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Volume 68, Issue 8
Displaying 1-24 of 24 articles from this issue
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Tsuyoshi Nishi, Hiroyuki Shibata, Hiromichi Ohta, Nobuyuki Nishiyama, ...2004 Volume 68 Issue 8 Pages 499-502
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe specific heat values of liquid Pd40Cu30Ni10P20, Pd40Ni40P20 and Pd40Cu40P20 alloys which are known to show excellent glass forming ability have been measured in the temperature range between 973 and 1123 K by the heat-flux type DSC with triple cells. The uncertainty of the specific heat values obtained with the DSC was estimated to be ±7% at most by measuring the specific heat of pure silver. The specific heat values for liquid Pd40Cu30Ni10P20, Pd40Ni40P20 and Pd40Cu40P20 alloys are given as follows. (unit: Cp: Jg-1K-1, T : K)
CpPd40Cu30Ni10P20 = −2.45×10-4T +0.739 973≤T ≤1123
CpPd40Ni40P20 = −2.53×10-4T +0.727 1023≤T ≤1123
CpPd40Cu40P20 = −4.18×10-4T +0.828 973≤T ≤1123View full abstractDownload PDF (373K) -
Takahide Kanameda, Takuji Okabe, Mitsuo Kido2004 Volume 68 Issue 8 Pages 503-506
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSMechanical alloying (MA) of powder mixtures of Ti-48 mol%Al was performed for various milling times by a planetary ball mill, and the MA powders were hot-pressed at relatively low heating temperatures of 673-873 K and pressures of 200-600 MPa. The influence of hot-press temperature and pressure on consolidation (densification, reactive synthesis, etc.) was investigated for the MA powders. In this experiment, some non-reactive Ti powders remained in the consolidated materials, but the optimum hot-press conditions for consolidation by reactive sintering are determined by the MA conditions (milling duration, etc.).View full abstractDownload PDF (1012K) -
Atsushi Sato, Yutaka Koizumi, Toshiharu Kobayashi, Tadaharu Yokokawa, ...2004 Volume 68 Issue 8 Pages 507-510
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSTo improve the high temperature strength, solid solution strengthening elements with amounts well above the solubility limit imposed by the solvus, have been added to high-strength Ni-base superalloys. Under long-term exposure at elevated temperatures, the formation of Tertiary phases causes a serious degradation in terms of creep strength. The Tertiary phases, also known as Topologically Close Packed (TCP) phases, and can be classified into μ, P, R, and σ types. Recently, it has been found that Platinum Group Metals (PGMs) elements are effective in controlling precipitation of TCP phases, although the exact mechanism of this phenomenon is not well understood.
This study was carried out based on a 3rd generation Ni-base superalloy, TMS-121, which contains 5 mass pct rhenium and is known to precipitate TCP phases; a series of alloys with different amount of ruthenium additions to TMS-121 were cast and heat treated in a variety of time and temperature conditions. Based on the microstructural examinations, Time Temperature Transformation (TTT) diagrams were constructed by heating the alloys at different aging time and temperatures. These diagrams indicated the critical amount of TCP phases that were known to deteriorate the high temperature strength. It was concluded that Ru addition is effective in stabilizing the microstructure by increasing the solubility of solid solution strengthening elements in Ni-base superalloys at high temperatures. It was also found that delaying the precipitation of TCP phases at all temperature ranges.View full abstractDownload PDF (1549K) -
Hajime Furuhata, Noriyuki Chikui, Osamu Ohashi2004 Volume 68 Issue 8 Pages 511-514
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe pulse electric current bonding (PECB) process, also called plasma activated sintering (PAS) or spark plasma sintering (SPS) by some researchers, has received much attention as one of the most advanced materials bonding processing in recent years.
