orientation scan on the composite sample. Hence it cannot be concluded that the surface shear strain significantly contributes to the grain fragmentation in the bulk volume of the composite sample.
351
Authors: Nobuhiro Tsuji, K. Shiotsuki, Hiroshi Utsunomiya, Yasukazu Saito
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Authors: Hiromoto Kitahara, Nobuhiro Tsuji, Yoritoshi Minamino
Abstract: Martensite transformation of the ultrafine grained (UFG) austenite fabricated by the accumulative roll bonding (ARB) process was studied. The Fe-28.5at.%Ni alloy sheet was severely deformed in austenite state by the ARB process up to 5 cycles. The ARB processed sheet had the ultrafine lamellar boundary structure. The mean lamellar spacing was 230 nm in the 5 cycles specimen. The sheets ARB processed by various cycles were cooled down to 77 K to cause the martensite transformation. Martensite transformation starting (Ms) temperature decreased with increasing the number of the ARB process. The Ms temperature of the ultrafine lamellar austenite in the 5 cycles specimen was 225 K, which was lower than that (247 K) of the conventionally recrystallized specimen with mean grain size of 22 μm. The martensite having characteristic morphologies appeared from the UFG austenite, although the martensite transformed from the coarse-grained specimen showed typical plate (or lenticular) morphology. The strength of the nano-martensite transformed from the UFG austenite was about 1.5 times higher than that of the UFG austenite, and it reached to 970 MPa.
913
Authors: Hamidreza Jafarian, Ehsan Borhani, Akinobu Shibata, Daisuke Terada, Nobuhiro Tsuji
Abstract: In this paper, martensitic transformation from ultrafine grained (UFG) austenite fabricated by accumulative roll bonding (ARB) process in a metastable austenite alloy was studied. Microstructural observations and crystallographic analysis were carried out by FE-SEM/EBSD. The results showed that elongated UFG austenite having 200-300 nm in thickness surrounded by high angle boundaries was obtained after 6 cycles of the ARB process. The martensite transformed from the UFG austenite showed characteristic morphology and texture. The martensite transformation starting (Ms) temperature increased after 1 cycle ARB, which is related to increasing amount of nucleation sites, such as low angle boundaries, introduced during early stage of ARB process. In contrast, by increasing the ARB cycles, Ms temperature decreased. Decreasing the Ms temperature could be correlated to strengthening of austenite by the ARB process.
361
Authors: P. Chekhonin, B. Beausir, J. Scharnweber, C.G. Oertel, J. Jaschinski, Tina Hausöl, Heinz Werner Höppel, Heinz Günter Brokmeier, Werner Skrotzki
Abstract: The plastic anisotropy was studied on aluminium sheets with layers of different purity (A: 5N and B: 2N+) produced by accumulative roll bonding (ARB). Both material layers show a contrasting recrystallization behavior where A and B are discontinuously and continuously recrystallized, respectively. Global textures were measured by neutron diffraction. The mechanical anisotropy was measured by tensile testing after different numbers of ARB cycles. The planar anisotropy decreases with the number of ARB cycles while the normal anisotropy reaches a plateau after 4 cycles. Simulations of the Lankford parameters were carried out with the help of the viscoplastic self-consistent scheme (based on the global texture) and compared with the experimental data. Deviations of the simulated values from those of experiment are discussed with regard to through-thickness texture and material heterogeneities.
151
Authors: Tadashiege Nagae, Nobuhiro Tsuji, Daisuke Terada
Abstract: Accumulative roll-bonding (ARB) process is one of the severe plastic deformation processes for fabricating ultrafine grained materials that exhibit high strength. In aluminum alloys, aging heat treatment has been an important process for hardening materials. In order to achieve good mechanical properties through the combination of grain refinement hardening and precipitation hardening, an Al-4.2wt%Ag binary alloy was used in the present study. After a solution treatment at 550°C for 1.5hr, the alloy was severely deformed by the ARB process at room temperature (RT) up to 6 cycles (equivalent strain of 4.8). The specimens ARB-processed by various cycles (various strains) were subsequently aged at 100, 150, 200, 250°C, and RT. The hardness of the solution treated (ST) specimen increased by aging. On the other hand, hardness of the ARB processed specimen decreased after aging at high temperatures such as 250°C. This was probably due to coarsening of precipitates or/and matrix grains. The specimen aged at lower temperature showed higher hardness. The maximum harnesses achieved by aging for the ST specimen, the specimens ARB processed by 2 cycles, 4 cycles and 6 cycles were 55HV, 71HV, 69HV and 65HV, respectively. By tensile tests it was shown that the strength increased by the ARB process though the elongation decreased significantly. However, it was found that the tensile elongation of the ARB processed specimens was improved by aging without sacrificing the strength. The results suggest that the Al-Ag alloy having large elongation as well as high strength can be realized by the combination of the ARB process for grain refinement and the subsequent aging for precipitation hardening.
851
Authors: Nobuhiro Tsuji, Shinya Okuno, T. Matsuura, Yuichiro Koizumi, Yoritoshi Minamino
2667
Authors: O. Al-Buhamad, M. Zakaria Quadir, Michael Ferry
Abstract: A multilayered sheet composite of commercial purity Al and Al-0.3%Sc alloys was produced by accumulative roll bonding. The final sheet material consisted of 64 ultra fine grained layers, each of ~7.8mm in thickness. The as-deformed material was annealed at temperatures ranging from 250 to 350°C to study the changes in microstructure and their associated influence on mechanical properties. The as-deformed structures largely comprised of high angle grain boundaries in the Al layers and low angle grain boundaries in the Al(Sc) layers. During annealing, the structures in the Al(Sc) layers remained unaltered, whereas the Al layers recrystallized rapidly to the full layer thickness. The mechanical properties of the Al-Al(Sc) composite were measured and found to be unique in strength and ductility with annealing temperature having a significant influence on these properties.
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