PRICM7

Volumes 654-656

doi: 10.4028/www.scientific.net/MSF.654-656

Paper Title Page

Authors: Jozef Zrník, Sergey V. Dobatkin, George Raab, Libor Kraus
Abstract: The present work deals with grain refinement in low carbon steel (AISI 1010) by severe plastic deformation (SPD). The effect of structure modification was evaluated with respect to thermomechanical (TM) treatment of steel prior to SPD. The grain refinement was accomplished during warm angular channel pressing (ECAP) at 300°C. The evolution of microstructure during equal channel angular pressing (ECAP) was studied using SEM and TEM of thin foils. Ultrafine-grained structure development is described in relation to strainintroduced. At lower strain applied, the subgrain and/or polygonized structure was frequently found. Due to increased deformation temperature, the dynamic recovery contributed to structure refinement in both structural states. The amount of high angle boundaries increased with higher ECAP strain and was higher in TM-processed steel. There was only an indistinctive difference in structure refinement, considering different initial structures of the steel.The deformation behaviour of UFG steel in dependence on processing conditions was evaluated by a tensile test and correlated with structural characteristics.
1223
Authors: Hisashi Sato, Yuichi Kubota, Eri Miura-Fujiwara, Yoshimi Watanabe
Abstract: Effects of the transformation temperature on formation behavior of the wear-induced layer in Fe alloys are investigated using Fe-33mass%Ni and Fe-30mass%Ni alloys. Martensitic transformation temperature (Ms) and reverse transformation temperature (As) of Fe-33mass%Ni alloy are lower than those of Fe-30mass%Ni alloy. Microstructure of the wear-induced layer in Fe-33mass%Ni alloy was single austenite phase (γ) with fine grain. On the other hand, the wear-induced layer in Fe-30mass%Ni alloy consists of martensite (α’) and γ with fine structure. This difference is due to the difference of As between these Fe-Ni alloys. Moreover, the microstructure of the wear-induced layer has no dependence on the distribution of α’ in initial microstructure. From obtained results, it is concluded that the formation of the wear-induced layer in Fe alloys is mainly affected by As.
1227
Authors: Takumi Ikeda, Hiroyuki Miyamoto, Toshiyuki Uenoya, Satoshi Hashimoto, Alexei Vinogradov
Abstract: The pure copper single crystals with specific crystallographic orientated were subjected to ECAP for one pass at room temperature. Two types of shear bands were observed. Type 1 shear bands were constructed with clusters of distorting micro shear bands and matrix. Micro shear band and matrix were delineated by large-angle grain boundaries, and these two orientations are in a twinning relationship. Parallel sets of deformation twins were observed in the matrix. Type 2 shear bands had no crystallographic feature, and shear band and matrix were considered as low-angle grain boundaries. Deformation twin was not observed both in matrix and the shear bands.
1231
Authors: Takumi Haruna, Yuichi Nakagawa, Daisuke Terada, Naoki Takata, Nobuhiro Tsuji
Abstract: We have investigated the susceptibility to hydrogen embrittlement of interstitial-free (IF) steel with ultrafine-grained microstructure produced by accumulative roll-bonding (ARB) process. The ARB process was conducted to as-received IF steel at 773 K, and repeated to five cycles. The as-received and the ARBed IF steels were cut into tensile specimens, and then hydrogen was electrochemically charged to the specimens in a sulfuric acid solution of pH 2.5 at a cathodic current density of 50 A m-2 for several charging times. Immediately after the hydrogen-charging process, tensile test was conducted at ambient temperature and an initial strain rate of 3.3 x 10-4 s-1. Besides, state and amount of hydrogen absorbed in the specimen were determined with a thermal desorption gas spectroscopy (TDS) at a heating rate of 5.6 x 10-2 K s-1. As a result, almost no hydrogen was absorbed in the as-received IF steel charged for a long time of ca. 300 ks, and a fracture strain of the steel was independent of the charging time. On the other hand, amount of hydrogen in the 5-cycle ARBed steel increased with an increase in the charging time, and the fracture strain decreased with an increase in the charging time, indicating that the ARBed steel exhibited susceptibility to hydrogen embrittlement.
1235
Authors: Kaveh Edalati, Z. Horita, Hiroshi Fujiwara, Kei Ameyama, Masaki Tanaka, Kenji Higashida
Abstract: Pure Ti powders were subjected to ball milling and subsequently high-pressure torsion (HPT) for consolidation. It is found that a fully dense (99.9%) disc with ultrafine grained structure (~50-300 nm) was produced. The strength and ductility were well comparable to those of ball-milled Ti-6%Al-4%V powders after hot roll sintering.
1239
Authors: Seung Won Lee, Daichi Akama, Z. Horita, Tetsuya Masuda, Shoichi Hirosawa, Kenji Matsuda