In this work, we studied the effects of the initial electric current, which is the current in early bonding stage, on the bond quality (tensile strength, reduction of area, and bonded area ratio). The following results were obtained. When the initial electric current was high, local heating of the contact area was accelerated and the bond quality of the joints was better. However, initial current had the optimum value and it was necessary to choose the condition that the contact area at bonded interface does not melt locally. When the molten metal layer was formed on the contact area, it was migrated to the center of the bonding surface by the pinch effect. This phenomenon generated unhomogeneous heating of the bonding surface. Therefore, the bond quality of the joints was worse.View full abstractDownload PDF (4525K) -
Noriyuki Chikui, Hajime Furuhata, Norio Ymaguchi, Osamu Ohashi2004 Volume 68 Issue 8 Pages 515-518
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSDiffusion bonding process is one of solid state bonding processes that produces the joints by the application of pressure at elevated temperature without macroscopic deformation of the workpieces. For a conventional diffusion bonding technique, the joints are heated by the electrical resistance heaters, the induction high frequency heating and so on. Recently the pulse electric current bonding (PECB) process has received much attention as the advanced heating process at the bonding interface of joints.
To clarify the difference in the bonding quality by the heating processes, the joints of the SUS304 stainless steel were made using pulse electric current bonding and induction high frequency heat bonding (IHB). The results of fracture surface and tensile strength of the joints showed that the bonding temperature to form the metallic bond by PECB was lower about 100°C than that of IHB. The decrease in bonding temperature was attributed to the heating at bonding interface locally, depending on the Joule heating by the contact resistance.View full abstractDownload PDF (2881K) -
Noritaka Saito, Shinichi Shiota, Ayumu Umemoto, Kunihiko Nakashima2004 Volume 68 Issue 8 Pages 519-522
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe solubility of α-silicon nitride into RE2O3 (RE=Y, Gd, Nd and La)-MgO-SiO2 melts have been examined systematically. The effect of nitrogen content on the Vickers hardness of RE-Mg-Si-O-N oxynitride glasses have been examined.
The dissolution reaction of α-silicon nitride into melts have achieved equilibrium about 6 h holding at 1773 K. The content of saturated nitrogen was 4.8∼5.8 at%, depending on the ionic radius of adding rare-earth elements. A marked change was observed in the order of ionic radius from La to Y.
The Vickers hardness of RE-Mg-Si-O-N oxynitride glasses increased with increasing the content of nitrogen. The results from X-ray photo-electron spectroscopy of oxynitride glasses revealed the existence of Si≡N bonds. These results suggest that the substitution of nitrogen for oxygen may lead to the increase of cross-linking produces a more rigid glass network.View full abstractDownload PDF (383K) -
Kazuo Kobayashi, Koji Yamaguchi, Masao Hayakawa, Megumi Kimura, Toshio ...2004 Volume 68 Issue 8 Pages 523-525
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSHigh cycle fatigue properties of Alloy 718 for space use were investigated at temperature range from 77 to 873 K. The testing specimens were cut from welded joints as well as the base metals. The relationship between stress amplitude and fatigue life (S-N curve) had two steps for all the specimens at any temperatures, since the fracture mechanisms were different between low and high cycle regions. In low-cycle region, the origin of the fatigue fracture was the specimen surfaces, while in high-cycle region it was the facets inside or near the surface. And the fatigue strength depended on the austenitic grain size in high-cycle region. The facets, the origin of the fatigue fracture, corresponded to the grain size.View full abstractDownload PDF (1187K) -
Hitoshi Izuno, Tadaharu Yokokawa, Yutaka Koizumi, Satoko Odaka, Hirosh ...2004 Volume 68 Issue 8 Pages 526-529
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSWe proposed a new creep constructive equation to express the characteristic “S-shape” primary stage for Ni-base single crystal superalloys. In this report, parameters of the creep constructive equation for alloys of various compositions were analyzed by multi regression method, and the results were discussed in terms of the chemicel compositions and structural parameters of the alloys. The creep constructive curve was fitted to a creep curve at 1100°C, 137 MPa for each of 23 kinds of Ni-base superalloys. On the basis of the fitting results, multi regressions for each parameter were made with gamma-prime composition, lattice misfit and volume fraction of the gamma-prime phase as explanatory variables. This result enables the prediction of a creep curve of an alloy directly from its composition. Moreover, the effectiveness of alloying elements for the creep behaviours, especially during the primary stage, can be evaluated by the multi regression analysis.View full abstractDownload PDF (320K) -
