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Volume 77, Issue 9
Displaying 1-10 of 10 articles from this issue
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Special Issue on Crystallographic Orientation Distribution and Related Properties in Advanced Materials
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Toshiharu Morimoto, Fuyuki Yoshida, Yuji Kusumoto, Masahiko Oda, Jun Y ...2013 Volume 77 Issue 9 Pages 339-347
Published: 2013
Released on J-STAGE: September 01, 2013
JOURNAL FREE ACCESSThe ridging phenomenon of type 430 stainless-steel originates from the texture due to crystal plasticity anisotropy. Thus, to predict the antiridging property, we must continuously analyze the hot-rolling, hot-rolling and annealing, cold-rolling, cold-rolling and annealing textures. However, it has been previously difficult to analyze the recrystallization texture. We thus developed a model to predict the recrystallization texture coupled with the Taylor rolling model. Furthermore, the ridging index was calculated in order to estimate the plasticity in type 430 stainless-steels. The plasticity prediction method was applied to type 430 stainless-steel strips rolled at a low temperature with a high reduction rate in an actual tandem hot strip mill.
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Yohei Wadamori, Kentoku Hirayama, Hiroshi Fujiwara, Toshiyuki Uenoya, ...2013 Volume 77 Issue 9 Pages 348-352
Published: 2013
Released on J-STAGE: September 01, 2013
JOURNAL FREE ACCESSGrain boundaries can change their misorientation by absorbing lattice dislocations at relatively high temperature under moderate straining. The same phenomenon is believed to occur during severe plastic deformation down to room temperature leaving grain boundaries in the nonequilibrium state. Direct evidence of dynamic misorientation change of the grain boundary during severe plastic deformation was obtained in copper bicrystals subjected to equal-channel angular pressing (ECAP) for one pass. Marked dependence of misorientaion change on the initial orientation was revealed, and is associated with the unique slip patterns of ECAP, where the shear deformation is restricted to the narrow zone parallel to the intersecting plane of the two channels. The degree of change can be related to slip geometry in terms of grain boundary plane orientation.
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Hiroshi Kaneko, Tatsuhiko Eguchi, Hirofumi Inoue2013 Volume 77 Issue 9 Pages 353-360
Published: 2013
Released on J-STAGE: September 01, 2013
JOURNAL FREE ACCESSAge-hardened Cu-Ni-Si alloy strips with various recrystallization textures were analyzed to determine the effect of texture on Young's modulus in a polycrystalline material. The Cube orientation {001}〈100〉, the rolling direction (RD)-rotated Cube orientation {012}〈100〉, the BR orientation {362}〈853〉, the R orientation {231}〈346〉, and the Copper orientation {121}〈111〉 developed in the samples prepared under different rolling and heat-treatment conditions. The average grain size in these samples was about 5 μm. Young's modulus measured by resonance method was dependent on the fractions of the 〈001〉 and 〈111〉 crystal directions in the stress direction. The sample with a strongly developed Cube orientation showed the lowest Young's modulus, which was more than 30 GPa lower than that of the sample with highest Young's modulus in which the R and Copper orientation was developed. This variation corresponded to analytical value by Hill's approximation based on orientation distribution function (ODF). The larger volume fraction of precipitates in Cu-3.8Ni-0.9Si alloys compared to Cu-2.3Ni-0.7Si alloys had a small influence on Young's modulus.
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Natsuko Sugiura, Naoki Yoshinaga2013 Volume 77 Issue 9 Pages 361-367
Published: 2013
Released on J-STAGE: September 01, 2013
JOURNAL FREE ACCESSThe electro-deposited pure iron has a quite sharp and isotropic 〈111〉//ND fiber texture and needle shaped grain elongated in ND. This pure iron shows the r-value over 7 and it is difficult to explain such a high r-value only from the texture. In this study the deformation behavior of the electro-deposited pure iron was investigated to reveal the mechanism of the extremely high r-value. The slip lines on the surface after the deformation indicated that the particular {110} plane slips which are parallel to ND exclusively act in the specimen. The tensile deformation by this slip system does not need the thickness decrease. Thus the limitation of the active slip system is the main cause of the extraordinary high r-value. One possibility of the limitation is the ease of the continuity of the slip plane of the adjacent grains. Because both {110} slip plane and grain boundary are perpendicular to the surface, the slip planes of adjacent grains can connect easily.