Abstract: This study presents an application of high-pressure torsion (HPT) to an Al-Li-Cu-Mg alloy (2091). The alloy was subjected to solid solution treatment at 505oC for 30 minutes and was processed by HPT under 6 GPa for 5 revolutions at room temperature. The hardness increased with straining and saturated to a constant level at 225 Hv. Aging was undertaken on the HPT-processed alloy at 100, 150 and 190oC for the total periods up to 9.3 days. The aging treatment led to a further increase in the hardness to ~275 Hv. It is shown that the simultaneous strengthening of the alloy due to grain refinement and age hardening was successfully achieved by application of HPT and subsequent aging treatment. The enhancement of the strength is prominent when compared with the application of a conventional rolling process.
1243
Authors: Yuji Kume, Masakazu Motohashi, Makoto Kobashi, Naoyuki Kanetake
Abstract: Compressive torsion process (CTP) which was developed by authors is effective process for grain and precipitates refinement of metallic materials with a severe plastic deformation. In the CTP, a cylindrical specimen is subjected to simultaneous compressive and torsional loading without change in its shape. However, metal flow and strain distribution in the processed specimen are not cleared, because the deformation is very large and complicated. In the present work, visualization of internal deformation of specimen processed by CTP was investigated using dual alloy etching technique. Two kinds of aluminum alloy were prepared by cutting on fan-like shape and alternately placed to a cylindrical shape. After CTPing, contrasts in the specimen were observed by polishing and etching. The internal distribution of shear strain was quantified by measuring the displacement of interface between the alloys. As a result, the visualization and quantification of internal deformation was successfully carried out using the technique. The internal strain distribution was varied not only in radial direction but also in longitudinal direction because of frictional constraint on the lateral face. A laminate contrast of the alloys observed on the vertical cross section was well related with the strain distribution in the specimen.
1247
Authors: Masahiro Shinsen, Mitsuaki Furui, Susumu Ikeno, Takekazu Nagae
Abstract: In present work, bar samples of pure copper and Cu-Zn alpha single phase alloys setting 20mm in diameter and 150mm in length processed by torsion in the rotation speed to 1rpm every 60° twist angles. Then, deformed samples were researched microstructure and their characteristics. Microstructures of non-deformation samples were isometric, however, deformed samples streaky. Elements of bar drawn 10×10mm mesh were developed parallelogram. It was trend angle of between stretchable direction in microstructures and torsion axis increased more torsion angles. It was coincident with between the angle and deformed direction of microstructures. Shear strain was calculated by twist angle by theoretical formula. Their value corresponded rough with measurement from mesh variation. Pure copper and Cu-Zn alpha phase alloys were similar deformation microstructure, but fracture twist angle in copper was more than Cu-Zn alloys, and it was trend fracture angle had decreased as concentration of Zn increased. This trend was difference of fracture elongation obtained in tensile test.
1251
Authors: Dmitry Orlov, Rimma Lapovok, László S. Tóth, Ilana B. Timokhina, Peter D. Hodgson, Debashish Bhattacharjee, Arunansu Haldar
Abstract: As-received hot-rolled 5.6 mm thick IF steel sheet was symmetrically/asymmetrically cold rolled at room temperature down to 1.9 mm. The asymmetric rolling was carried out in monotonic (an idle roll is always on the same side of the sheet) and reversal (the sheet was turned 180º around the rolling direction between passes) modes. Microstructure, texture and mechanical properties were analysed. The observed differences in structure and mechanical properties were modest, and therefore further investigation of the effects of other kinds of asymmetry is suggested.
1255
Authors: In Soo Kim, Nam Su Kwon, Saidmurod Akramov
Abstract: Aluminum alloy sheets have lower formability (r-value) than low carbon steel sheets in fully annealed condition. Because the texture of fully annealed aluminum alloy sheet is mainly consists of cube component {001}<100>, which shows low formability. Asymmetric rolling, one of the severe plastic deformations, gives rise to shear deformation texture through the Al sheet thickness. In this paper, the changes of texture components after the severe deformation and subsequent heat treatment in Al sheet were observed. The change of the formability after the severe plastic deformation and subsequent heat-treated Al sheets have been analyzed with the change of texture of Al alloy sheets.
1259

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