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Volume 35, Issue 4
Displaying 1-19 of 19 articles from this issue
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Tsugio Ogura, Seiichi Karashima1971 Volume 35 Issue 4 Pages 291-299
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSBased on the results obtained by a series of X-ray and transmission electron microscope studies on the structure near fatigue cracks, a vacancy absorption model is proposed for the propagation of a fatigue crack. In the course of stress cycling, a great number of vacancies are generated in the plastic zone and in the stress-concentrated region around a fatigue crack. Those vacancies diffuse towards a region near the tip of the fatigue crack due to the compressive stress gradient at the crack tip. It appears that the growth of a fatigue crack occurs as a result of the absorption of the vacancies.
The migration rate of vacancies in a field of stress gradient and the total volume of vacancies absorbed by a fatigue crack in one stress cycle was calculated to give an equation for the propagation rate of a fatigue crack. Comparison of the propagation rates calculated from the above equation with those obtained experimentally leads to the following conclusions. The short circuit migration of vacancies along dislocations should be taken into account to discuss the fatigue crack propagation. The stress intensity factor and the frequency of stress cycling would have an important effect upon the vacancy mechanism mentioned above.View full abstractDownload PDF (2549K) -
Haruoki Maeda, Akikazu Nakagiri, Ikuo Yoshida1971 Volume 35 Issue 4 Pages 299-307
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSWhen an ultrasonic is applied during wire drawing, the decrease of drawing stress is observed. From a study of comparison of the draw-bench apparatus with the bull-block apparatus, it has been comfirmed that the decrease of drawing stress is steadily dropped by the latter apparatus. Then, using the bull-block apparatus, the relation ships of the drawing stress with the percentage of reduction, amplitude of applied ultrasonic and drawing speed have been investigated in details. The following results are obtained.
(1) When the drawing speed is increased, no effect of ultrasonic on the drawing stress is observed. The relation between the limit of drawing speed vt,l and maximum wave velocity vf,max is expressed as vf,max×(1⁄π)=vt,l.
(2) The effect of amplitude on the decrease of the drawing stress is examined with SUS 24 and SUS 27, respectively. In SUS 24, the decreasing ratio of the drawing stress varies at the amplitude of 4 micron, but in SUS 27, it varies linearly with the amplitude.
(3) When the ultrasonic drawing is superimposed upon the usual one, the wire indicates the effect of ultrasonic cleaning which improves the wettability between the wire and the lubricant, and the drawing stress decreases independently of the amplitude.
(4) The decrease of the drawing stress by ultrasonic does not depend on the reduction of cold working.
(5) Up to the reduction of 89% in continuous drawing, the drawing stress and the relative drawing stress show different behaviors at 66% reduction.View full abstractDownload PDF (2507K) -
Haruoki Maeda, Akikazu Nakagiri, Ikuo Yoshida1971 Volume 35 Issue 4 Pages 308-313
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSInvestigation has been made on the mechanical properties and some structures of the wires made by the ultrasonic drawing and usual drawing. The following results are obtained.
When the drawing speed is less than 1⁄π of that of the vibrational speed, that is, the vibration of ultrasonic is considered to be sufficiently effective, the tensile strength of the wire is decreased and the elongation is increased.
The change of the tensile strength by continuous drawing in reduction from 57 to 66% shifts to a lower reduction percentage by ultrasonic vibration. Further, by more than 82% reduction, work softening is promoted by ultrasonic.View full abstractDownload PDF (1858K) -
Mitsuo Kurachi, Takeo Kudo1971 Volume 35 Issue 4 Pages 313-319
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe electrodeposition of γ-manganese from a sulphate bath containing 150 g/L of (NH4)2SO4 and 40 g/L of Mn++ was performed. The transformations of the γ-manganese to α-manganese were studied by means of measurements of the deflection of the deposit with a contractometer and of the change in the magnetic susceptibility of the deposit. X-ray observations were made to check the relation between the deflection of the deposit and the change in crystal structures of the deposit. The results obtained are summarized as follows:
(1) Change of the contractile deflection of the electrodeposited γ-manganese on being exposed in air corresponds closely to the transformation from γ-to α-manganese. The rate of the transformation was estimated from the results of the deflection measurements, and the activation energy of the transformation obtained is 22.3 kcal/mol.
(2) The magnetic susceptibility of the γ-manganese is found to be 7.15×10−6 e.m.u./g and that of the α-manganese transformed from electrodeposited γ-manganese is 9.67×10−6 e.m.u./g. The rate of the transformation was obtained from the measurements of magnetic susceptibility, and the activation energy of the transformation was estimated to be 21.4 kcal/mol, which is close to 21.2 kcal/mol obtained from the measurement of electric resistivity during the transformation by Potter et al.
(3) The rates and activation energies of the transformations in the γ-manganese and the mixture of γ-and α-manganese electrodeposited from the baths containing a small amount of Na2SeO4 are almost the same as those of the γ-manganese electrodeposited from the bath without Na2SeO4.
