All issues
Volume 67, Issue 10
Displaying 1-14 of 14 articles from this issue
- |<
- <
- 1
- >
- >|
-
Keiyu Nakagawa, Teruto Kanadani, Hatsujiro Hashimoto2003 Volume 67 Issue 10 Pages 521-527
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn Al-Si alloys, it is known that at the pre-aging stage clusters are generated which result in the growth of Si phase precipitates during the precipitation process. In this paper, we use a transmission electron microscope (TEM) to observe the microstructure of Al-Si alloys from immediately after quenching to the onset of precipitation. The results reveal the presence of streak regions immediately after quenching that are thought to be Si clusters, and these are coherent with the {111}matrix. At the initial stage of aging, plate-like Si crystals are observed. Moreover, the plate-like structure of the observed Si crystals contradicts the round shape previously described. We propose that the streak regions that appear immediately after quenching act as nuclei for the plate-like Si crystals. As the aging time increases, the plate-like Si crystals increase in length and thickness, and thus grow to become plate-like Si phases.View full abstractDownload PDF (2269K) -
Hideaki Kuramoto, Kazuhiro Matsugi, Kohsei Kawahara, Osamu Yanagisawa2003 Volume 67 Issue 10 Pages 528-537
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe densification rate of Cu-Al2O3 composite was measured and analyzed to investigate the influences of the alumina particles addition on the densification process in the spark sintering process.
The consolidation of Cu-10∼50 vol%Al2O3 composites proceeds due to the plastic flow of copper powder compact matrix. The effect of the alumina particles on the spark sintering of composites was analyzed based on the following equation, including the increase of relative density of composite compact, D−D0, that of copper (Dc-c−D0) and alumina (Dal-al−D0) and the particle contact probability of “copper-copper” ((1−Vp)2), “copper-alumina”(2Vp(1−Vp)) and “alumina-alumina” (Vp2).
(This article is not displayable. Please see full text pdf.)
\ oindentwhere η is a ratio of the relative density increase at “copper-alumina” particle contacts to that at “copper-copper” particles contacts, and η≤1. Moreover, D, Dc-c and Dal-al are the relative density of composite compact, copper and alumina at a given temperature and pressure, respectively, and Vp is the volume fraction of added alumina particles.View full abstractDownload PDF (979K) -
Akio Nishimoto, Masaaki Ando, Makoto Takahashi, Masatoshi Aritoshi, Ka ...2003 Volume 67 Issue 10 Pages 538-546
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to discuss the effect of a Ti intermediate layer on the strength of the friction-bonded joint of silicon carbide to copper, the microstructure of the joint interface was observed with a TEM. Specimens to be bonded were rods of pressureless-sintered SiC and oxygen-free copper. TEM observations revealed that reaction layers less than a few 10 nm thick were formed, which were identified as Cu, TiC, and Ti5Si3 on the basis of SAD pattern and EDX analyses. The Ti5Si3 layer was partly formed as discrete islands on the Cu side of the TiC layer. The Cu layer was located between SiC matrix and TiC layer, forming TiC/Cu double layers. The TiC/Cu double layers presented preferred orientation relationships with SiC, which can be expressed by the following equations.
(This article is not displayable. Please see full text pdf.)