Takamitsu Honjo, Kenichi Numazaki, Haru-Hisa Uchida, Yoshihito Matsumu ...2004 Volume 68 Issue 8 Pages 530-533
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSIn this study, the effect of the palladium surface treatment was investigated on the mechanical response of the LaNi5 thin film actuator deposited on polyimide substrates. Since controlling the hydrogen concentration in film by changing the pressure may reversibly drive this actuator, this film actuator can be expected as a sensor and/or a controller of hydrogen gas flux in various hydrogen-related devices. In the present experiments, it was shown that the initiating time for the actuation to be measured after hydrogen gas exposure was reduced from 100 s to 1 s by the palladium surface treatment. This significantly improved mechanical response was attributed to the switching of the reactions in the rate determining steps. The rate determining reaction after the palladium treatment was no longer the dissociation of hydrogen gas molecules on the sample surface, but the hydrogen permeation or diffusion in the film. Furthermore, it was found that the high responsiveness induced by the palladium treatment was also caused by the high permeability of hydrogen in palladium film at room temperature.View full abstractDownload PDF (1272K) -
Keisuke Iwata, Kunio Yamada, Atsushi Kadowaki, Naoki Yamaguchi, Akira ...2004 Volume 68 Issue 8 Pages 534-536
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSInfluences of electron beam irradiation on impact fracture energy were studied for soda glass. The irradiation, which was one of short-time treatments of dry process at low temperature below boiling point of water, increased the impact value of soda glass. The impact value enhancement can be explained by stress relaxation induced by increase in free volume related to dangling bonds.View full abstractDownload PDF (310K) -
Kazuya Oguri, Tatsuya Takahashi, Atsushi Kadowaki, Akira Tonegawa, Yos ...2004 Volume 68 Issue 8 Pages 537-539
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSAn effect of electron beam irradiation on mist resistance was studied for transparent polycarbonate resin. The electron beam irradiation decreased the time to clear vision on the misted samples. The treatment showed the mist resistance of the resin. To discuss the effect of electron beam on mist resistance, the water wettability, inducated by the surface energy, was evaluated by using contact angle of sessile drop. The electron beam enhanced the surface energy. Based on the heterogeneous nucleation theory, the effects of electron beam on the mist resistance were discussed.View full abstractDownload PDF (293K) -
Qinglian Zhang, Rongguang Wang, Masahiko Kato, Keijiro Nakasa2004 Volume 68 Issue 8 Pages 540-543
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe surface of SUS304 austenitic stainless steel was sputter-etched by Argon ions in a R.F. magnetron sputtering apparatus. The shape and chemical composition of precipitated carbides on the surface were examined by SEM, SIM, FIB and EPMA. Conical chromium carbides with an aspect ratio of about 2.8 between height and radius (radius: 0.1∼0.8 μm) protrudes from surface especially along grain boundaries. The precipitation and growth of such conical carbides is considered to be dependent on the surface temperature, gradient of temperature, numbers of introduced vacancies and diffusion coefficient of carbon. The aspect ratio of a conical carbide seems to be related to the growth rate of the carbide normal to sputter direction and the difference in sputtering rate between matrix and carbide.View full abstractDownload PDF (2085K) -
Tatsuya Hinoki2004 Volume 68 Issue 8 Pages 544-547
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSTungsten (W) and molybdenum (Mo) were coated on silicon carbide (SiC) as refractory armor using high power plasma arc lamp at powers up to 23.5 MW/m2. Both W powder and Mo powder were melted and formed coating layers on SiC. The effect of pretreatment (vapor deposition of titanium (Ti), W and Mo and annealing) and sample heating conditions on microstructure of the coating and coating/substrate interface were investigated. The microstructure was observed by scanning electron microscopy (SEM) and optical microscopy (OM). A strong W coating was successfully formed. Tungsten vapor deposition and pre-heating at 5.2 MW/m2 made for a refractory layer containing no cracks which propagated into the SiC substrate. This layer was formed without the thick reaction layers (WC and W5Si3) reported in previous studies. Moreover the thinner interface transition layer and armor avoid coefficient of thermal expansion (CTE) mismatch driven failure previously reported. For this study, small WC grains were observed adjacent to interface. Silicon carbide grains and W5Si3 grains were observed within W coating. By contrast, Mo was not formed as well as W due to larger CTE mismatch than that for W and SiC.View full abstractDownload PDF (2413K) -
