Journal of the Society of Materials Science, Japan
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
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Volume 53, Issue 7
Displaying 1-17 of 17 articles from this issue
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  • In-situ Synchrotron Measurement of Thermal Stress in Textured Copper Thin Films during Thermal Cycling
    Keisuke TANAKA, Toshimasa ITO, Yoshiaki AKINIWA, Hiroyuki OHTA
    2004 Volume 53 Issue 7 Pages 728-733
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.728
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    Copper thin films with a thickness of 600nm were sputtered on the undercoating. The top layer of the undercoating was TiN with a thickness of 50nm sputtered on SiO2 layer with the thickness of 300nm on the Si wafer. Films were subjected to heating to 500°C in vacuum followed by cooling. During heat cycling, the in-situ measurement of the X-ray profiles and the stress of the film was conducted by using X-rays from a synchrotron radiation source of SPring-8. The stress was determined from the measured strains using the two-tilt version of the sin2ψ method assuming the equi-biaxial stress state. The half-value breadth of the diffraction profiles decreased during heating and then increased during cooling. This behavior of the half-value breadth corresponded to the decrease and increase of the lattice defects during heat cycling. The lattice constant measured by X-rays was a linear function of the temperature. With respect to the stress, the heating process to 180°C decreased the stress from about 200MPa to about-100MPa, and then, at higher temperatures, the compressive stress was relaxed by creep. The stress in the film was almost zero above 400°C. In the cooling process, the tensile stress was built up with decreasing temperature. After heat cycling, the residual stress was increased to about 350MPa. The experimental data was compared with the prediction based on the model proposed by Thouless et al. The model was based on the stress relaxation by various creep mechanisms. The predicted variation of the stress during heat cycling agreed well with the experimental results.
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  • Oxidization of Thermal Barrier Coatings and Spalling Stress Analyzed with Synchrotron X-Rays
    Kenji SUZUKI, Takahiro KUBO, Keisuke TANAKA, Yoshiaki AKINIWA, Hideki ...
    2004 Volume 53 Issue 7 Pages 734-739
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.734
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    As the bond coating, NiCoCrAlY powder was atmospheric plasma-sprayed on the Ni based super-alloy (In738LC), and the thickness of the bond coating was 0.15mm. Zirconia powder with 8mass% yttria was atmospheric plasma-sprayed as the top coating, and the thickness was 0.3mm. To oxidize the specimen, the specimens were kept in air at 1373K for 0, 500, 1000 and 2000h. The cross section of each oxidized specimen was observed with a scanning electron microscope. The thermally grown oxide (TGO) consists of the alumina layer and the composite oxide layer. The thickness of alumina layer stopped to increase after 500h exposure, while the thickness of the composite oxide layer incresed monotonically. The TGO grew at the convex part of the bond coating, and pushed up the top coating. As a result, the spalling crack was initiated near the convex part. The spalling stress for each oxidized specimen was estimated by the hybrid method using the stress data obtained by laboratory X-rays and high energy synchrotron X-rays. The top coating without the oxidization did not have the spalling stress. For the oxidized specimen, the spalling stress was small beneath the surface, and steeply increased near the interface between the top and the bond coating. The spalling stress near the interface was about 200MPa. The distribution of the spalling stress for the case of the 1000h exposure was similar to that for the case of 500h. The TGO promotes the spallation of the top coating, and the distribution of the spalling stress corresponds to the observed position of spalling cracks.
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  • Effects of Residual Stress on Critical Strain for Macroscopic Crack Formation on Thermal Spray Coatings
    Koichi AKITA, Shogo TOBE
    2004 Volume 53 Issue 7 Pages 740-745
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.740
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    A new evaluation method of mechanical strength of thermal spray coatings using an acoustic emission (AE) measurement during bending loading was proposed. Plasma thermal spray molybdenum coatings deposited on steel specimens were used in this study. In-situ microscopic observations on the cross-section of the coating and acoustic emission measurements during bending loading were performed and the microscopic fracture process was investigated. Microscopic cracks grew from initial microscopic cracks and pores at the early stage of loading. Microscopic cracks were joined and a macroscopic crack formation was started at a certain bending strain. The macroscopic crack propagated towards to the substrate. Finally, the interface cracking and delaminating were occurred. The cumulative AE event rapidly increased when the macroscopic crack formation started. Therefore, the critical strain for the macroscopic crack formation of the thermal spray coating can be determined by the rapidly increasing point of the cumulative AE event. The effect of the residual stress of the coating on the critical strain for the macroscopic crack formation was investigated. The specimens having five kinds of the residual stress levels were prepared by in-situ bending during spraying. The residual stresses of coatings were measured using a synchrotron radiation. The critical strain for the macroscopic crack formation became higher on the specimen having higher compressive residual stress. That is the compressive residual stress increases the mechanical strength of the thermal spray coating.