\ oindentOn the other hand, the Ti5Si3 layer showed no preferred orientation relationship with SiC or Cu. In addition to these reaction layers, amorphous layers of Si oxide ∼100 nm thick were occasionally observed at the SiC/Cu interface. In the Cu-Ti mixing region adjacent to the joint interface, Cu4Ti particles ∼100 nm size in diameter were observed.View full abstractDownload PDF (1646K) -
Yong-Jai Kwon, Ichinori Shigematsu, Naobumi Saito2003 Volume 67 Issue 10 Pages 547-554
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe influence of tool rotation speed and microstructure on hardness and tensile properties of ultra-fine grained 1050 aluminum alloys produced by friction stir process (FSP) was experimentally investigated. FSP was carried out with only a single pass at tool rotation speeds ranging from 560 to 1840 min−1. For 1350 min−1 and below, the hardness within friction stir processed zone (FZ) was higher on the advancing side than on the retreating side. However, heat affected zone in which hardness drops was not formed near the FZ. For 1840 min−1, the hardness distribution was roughly uniform within the FZ. The average hardness of the FZ was isotropic and was elevated even to 37% compared with the starting material by increasing with decreasing the tool rotation speed, i.e. with decreasing the grain size. During tensile deformation, the friction stir processed materials with grain sizes of 2 μm and below exhibited an abrupt stress drop phenomenon at very early stage, which was not accompanied by a further increase in stress by strain hardening. In contrast, grain sizes of 2∼3 μm provided strain hardening after stress drop. On the other hand, for grain sizes of 3∼4 μm, stress reached a maximum value with strain hardening after a continuous transition from elastic to plastic deformation without the abrupt stress drop. The total elongation increased with the grain size. For the grain sizes of 3 μm and below, there was no severe loss of total elongation because of a large local elongation after the stress drop. Tensile strength was inversely dependent on the grain size and FSP increased the tensile strength of the cold-rolled 1050 aluminum alloy by 46% through the grain refinement. Hence, it is evident that FSP is very effective in enhancing hardness and tensile strength of materials through grain refinement.View full abstractDownload PDF (1014K) -
Jun-ichi Yamamoto, Yasuo Shimizu, Hajime Ohtani, Keisuke Shiozaki, Kaz ...2003 Volume 67 Issue 10 Pages 555-561
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSP-type and n-type α-FeSi2 produced by utilizing mechanical alloying (MA) process and spark plasma sintering (SPS) technique were heat-treated to transform their structure to the p-type and n-type β-FeSi2, respectively. Raw powders of iron(99.5%), silicon(99.9%), manganese(99.5%) and cobalt(99.9%) were mixed and mechanically alloyed for 72 ks using a planetary ball mill. Mixing fractions of the powders for preparing p-type and n-type α-FeSi2 were in accord with the mole fractions of the phases of Fe0.92Mn0.08Si2 and that of Fe0.98Co0.02Si2, respectively. The SPS process was carried out at 1293 K for 0.3 ks.
The power factor of the p-type β-FeSi2 heat-treated at 973∼1073 K for 7.2 ks was improved significantly as compared to that of the β-FeSi2 prepared by only the SPS process without heat treatment. Maximum power factor was measured to be 0.46 mW/mK2 at 850 K for the p-type β-FeSi2 heat-treated at 1073 K for 7.2 ks. The power factor of the n-type β-FeSi2 heat-treated either at 973∼1073 K for 3.6∼7.2 ks or at 1173 K for 1.8∼3.6 ks was improved as compared to that of the β-FeSi2 prepared by only the SPS process without heat treatment. Maximum power factor was measured to be 0.15 mW/mK2 at 650 K for the n-type β-FeSi2 heat-treated at 1073 K for 7.2 ks. However the maximum power factors obtained were not improved sufficiently, because the ε-FeSi phase partially existed in the specimen and also the p-type and n-type β-FeSi2 were contaminated with Fe, Cr and Ni originated from the MA pot and balls.View full abstractDownload PDF (1222K) -
Hakaru Nakato, Minoru Nitta, Ryoji Uchimura, Hirohumi Iinuma, Hiroshi ...2003 Volume 67 Issue 10 Pages 562-568
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSCharacteristics and pretreatment method for enrichment on silicon content of high purity silicon sludge filtrated from wastewater of silicon industry were investigated.
High purity silicon sludge consists of sub-micro fine particles and holding water with 15 to 40% in weight.
The content of oxygen in high purity silicon sludge is 2 to 10% and that of other impurities is extremely low.