Michihisa Fukumoto, Ryou Matsui, Motoi Hara, Toshio Narita2004 Volume 68 Issue 8 Pages 548-551
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe coating of a Ni aluminide layer on a Nb substrate was carried out by the electrodeposition of Ni and Al. The improvement of the high-temperature oxidation resistance for Nb was then evaluated. Ni and Al were deposited by aqueous solution and molten salt electrolysis, respectively. The thickness of the deposited layer increased with time for the nickel electrodeposition. When the nickel electrodeposition time is short, NiAl3 and Ni2Al3 are formed as the outer and inner layers, respectively. When the nickel electrodeposition time becomes longer, on the other hand, Ni2Al3 and Ni are formed as the outer and inner layers, respectively. The oxidation resistance of Nb was improved by coating of the Ni-aluminum intermetallic compound. Especially, a Nb specimen covered with a coating layer consisting of Ni2Al3 and Ni as the outer and inner layers, respectively, showed an improved oxidation resistance during the prolonged oxidation test.View full abstractDownload PDF (4654K) -
Yuichiro Miura, Saori Yokota, Yu Fukai, Tohru Watanabe2004 Volume 68 Issue 8 Pages 552-557
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSEfficts of hydrogen on the structure of electrodeposited Cr film have been investigated by combining the X-ray diffractin and thirmal desorption spectroscopy, by systematically varying the plating conditions. A large amount of hydrogen can be dissolved at high current densities in a Cr rich bath at low temperatures, and causes transformation with increasing hydrogen concentrations into hcp and fcc hydredes. Hydrogen dissolved in hcp and fcc lattices desorbs at ∼100°C, but a certain fraction remains as bubbles and evolves at >800°C by inhomogeneous processes leaving craters on the surface.View full abstractDownload PDF (5698K) -
Masakazu Kobayashi, Masanori Kobori, Yoshimasa Takayama, Hajime Kato2004 Volume 68 Issue 8 Pages 558-564
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe continuous cyclic bending (CCB) and subsequent annealing made it possible to produce the gradient microstructure with the coarse-grained surface and the fine-grained central layers in an Al-Mg-Mn alloy sheet. The microstructural evolution during annealing in the continuous cyclic bent (CCBent) sheet was simulated by Monte Carlo (MC) simulation of recrystallization in order to investigate an effect of working and annealing conditions on thickness fraction of coarse-grained layer in this study. Further, we attempted to reproduce the thickness fraction of coarse-grained layers that reported by the experiment in the Al-Mg-Mn alloy sheets by the MC simulation.View full abstractDownload PDF (4968K) -
Kenichi Nakajima, Yohji Uchiyama, Kohmei Halada2004 Volume 68 Issue 8 Pages 565-567
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSAccording to increase in a waste scrap, a process is noticed in which a waste scraps is consumed for sheet steel production within severe restriction of impurities concentration. In this study, evaluation of the effect on environmental load decline by LCA is applied to this new recycling technology.
Target of this study is not for closed loop recycling system like aluminum can for drink but for open loop recycling system in which many industries are concerned. Authors suggest taking the interindustry-relations table for open loop recycling system. Evaluation made in this research is based on it. By setting up I/O boundary, though increase of environmental load is predicted to be high comparing to those which are assumed as non-open recycling system, still there is a sufficient effect for it. As the result of the analysis, curtailment was estimated that energy consumption and CO2 emission are 16.8 GJ per ton waste scrap and 1.2 t per ton waste scrap, respectively.View full abstractDownload PDF (311K) -
Takeshi Fujita, Nobuyuki Nakamura, Toshiaki Urabe, Kaneharu Okuda, Yos ...2004 Volume 68 Issue 8 Pages 568-576
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe effect of the microstructure prior to cold rolling on the recrystallization texture and planar anisotropy of the r -value (Δr) in JIS S35C cold-rolled high carbon steel sheet were investigated.