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  • Residual Stress in Uni-Directionally Deformed Surface Layer by Shotpeening on Spring Steel
    Takayuki SAKAKIBARA, Yoshihiro SATO
    2004 Volume 53 Issue 7 Pages 746-751
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.746
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    High durability is required for automotive engine valve springs. To ensure the performance of spring, it is necessary to evaluate and measure the residual stress distribution of spring surface and a downward direction from the top surface. Generally, it has been assumed that the residual stress of a material surface treated by the shot peening is uniform. The round and spiral shape of a coil spring brings various peening angles corresponding to the surface location, then the directional shot angles may leads to a non-uniform residual stress on the coil spring surface. It is well known that the material received the directional deformation shows the non-linear 2θ-sin2ψ diagram (ψ-split) due to the triaxial stress state.
    In this study, the residual stress distributions of spring materials deformed by the shot peening with different angles were measured and, also the microstructure especially for carbide precipitates was examined by using field emission type scanning electron microscope (FE-SEM). The non-linearity in the
    2θ-sin2ψ diagram was revealed for the shot peening samples. The extent of ψ-split became larger with the increasing shot peening angle and was dependent not only on the mass fraction of carbide particles but also on the carbide particles size distribution.
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  • Measurement of Stress Distribution Near Notch and Fatigue Crack in Ultra-Fine Grained Steel by Synchrotron Radiation
    Yoshiaki AKINIWA, Hidehiko KIMURA, Keisuke TANAKA
    2004 Volume 53 Issue 7 Pages 752-757
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.752
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    Stress distribution near a single-edge notch and a fatigue crack in steel plates of ultrafine-grained surface layers (SUF steels) was measured by monochromatic X-rays from synchrotron radiation. For the notched specimen, the stress distribution was measured at PF (Photon Factory). The diameter of irradiated area was 100μm. The diffracted X-rays were recorded by an imaging plate. Residual stresses and loading stresses ahead of the notch were determined by the cosα method. when the distance from the notch root was larger than 400μm, the measured stresses agreed well with the values calculated by FEM. Then the stress distribution near a fatigue crack was measured by sin2ψ method at SPring-8 (Super Photon Ring-8). The slit was adjusted so that the irradiated area became constant of 100×100μm2 irrespective of ψ angle. The loading stresses and residual stresses ahead of crack tip agreed very well with the calculated results. The residual stress on the wake of the fatigue crack was compared with the result simulsted by Newman's method. The crack opening stress intensity factor calculated by the measured residual stresses agreed with the experimental result.
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  • Study on Correlation between Minimum Irradiation Area and Microstructure in Micro X-Ray Stress Measurement
    Yoshihisa SAKAIDA
    2004 Volume 53 Issue 7 Pages 758-764
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.758
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    In order to establish an optimum local stress measurement by the sin2ψ method using micro X-ray beam, Debye-Scherrer rings of three kinds of polycrystalline Al2O3, and Al2O3-10vol%ZrO2 were measured as a function of X-ray irradiation area. Each Debye-Scherrer ring image was obtained from image plate by Cu-Kα or Fe-Kα radiations. X-ray diffraction pattern was also detected from the measured Debye-Scherrer ring image. And then, a correlation between X-ray irradiation volume and X-ray diffraction pattern was examined for each material. The minimum X-ray irradiation volume, where X-ray diffraction pattern and local stress field were approximately equivalent to that from a myriad of grains existed in model materials, was determined. As a result, the minimum irradiation volume was found to correspond to the microstructural volume in which about 104 grains existed randomly. Furthermore, by oscillating the X-ray incident angle, the minimum irradiation volume lowered at the volume in which about 2.8×103 grains existed. Finally, it was confirmed that local stress of polycrystalline Al2O3 could be successfully measured by Synchrotron micro X-ray beam.