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Regular Article
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Yoshito Takemoto, Kazuya Fujii, Shou Nakastuka, Takehide Senuma2013 Volume 77 Issue 9 Pages 368-374
Published: 2013
Released on J-STAGE: September 01, 2013
JOURNAL FREE ACCESSThe transformation behavior and microstructural changes of Ti-4Fe-7Al alloy during tempering were investigated by performing a hardness test and using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Within a brief time of 30 s during tempering at 450℃, the hardness rapidly increased to a maximum value of 600 Hv. The transformation behavior estimated from the increase in hardness indicated “a lower half of C-curve” in the TTT diagram, which suggests that the transformation occurs through certain thermal activation processes. However, it is difficult to assume that the transformation is controlled by the diffusion of substitutional atoms, since the mean diffusion distance of Fe atoms during tempering at 300℃ for 1×103 s, which also maximized the hardness, is much less than the distance of the nearest neighbors in the β structure. The structure of the α″ phase formed by tempering depends on both the temperature and holding time; a high temperature and a long time bring the α″ phase close to an hcp structure. As determined by XRD measurement, the sample tempered at 150℃ for 60 min was composed of the β phase. However, the ω and α″ phases were also detected in selected area diffraction (SAD) patterns. The sample tempered at 450℃ for 60 min consisted of a single α″ phase and exhibited a tweed structure in the TEM observation. Although the tweed structure seemed to contain only one α″-variant in the SAD patterns, HR-TEM observation revealed that it was composed of multiple nanoscale variants. It was considered that the marked grain refinement due to the nanoscale variants led to the extreme hardening of the sample and the significant broadening of XRD peaks. When the tempering temperature was increased to 600℃, the α phase and finely dispersed TiFe precipitates were formed after 60 min by the diffusion of atoms, which resulted in the softening of the sample and the sharpening of the XRD peaks.
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Masakazu Kobayashi, Yoshikazu Ohkawa, Hiroyuki Toda, Kentaro Uesugi, Y ...2013 Volume 77 Issue 9 Pages 375-384
Published: 2013
Released on J-STAGE: September 01, 2013
JOURNAL FREE ACCESSThe aim of this study was to establish a novel orientation analysis method that utilizes accurate grain position information, obtained by grain boundary tracking, to enable crystal-plasticity deformation analysis of polycrystalline metals. An experiment combining X-ray tomography and X-ray diffraction was performed, and the feasibility of the method was assessed by confirming the relation between diffraction spots and grains whose position was obtained by grain boundary tracking. Although some deviations were observed in diffraction spot intensity, owing to lack of beam stability and the extinction effect, several combinations of grain and spot features showed a high correlation. Furthermore, the diffraction spots originating from grains whose position was detected using grain boundary tracking showed higher correlation coefficients than those originating from grains whose position was detected using 3DXRD. In the case of the former grains, we could easily identify diffraction spots originating from specific grains by focusing on sets of grain and spot features having a high correlation. It was demonstrated that setting appropriate tolerance level enabled highly accurate orientation analysis, almost equivalent to that of 3DXRD.