Oxygen exists as silicon dioxide. It can be reduced to the level below 1% by hydrofluoric acid treatment or by reduction in solid state at elevated temperature over 1500 K in reduced atmosphere of 10−3-10−4 MPa.View full abstractDownload PDF (1073K) -
Kazuhiro Hanazawa, Noriyoshi Yuge, Shoichi Hiwasa, Yoshiei Kato2003 Volume 67 Issue 10 Pages 569-574
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe evaporation behavior of phosphorus in molten silicon has been investigated during electron beam irradiation to produce solar grade silicon (SOG-Si) from metallurgical grade silicon (MG-Si) by a sequential metallurgical process. The batch experiments showed that the evaporation rate of phosphorus increased in proportion to an increase of the power of irradiated electron beam and was found to be the first order with respect to phosphorus concentration. The removal rate of phosphorus was controlled by the free evaporation from the surface of molten silicon. The electron beam irradiation enables us to secure a higher temperature of free liquid surface, which results in efficient dephosphorization.
On the other hand, the continuous flow experiment indicated that the phosphorus concentration at the outlet increased because as the silicon feed rate was raised, the residual time of the molten silicon in the hearth was proportionately shortened. The flow of the molten silicon in the hearth did not behave with a complete mixed flow type reaction but close to a plug flow type reaction. With a 150 kg scale pilot manufacturing plant, MG-Si containing phosphorous of about 25 mass ppm was successfully purified to less than 0.1 mass ppm.View full abstractDownload PDF (496K) -
Noriyoshi Yuge, Kazuhiro Hanazawa, Shoichi Hiwasa, Yoshiei Kato2003 Volume 67 Issue 10 Pages 575-582
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSAs one of sequential purification processes where high purity silicon for solar grade silicon (SOG-Si) was manufactured by removing impurities from metallurgical grade silicon (MG-Si), a pyrometallurgical method to remove metallic impurities was developed in an industrial scale, utilizing segregation effect of metallic impurities during solidification.
The removal of metallic impurities from MG-Si was carried out with electron beam heating equipment. Molten silicon was supplied continuously at a constant mass to a mould made of water-cooled copper and was gradually solidified from the bottom to the upper direction. Iron concentration was presented by Pfann’s and Burton’s equations, and was removed from 1500 mass ppm of initial iron concentration to below 1 mass ppm. Aluminum was removed in excess, presumably because of vaporization to gas phase. We found that metallic impurities were not removed above a certain height of an ingot by partition during directional solidification and these phenomena depended on iron concentration condensed in the silicon pool. Mechanism for metallic impurity removals was estimated, on the basis of visual examination of structure and EPMA.
Iron concentration profile of ingot and critical height for purification were estimated, through experiments using a 20 kg scale, and were verified to be applicable to industrial scale experiments (150 kg scale). Solar grade silicon was made by way of trial with this process and it was verified to have satisfactory quality as a material for a solar cell.View full abstractDownload PDF (683K) -
Naomichi Nakamura, Hiroyuki Baba, Yasuhiko Sakaguchi, Shoichi Hiwasa, ...2003 Volume 67 Issue 10 Pages 583-589
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSBoron removal in molten silicon with a steam added plasma melting method was investigated as an important part of the sequential metallurgical process to produce highly purified solar grade silicon (SOG-Si) from commercially available metallurgical grade silicon (MG-Si). Experiments were carried out from laboratory to industrial scale and silicon amount used per charge was varied from 0.6 to 300 kg. Boron was stably removed to permissible boron content for SOG-Si of [B]<0.1 mass ppm. Deboronization rate was proportional to steam content, 3.23th power of hydrogen content in plasma gas, boron content in molten silicon and area of dimple formed by plasma gas jet, and inversely proportional to the mass of molten silicon. An application of the thermodynamics leads to preferential boron oxidation in molten silicon due to higher temperature, which showed that this plasma method capable of locally heightening the temperature of the reaction surface was advantageous in principle.View full abstractDownload PDF (572K) -
Tadashi Fukuda2003 Volume 67 Issue 10 Pages 590-594
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe effect of titanium on the toughness of 30% chromium ferritic steels was investigated by a Charpy impact test at low temperatures. Carbon content is (0.023±0.002) mass%, and titanium contents vary from 0.051 to 0.26 mass%. The ratio of titanium content to carbon content, Ti/C, ranges from 2.1 to 12.4. Two kinds of heat treatments with or without solution treatment were adopted to obtain different types of morphology of carbide precipitates.