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  • Microstructure and Mechanical Properties of MM/SPS Processed TiC Dispersed SUS316L Compacts
    Susumu MATSUNO, Masashi TAKAMI, Kei AMEYAMA
    2004 Volume 53 Issue 7 Pages 765-771
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.765
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    Mechanical milling (MM) is one of severe plastic deformation process which enables to introduce very high strain into materials. Spark Plasma Sintering (SPS) ables to fabricate sintered compacts in a short period of time, under low pressure as well as at low temperature due to its powder surface activating effect. Combining these two processes, the MM/SPS process is applied to the powders of SUS316L, Ti and graphite. The powder was sintered by spark plasma sintering (SPS) for 3.6ks at 1376K. As the result of it, a spherical TiC containing Mo was formed, fine grain structure was observed. Fine grain structure with its grain size of 300nm composed of γ phase and spherical TiC of the size; 150nm was obtained. It was confirmed that these fine TiC restrains the grain growth. The compressive strength of the sintered MM powder is much higher than that of the sintered MM powder without Ti, C.
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  • A Neutron Diffraction Study on Work-Hardening Mechanism for a Pearlite Steel
    Atsuomi KANIE, Yo TOMOTA, Tetsuya SUZUKI, Shuki TORII, Atsushi MORIAI, ...
    2004 Volume 53 Issue 7 Pages 772-775
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.772
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    The work hardening and the internal stress averaged in each constituent, so called “phase stress” in a pearlite steel were studied by means of neutron diffraction techniques, time-of-flight (TOF) and angler dispersion (AD) methods. The overall diffraction profiles obtained by the TOF method indicates that the cementite (122) and feirrite (110) peaks are preferable to be employed for the in situ neutron diffraction with the AD method during tensile testing. The stress partitioning between cementite and ferrite after the onset of plastic deformation is evidently found. Hence, the high work-hardening of the pearlite structure is demonstrated to be caused by the generation of phase stress. The influence of ferrite block orientation on the residual phase stress after tensile deformation is shown. Then, the heterogeneous plastic flow at several classes is speculated, which makes complicate to estimate the stress in each constituent from (hkl) lattice plane strains measured.
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  • Compression Molding and Mechanical Properties of Green-Composite Based on Ramie/PLA Non-Twisted Commingled Yarn
    Teruo KIMURA, Masahiro KURATA, Tatsuki MATSUO, Hirokazu MATSUBARA, Tad ...
    2004 Volume 53 Issue 7 Pages 776-781
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.776
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    In recent years, increased emphasis has been placed on developing the environmentally friendly biodegradable composites with the goal of protecting the environment. In this paper, the ramie/PLA biodegradable composites were molded and their mechanical behaviors were discussed. The non-twisted commingled yarn constructed with ramie and PLA fibers as reinforcement and matrix respectively was pre-molded to achieve the good penetration and dispersion of matrix and reinforcement. The compression molding with heating was performed to melt PLA fibers, and the green-composites reinforced by uni-directionally oriented ramie fiber were obtained. The volume fraction of ramie fiber was varied for wide range, and the tensile, bending and impact tests were performed for the molded composite. Especially, the results of bending test were compared with those of the composite based on the usual twisted commingled yarn. The microscopic observation was also carried out to examine the fracture mode of composite. It is concluded here that the fairly higher tensile and bending strength and modulus were obtained for our molded composites. This may be caused by the good penetration of matrix between fibers, good dispersion of fibers and also the uni-directionally oriented fibers. Especially, the impact value was fairly larger than that of PLA matrix at the higher volume fraction of ramie fiber.
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  • Effect of Crack Position on Slant Crack Growth in Fretting Fatigue
    Toru KIMURA, Kenkichi SATO
    2004 Volume 53 Issue 7 Pages 782-787
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.782
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    It is well known that fretting fatigue cracks usually initiate in the contact area near contact edge and grow obliquely to the normal direction of the contact surface. In order to determine the fretting fatigue crack growth mechanism, the stress intensity factors KI and KII have been widely used. The authors have established a scheme and software to obtain the values of KI and KII of the oblique fretting fatigue cracks which are initiated at the contact edge and subjected to arbitrarily distributed contact pressure with friction. In this paper, the solution has been expanded to the fretting fatigue cracks initiated near contact edge. The calculated results of stress intensity factors show that the distance between crack position and contact edge markedly affects on the values of KI and KII. Crack propagation direction has been estimated by using maximum tensile stress (MTS) criterion according to the calculated values of KI and KII. The effect of mode II stress intensity factor KII due to normal and tangential stress distributions near the contact edge on the crack propagation direction has been discussed. It has been concluded from the present study that the slant crack growth in fretting fatigue results from crack initiation near contact edge.