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Takao Utsunomiya, Nobuyuki Ishii, Yoshihiko Hangai, Shinji Koyama, Soi ...2013 Volume 77 Issue 9 Pages 385-390
Published: 2013
Released on J-STAGE: September 01, 2013
JOURNAL FREE ACCESSAn aluminum foam sandwich, which consists of an aluminum foam core and two dense metallic face sheets, is a lightweight structural component with good energy and vibration absorption properties. In this study, using aluminum alloy die casting ADC12 plates containing large amount of gases, sandwich panels with metallurgical bonding between ADC12 aluminum foam core and dense aluminum sheets, of which the thickness was 3 mm and 1 mm, were fabricated by friction stir processing route. Through the observations of the dense sheets and the pore structure of aluminum foam core, the foaming condition for obtaining high porosity and good pore structure, and keeping a dense aluminum plate as surface plate simultaneously was discussed. Moreover, tensile tests were carried out on the fabricated aluminum foam sandwiches and it was shown that the bonding strength of interface is higher than the tensile strength of aluminum foam core.
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Yoshihiro Terada, Yoshinori Murata, Tatsuo Sato2013 Volume 77 Issue 9 Pages 391-397
Published: 2013
Released on J-STAGE: September 01, 2013
JOURNAL FREE ACCESSTensile creep tests were combined with detailed transmission electron microscopy in order to characterize the dislocation movements during creep and explain the creep properties of the Mg-Al-Ca AX52 die-cast alloy at 473 K. TEM observations indicate that dislocations are introduced within the primary α-Mg grain interior in the die-casting process, which consist of both basal and non-basal segments. The non-basal segments of the dislocations, having smoother curvature in the as die-cast state, partially exhibit steps parallel to the basal plane during high temperature exposure. The basal segments of the dislocations bow out and glide on the basal planes under stress, and the jogs follow the basal segments with the help of climb during creep. The easy glide of the basal segments of the dislocations controls the creep rates immediately after the stress application of the creep tests, while the creep mechanism for the alloy has been identified as the dislocation climb. By comparing the dislocation movements for the Mg-Al-Ca AX52 die-cast alloy with those for the Mg-Al AM50 die-cast alloy, it is inferred that the eutectic intermetallic phase covering the primary α-Mg grains decreases the climb velocity of the jogs during creep.
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Atsushi Sugihara, Soichiro Osaki, Ryoichi Nakatani2013 Volume 77 Issue 9 Pages 398-401
Published: 2013
Released on J-STAGE: September 01, 2013
JOURNAL FREE ACCESSWe investigated the compatibility of Ta-N and Ti-N thin films as a capping layer of CoFeB/MgO magnetic tunnel junctions on the basis of their resistivity, crystal structure, thermal stability and absorbability of boron. Ta-N and Ti-N thin films were prepared on MgO(001)/CoFeB structure by reactive sputtering using a gas mixture of Ar and N2 with varying N2 percentage (fN2). It was found that Ti-N prepared at fN2=30% had a resistivity of 220 μΩ cm, a nanocrystalline structure, a high thermal stability and good absorbability of boron compared with conventional Ta. These results suggest that Ti-N has potential as a novel capping material for CoFeB/MgO magnetic tunnel junctions.
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S. Ikeda, K. Ito, S. Nambu, M. Enoki2013 Volume 77 Issue 9 Pages 402-407
Published: 2013
Released on J-STAGE: September 01, 2013
JOURNAL FREE ACCESSA novel, noncontact, non-destructive evaluation technique for thin sheet specimens which may have internal cracks is drawing attention. In this technique, pulsed lasers generate ultrasonic waves on the surface of specimen, and an interferometer is used to measure the waves of the surface of specimen. Correlation between laser induced ultrasonic waves and size of internal cracks was investigated. Resin specimens with various size and location of internal cracks were prepared, and ultrasonic waves generated by YAG pulsed laser were measured by He-Ne laser interferometer. Results of FEM analysis and natural frequencies of flexural vibration were used to compare with the results of experiments. As a result, this method could detect location of cracks by using correlation coefficient and FFT peak frequency, and there were correlations between induced ultrasonic waves and size of internal cracks. This method was applied to inspect multi-layered-steel specimens with interlayer cracks.
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