When the structure contains fine spheroidized cementite prior to cold rolling, recrystallization is retarded and takes the form of in-situ recrystallization. However, with coarse cementite, recrystallization is completed at a low temperature, and in subsequent grain growth, Ostwald growth of cementite is rate-governing. This difference in recrystallization behavior is inferred to be caused by differences in both the size and the distribution of cementite. Δr in smaller with fine spheroidized cementite than with coarse spheroidized cementites. This is thought to be caused by both the strong development of γ-fiber (‹111›//ND) grains in the recrystallization texture and retardation of {110} grains, which reduce Δr, during annealing. Therefore, it is inferred that refinement of cementite prior to cold rolling contributes to the improvement of the recrystallization texture as it affects Δr.View full abstractDownload PDF (14047K) -
Tadaharu Yokokawa, Makoto Osawa, Yutaka Koizumi, Toshiharu Kobayashi, ...2004 Volume 68 Issue 8 Pages 577-581
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSIn order to design for the Ruthenium (Ru)-bearing nickel-base superalloys, a series of phase estimation equations for γ and γ′ phases in Ru-bearing nickel-base superalloys were established by regression analysis of data obtained by the electron-probe X-ray micro-analysis (EPMA). The partitioning ratios of alloying elements in Ru-bearing superalloys, and their temperature dependencies were experimentally obtained. The prediction equations for the partitioning ratios of alloying elements, and for the aluminum content in γ′ phase at arbitrary temperatures were developed. By using these equations and the lever rule of chemical compositions for the γ and γ′ phases, the compositions and volume fractions of γ and γ′ phases in equilibrium for Ru-bearing Ni-base superalloys were successfully estimated for various alloy compositions and temperatures. The estimated compositions and volume fractions of γ and γ′ phases showed a good agreement with the values obtained from EPMA and X-ray analysis.View full abstractDownload PDF (366K) -
Kazunori Asano, Hiroyuki Yoneda2004 Volume 68 Issue 8 Pages 582-590
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSAluminum alloy matrix hybrid composites reinforced with particle-attached continuous alumina fibers were fabricated by squeeze casting, and the effects of the particle-dispersion on their strength in the temperature range 293 to 623 K were investigated by microscopy and fractography. It was found that the particle-dispersion among the fibers minimizes the preform contraction and fiber-to-fiber contact due to melt infiltration during the squeeze casting, resulting in a homogeneous distribution of the fibers in the composite. The tensile strength, 0.2% proof stress and elastic modulus of the composites in the longitudinal direction increased due to the particle-dispersion over the whole temperature range measured. The fracture surface of the particle-free composite was flat and close-packed fibers were frequently observed, indicating that stress concentrated in the neighboring fiber, then the cracks initiated at the points of fiber contact, followed by progressive fracture of the touching fibers. In contrast, the surface of the hybrid composite was irregular and close-packed fibers were rarely observed, showing that the matrix around a fiber relieved the stress concentration and the strengthening by the fibers was satisfactory. The transverse tensile strength and proof stress of the particle-free composite were lower than that of the unreinforced alloy. Many fibers and grooves remaining in the matrix were observed on its fracture surface. This is considered to be due to the initiation of the cracks at the points of fiber contact and their propagation mainly along the fiber-matrix interface. In contrast, the strength of the hybrid composite was close to that of the unreinforced alloy. The matrix was dominant on its fracture surface. This is attributed to the strong fiber-matrix interface and the propagation of cracks mainly throughout the matrix.View full abstractDownload PDF (16906K) -
Yuji Nagae2004 Volume 68 Issue 8 Pages 591-595