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  • Residual Stress and Microstructural Damage of Polycrystalline Copper Thin Films after Thermal Cycling
    Keisuke TANAKA, Toshimasa ITO, Yoshiaki AKINIWA, Hiroyuki OHTA
    2004 Volume 53 Issue 7 Pages 788-794
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.788
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    Copper thin films with a thickness of 600nm were coated on the undercoating by sputtering. The top layer of the undercoating was TiN with the thickness of 50nm sputtered on SiO2 layer on Si wafers. Films were subjected to heat cycling to various temperatures ranging from 50 to 500°C. The surface topography was examined by atomic force microscopy and scanning electron microscopy, The X-ray diffraction method was used to measure the residual stress and the intensity ratio of 222 to 200 diffraction. Heating cycles to temperatures below 200°C did not induce any remarkable change in the microstructure and topography. By heating to 500°C, the crystalline size increased from 0.5μm to 1.1μm. The volume fraction of hillocks increased after heating cycles above 250°C. At the same time, the intensity ratio of 222 to 200 diffraction increased, while the half-value breadth decreased. The residual stress at room temperature was equi-biaxial tension. The residual stress increased from 270MPa before heating to 350MPa after heating cycle to 500°C. The variation of the measured residual stress with heating temperature does not agree with the prediction based on the model proposed by Thouless et al.
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  • Creep-Fatigue Life Prediction for Permanent Magnet Type Eddy Current Retarder
    Yasutaka NOGUCHI, Mitsuo MIYAHARA, Kenji IMANISHI, Akira SAITOH, Nobut ...
    2004 Volume 53 Issue 7 Pages 795-800
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.795
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    The strain range partitioning method was applied to a creep-fatigue life prediction of the rotor of the permanent magnet type eddy current retarder, which is a braking system equipped in heavy trucks. Transient heat transfer analysis and elastic-plastic-creep thermal stress analysis were conducted with a three-dimensional finite element model in order to evaluate the inelastic strain caused by repetition of braking. On the basis of analytical results and creep-fatigue properties of rotor steels, creep-fatigue life of the rotor was predicted by the strain range partitioning method and creep-fatigue damage rule based on the strain range partitioning concept. The predicted lives were well corresponded with those in thermal cycle tests with the actual retarder. Furthermore, in order to increase the braking torque and extend the life of the rotor, the new rotor steel was developed. The developed steel has lower electrical resistivity and higher strength at high temperature than the conventional rotor steel. It was found that the developed steel rotor has higher braking torque and longer creep-fatigue life than those of the conventional steel rotor.
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  • Estimation of Creep Constitutive Law for Cr-Mo-V Material in Turbine Rotor Using Indentation Creep Test
    Shinsuke SAKAI, Satoshi IZUMI, Takashi MURAKAMI, Akito NITTA, Jun-ichi ...
    2004 Volume 53 Issue 7 Pages 801-805
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.801
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    In residual life evaluation of fossil power plants, improvement of accuracy of creep damage evaluation is extremely important. One of the powerful non-destructive evaluation methods is hardness test. This method is effective because it enables us the on-site evaluation and the results are obtained without laborious work. In this paper, the Vickers hardness test not at ambient but at high temperature is applied to turbine rotor material and the method for evaluating the creep constitutive law is newly developed. Firstly, the method to derive the creep constitutive law from hot hardness test is formulated. In this method, only the hot harness test results together with only one tensile creep test result are required at around operation temperature to evaluate the Norton law. Secondly, the formulation is applied to the experimental results of hot hardness test. It is shown that results evaluated by the proposed method agree well with those obtained from tensile creep tests.