The results obtained are summarized as follows:
(1) Aging after solution-treatment gives rise to grain boundary precipitation of coarse Cr carbides and numerous fine Ti carbides dependent of Ti/C ratio, while annealing without solution-treatment produces coarse globular carbide particles within the grains.
(2) Ductile-brittle transition temperatures (DBTTs) of the specimens containing grain boundary carbides are higher than those of the specimens containing carbide particles within the grains.
(3) In case of the morphology of grain boundary carbides, DBTT first decreased remarkably with increasing Ti/C ratio up to 5 and then increased with the ratio. While in case of the morphology of carbide particles within the grains, DBTT remained constant in a range of 2 to 8 of Ti/C ratio and then remarkably increased with the ratio.
(4) Initiation of microcracks for brittle fracture is considered to be caused by the intergranular fracture cracks which are brought about by the decohesion at the interfaces between the matrix and grain boundary carbide precipitates. Addition of excess titanium such as 12 of Ti/C ratio causes the increase of DBTT due to promoting brittle intergranular fracture and weakens the effect of morphology of titanium carbides on the DBTT.View full abstractDownload PDF (916K) -
Toshikazu Akahori, Mitsuo Niinomi, Tatsuya Higuchi, Koichi Morii2003 Volume 67 Issue 10 Pages 595-603
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSTi-Ni alloys show superior mechanical properties, especially fatigue strength as compared with other shape memory alloys, so that Ti-Ni alloys are used for practical applications. Ti-Ni alloys are mainly used as wires and plates for dental and medical applications under a cyclic load. Relationship between the shape memory characteristics and fatigue properties is important and should be understood to improve the safety usages of products made of Ti-Ni alloys. Recently, the third alloying elements have been attempted to add in Ti-Ni alloys, and the effects of the transformation temperature on the mechanical properties have been investigated due to achieve better mechanical properties. However, there are a few reports on the mechanical properties, in particular, fatigue strength with different Ni and third element contents. In present study, fatigue properties were investigated for Ti-54.2 mass%Ni, Ti-55.8 mass%Ni, Ti-55.4 mass%Ni-0.5 mass%Co and Ti-54.4 mass%Ni-1.49 mass%Co heat-treated at 723 K and 873 K for 3.6 ks followed by water quenching.
Transformation temperatures of Ti-Ni and Ti-Ni-Co alloys tend to decrease with increasing Ni contents and Co/Ni content ratio. Stress-strain curves of Ti-Ni and Ti-Ni-Co alloys show two-step deformation behavior except for Ti-54.4 mass%Ni-1.49 mass%Co. Fatigue ratio, which means the ratio of maximum cyclic stress to tensile strength, of Ti-Ni and Ti-Ni-Co alloys increases with increasing heat treatment temperature in low cycle fatigue (LCF) and high cycle fatigue (HCF) life regions except for Ti-55.4Ni-0.5Co. The fatigue ratio of Ti-54.4 mass%Ni-1.49 mass%Co heat-treated at 873 K shows the highest value in LCF and HCF life regions. The fatigue limit of Ti-54.4 mass%Ni-1.5 mass%Co is around 0.62. The reason for the increment of fatigue strength is that the transformation temperatures are much lower and the tensile strengths are relatively higher as compared with those of other Ti-Ni and Ti-Ni-Co alloys.View full abstractDownload PDF (1580K) -
Mitsuo Niinomi, Toshikazu Akahori, Tomohiro Yamaguchi, Toshihiro Kasug ...2003 Volume 67 Issue 10 Pages 604-613
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSAging characteristics and mechanical properties of biomedical β type titanium alloy, Ti-29Nb-13Ta-4.6Zr, coated with calcium phosphate invert glass-ceramic were investigated.