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSIt has been found that the magnetic property changes in austenitic stainless steel subjected to creep. The change of magnetic property is mainly caused by the transform into martensite. In order to investigate the magnetism of Fe-Cr-Ni ternary alloy with face-centered cubic besides the martensite, the spin configuration is evaluated by DV-Xα cluster method. The spin configurations of γFe, γFe-Cr, γFe-Ni and γFe with vacancy are calculated. The effect of lattice constant on spin configuration is also evaluated. The γFe with normal lattice constant has an antiferromagnetism. But the γFe with lattice constant of around 0.37 nm has a ferromagnetic property. The γFe with a vacancy has a ferromagnetic property even in the normal lattice constant of γFe. The magnetic property between Fe atom and Ni atom is always ferromagnetism in the range of calculated lattice constant. On the other hand, the magnetic property between Fe atom and Cr atom is always antiferromagnetism in the range of calculated lattice constant. It is possible to transform into ferromagnetism in the case of existence of many vacancies or of increase in lattice constant for face-centered cubic structure.View full abstractDownload PDF (288K) -
Long-Xian Ding, Masahiko Kato, Keijiro Nakasa, Taiga Inoue2004 Volume 68 Issue 8 Pages 596-604
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSMixtures of Ti, Ni and TiB2, TiC or SiC powders were spark- and resistance-sintered to obtain TiB2, TiC or SiC dispersed TiNi pseudoelastic alloy. The alloys were annealed, solution treated and aged after the sintering. Nano-indentation tests, bending tests, and abrasion wear tests were carried out on these alloys. Nano-indentation tests showed that the TiNi alloy and ceramics-dispersed TiNi alloys exhibited larger displacement recovery than the reference materials such as steels and titanium alloy at the same indentation displacement. The solution treated and aged specimens exhibited larger displacement recovery than the annealed ones. Vickers hardness of the annealed alloys increased with increasing ceramics content, while relative density and bending strength decreased. TiB2 dispersed TiNi alloy has higher hardness than TiC dispersed TiNi alloy and larger bending strength than SiC added alloy. Abrasive wear resistance of TiB2 dispersed TiNi alloy was much larger than that of the steels and titanium alloys, which can be explained by the stress relaxation of pseudoelastic matrix surrounding ceramics particles. In addition, the TiNi alloys annealed after sintering exhibited better wear resistance than the solution treated and aged ones. The wear resistance of TiB2 dispersed TiNi alloy was larger than that of TiC dispersed TiNi alloy perhaps because of larger interfacial strength between TiB2 particles and TiNi matrix than that of TiC particles and TiNi matrix.View full abstractDownload PDF (13977K) -
Osami Seri, Fumiaki Hirose2004 Volume 68 Issue 8 Pages 605-610
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSWe have shown that the Al-Fe-Si intermetallic compound particles exposed on 1100 aluminum wrought alloy (industrially pure aluminum alloy) are preferentially and selectively removed by two steps: the first step is selective dissolution of aluminum component in the Al-Fe-Si intermetallic compound by electrochemical reaction. The second step is intensive removal of the iron-enriched intermetallic particles on which vigorous hydrogen bubbling has been took place, which is accelerated by application of ultrasonic vibration. It is found that the intermetallic compound-free surface obtained by the proposed technique is preferable for the surface treatment such as Ni-P electroless plating.View full abstractDownload PDF (10826K) -
Koji Kakehi, Satoru Takahashi2004 Volume 68 Issue 8 Pages 611-614
Published: 2004
Released on J-STAGE: June 24, 2005
JOURNAL FREE ACCESSThe creep strength of single crystals of Ni-base superalloys has been interpreted in terms of the Schmid factors and multiplicity of {111} ‹112› type slip systems in the intermediate temperature ranges. {111} ‹112› type slip greatly decreases creep rupture life even in the third generation alloys which contain Rhenium by strain softening. Therefore, it is very important to investigate strain softening behavior of Ni-based superalloys to put advanced superalloys to practical application. The purpose of the present investigation is to study the strain softening in the creep deformation and to understand the resultant changes of creep behaviors on each orientation. It was found that strain softening was occurred by ‹112› viscous slip and deformation twinning in the [001] and [011] orientations, respectively, and that there was incubation period prior to strain softening. In the [111] creep, strain softening was not observed because it is very difficult for dislocations to cut the precipitates.View full abstractDownload PDF (556K)
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