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  • Tension Test Method and Thermal Degradation of Fatigue Strength for Unidirectional CFRP Ring
    Tomohiro NARUSE, Toshio HATTORI, Haruo MIURA, Kazuki TAKAHASHI
    2004 Volume 53 Issue 7 Pages 806-811
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.806
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    Fiber reinforced plastic (FRP) rings, reinforced along the hoop direction of the ring are used in high speed rotors and pressure vessels because of their high strength and rigidity and their low density. To confirm the reliability of these products, we must evaluate how they degrade in humidity, sunlight, and under thermal load. Thus, we studied the thermal degrading properties of unidirectional carbon FRP (CFRP) rings. Firstly, we developed an evaluating method of hoop directional strength based on the ring tensile test. During the ring tensile test, hoop stress at the inner surface becomes much larger than mean stress. This distribution is based on its bending force, and the hoop stress distribution is influenced by its thickness and the frictional force between the FRP ring and the cylindrical jig. We measured the tensile strength of CFRP rings by doing the ring tensile test, and also calculated hoop stress distribution using the Finite Element Method along with considering frictional problems. Then, we measured the thermal reduction of fatigue strength of unidirectional CFRP rings by doing the ring tensile test. To evaluate the fatigue strength degrading property, we applied Arrhenius's equation to confirm the relation between the temperature and the time. Using these evaluating methods we can predict thermal reduction of fatigue strength under the temperature and exposure time.
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  • Influence of Total Sputtering Pressure and Work Voltage on the Optical and Electric Properties of ITO Film onto Unheated Polymeric Substrate Produced by the Inclination Opposite Target Type DC Magnetron Sputtering
    Dohoon SHIN, Ri-ichi MURAKAMI, Daisuke YONEKURA, Yunhae KIM
    2004 Volume 53 Issue 7 Pages 812-817
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.812
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    The ITO film was deposited onto the polyethylene terephthalate (PET) substrate at room temperature by the inclination opposite target type DC magnetron sputtering equipment. An indium tin alloy (In2O3 (90wt%)+SnO2 (10wt.%)) target was used. The total sputtering pressure and the work voltage were varied from 0.18 to 0.8Pa and from -10 to -90V, respectively. The effects of total sputtering pressure and work voltage on the optical and electric properties of ITO film were discussed. The experimental results obtained were summarized as follows: (1) The ITO film produced at room temperature had microstructure in which a X ray diffraction peak is not clear, regardless of the total sputtering pressure and the work voltage. (2) For PET film deposited ITO film, an optical transmittance was over about 70% at the wave length of 600nm. (3) The absorption edge shifted to short the wave length with decreasing the total sputtering pressure and with increasing the work voltage. (4) For the deposited ITO film, the lowest electrical resistivity was about 6.10×10-4Ω·cm at the sputtering pressure of 0.51Pa when the sputtering pressure increased from 0.18Pa under a constant of -70V.
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  • Effect of Preparation Conditions on Pore Structure and Heavy Oil Sorption of Charcoals
    Norio IWASHITA, Yoko NISHI, Yoshihiro SAWADA, Michio INAGAKI
    2004 Volume 53 Issue 7 Pages 818-825
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.818
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    Charcoals were prepared under various conditions of carbonization from three kinds of plants: balsa (Ochroma lagopus Sw), giant ipil-ipil (Leucaena leucocephala (Lam.) de Wit) and mousou chiku (Phyllostachys pubescens). The pore structure of the various charcoals was observed on fractured cross-sections under SEM and was evaluated utilizing mercury porosimetry. The sorption capacity of the charcoals for A-grade heavy oil was determined by direct soaking in oil. It was found that the pore structure of the charcoals depended strongly on, not only, the precursor plants but also carbonization conditions, particularly heating rate. Balsa charcoals prepared with a heating rate of 50°C/min. under vacuum gave a relatively high sorption capacity for A-grade oil, approximately 30g/g of charcoal. The other two charcoals, derived from giant ipil-ipil and Mousou chiku, had a considerably lower capacity, approximately 1.5g/g-carbon. The dependence of pore occupancy, the ratio of volume of oil sorbed to total pore volume, on the average pore radius indicated that pores with a diameter above 1μm were largely responsible for heavy oil sorption.
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  • Fracture, Its Evaluation and Suppression
    III: Surface Modification for Suppression of Crack Initiation and Propagation
    Hitoshi SOYAMA
    2004 Volume 53 Issue 7 Pages 826-832
    Published: July 15, 2004
    Released on J-STAGE: June 03, 2009
    DOIhttps://doi.org/10.2472/jsms.53.826
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