Vickers hardness values of cross sections of Ti-29Nb-13Ta-4.6Zr, TNTZ, prepared for dip-coating treatment, DCT, composed of a firing treatment, FT, at 1073 K for 0.9 ks or 3.6 ks followed by furnace cooling and conducted with only FT are almost the same, and are around 240 Hv. This value is much higher than that of TNTZ prepared for solution treatment, ST, at 1063 K for 3.6 ks. The increasing hardness is due to the precipitation of ω phases in the matrix, β phase, during FT. Tensile bonding strength of 5 μm thick coating layer of calcium phosphate invert glass-ceramic on TNTZ is not degraded by aging, but 20 μm thick coating layer is degraded. The modulus of elasticity of TNTZ prepared for DCT or aging after DCT is relatively higher than that of TNTZ prepared for ST, that is, around 80 GPa and 110 GPa, respectively.View full abstractDownload PDF (1507K) -
Sumiko Sanuki, Daiki Kaizawa, Hiroshi Majima2003 Volume 67 Issue 10 Pages 614-621
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSDecomposition of tartarate during the photocatalytic reduction of Cu(II)-tartarate complex alkaline solution whose pH was adjusted with NaOH was studied using TiO2 powders. The effects of various factors, such as concentrations of NaOH and potassium sodium tartarate, intensity of UV irradiation and identity of TiO2 powders, were investigated on decomposition rate of tartarate. The main findings obtained are as follows: In the concentration range of 0.1∼0.3 kmol·m−3 NaOH, both Cu(II) reduction and tartarate decomposition rates tend to linearly increase with the increase in NaOH concentration. As far as the same TiO2 catalyst was used, the adsorption amount of free tartarate ion as well as Cu(II)-tartarate complexes ions onto TiO2 catalyst increase with the increase in NaOH concentration, indicating that adsorption of these ions directly concerns to the photocatalytic reaction. The amount of tartarate decomposition was around 10% of Cu(II) reduction. We detected CO32− ions as the decomposed product, indicating a photocatalytic oxidation route of tartarate decomposition. Although the reduction rate of Cu(II) greatly decreased with the decrease in tartarare concentration, initial decomposition rates of tartarate were almost same despite of initial tartarate concentration. However, tartarate decomposition rates sharply increase near the termination of Cu(II) reduction reaction, showing more effective increase with the increase in initial tartarate concentration. By using different TiO2 catalysts, the amount of tartarate onto catalyst were affected by both surface area and adsorption activity of catalyst used. However, tartarate decomposition rate was not directly affected by the amount of tartarate adsorption in this case.View full abstractDownload PDF (611K) -
Long-Xian Ding, Keijiro Nakasa, Masahiko Kato, Jie-Ru Li2003 Volume 67 Issue 10 Pages 622-628
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSRadio frequency (R.F.) induction heating was applied to Ti, TiB2 and Cu mixed powder on a pure titanium substrate in vacuum. This method enabled the formation of a surface layer of TixCuy compounds (TiCu2 and Ti2Cu3) containing titanium di-boride (TiB2) particles. The layer with highest hardness (HV=8.0 GPa) and flat surface was obtained at a mixing ratio of Ti:TiB2:Cu=30:20:50(mol)%. The layer formation was completed in a shorter time by R.F. heating than normal electric furnace heating in vacuum. In case of R.F. heating up to 1170 K or 1220 K, TiB2 particles were distributed in lines in the TixCuy matrix, while TiB2 particles were homogenously distributed in case of electric furnace heating at 1223 K. Mixed powder initially melted at a temperature higher than 1170 K, and solidified by increasing the temperature to a higher value than 1240 K or with continuous holding at 1220 K. The reason for the solidification will be due to the decomposition of TiB2 and increase in melting point by the solution of boron into the melt.View full abstractDownload PDF (1365K)
- |<
- <
- 1
- >
- >|