(4) The results of deflection, magnetic susceptibility and X-ray measurements do not show the presence of β-manganese at any stages of the transformation and it may be concluded that β-manganese is not formed as an intermediate product during the transformation from γ to α.View full abstractDownload PDF (2019K) -
Yoshiyuki Mizutani, Tomoji Ishiguro, Koichi Nakajima1971 Volume 35 Issue 4 Pages 319-323
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe surface deterioration of Fe-C alloys due to ultrasonic-induced cavitation in water at 25°C was examined by using X-ray technique and electron microscopy.
It was found from these results that (1) a large change of the structure was observed during the incubation time for cavitation erosion, depending on the way of heat treatments, (2) cavitation attacked preferentially a specific phase in the materials, e.g. α-ferrite in pearlite and (3) hardening of the surface layer due to erosion increased with the progress of surface damage.View full abstractDownload PDF (1210K) -
Hisashi Izumi, Hisakichi Sunada, Gunji Shinoda1971 Volume 35 Issue 4 Pages 324-330
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe present work was carried out so as to investigate the change in fatigue strength by pre-working, welding of stainless steel which has two phases, austenite and ferrite. The fatigue test was done by pulsating tension and the structural changes associated with the fatigue were also examined by means of X-ray, electron-microscopy and EPMA.
The results obtained are summarized as follows:
(1) The fatigue strength of austenitic-ferritic stainless steel was considerably stronger than that of austenitic stainless steel and that a difinite fatigue limit was obtained similary with carbon steel by means of age-hardening of ferrite during the fatigue test. The influence of martensitic transformation by pre-working on the fatigue strength was negligibly small.
(2) In the γ-phase Cr was lower than Ni, while in the α-phase Ni was rather lower. The variation of composition by welding was considerably violent in the heat affected zone.
(3) This alloy was not sensitive to a mechanical or welding notch. The decrease of fatigue strength was due largely to the change of composition and structure by welding heat.
(4) The change of fatigue strength of this alloy was little by welding. Moreover the solution-treatment temperature of about 1100°C after welding was deemed adequate.
(5) As stainless steel with two phases was relatively unstable in structure, a complicated striation pattern was obseved in the fatigue fractured surface.View full abstractDownload PDF (2307K) -
Etsujirô Yajima, Tôru Miyazaki, Takuo Itô, Masaaki M ...1971 Volume 35 Issue 4 Pages 331-338
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe present work deals with structural change during aging for Fe-W-Co alloys containing additional elements, Cr and V.
The results obtained are as follows:
(1) The super-saturated solid solutions of the alloys were decomposed into two phases; W-rich and W-poor zones in the early stages of aging. Age-hardening of the alloys is mainly due to this structural modulation. The W-rich zone transforms to a meta-stable intermetallic fct η′-phase continuously and finally to a stable precipitate, (FeCo)7W6. In the W-poor zone the superlattice of FeCo or Fe3Co may be formed, and the superlattice gives some influence on the age-hardening.
(2) The wave length and the amplitude of the modulated structure during aging increase very slowly. The fact that the softening rate of the alloys during over-aging is very small may be due to the small growth rate of the modulated structure.
The activation energy for the growth of the wave length in the modulated structure is nearly equal to an energy for volume diffusion of W atoms in alpha iron. Therefore, this suggests that the growth of the modulated structure is controlled by the diffusion rate of W atoms.View full abstractDownload PDF (2325K) -
Genjiro Mima, Yasuzo Tanaka1971 Volume 35 Issue 4 Pages 339-344
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe grain size dependence of yield stress and flow stress in the quenched and aged Mg-3%Zn alloy was studied by the tensile test and the electron microscopic observation in the temperature range from room temperature to −195°C. The main results obtained are as follows:
(1) This alloy does not clearly show the yield point in the stress-strain curves and parabolically hardens irrespective of grain size and aging treatment.
(2) The change in the yield stress or flow stress with grain size obeys the Hall-Petch relationship. This relation holds good for the precipitated alloy.
(3) ky shows a large temperature dependence, and its value of the age-hardened alloys is twice greater than that of the precipitate free alloys in the whole temperature range.
(4) The strain dependence of k is not so large in the precipitate free alloys, but it is large in the age-hardened alloys. The value of k in the age-hardened alloy is the largest at about 1% strain.
(5) It seems that the value of ky serves as a measure of the facility of prismatic slip.
(6) In the temperature range from room temperature to −195°C, the friction stress σ0 obtained from the above relation varies from 7 to 1.5 kg/mm2 in the precipitate free state, from 6.5 to 4.5 kg/mm2 in the age-hardened state.View full abstractDownload PDF (1619K) -
Genjiro Mima, Yasuzo Tanaka1971 Volume 35 Issue 4 Pages 345-350
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe room-temperature strength of Mg-4 wt%Zn polycrystalline (grain size, about 50 μ) alloys at various aging stages was studied by the tensile test and electron microscopic observation. It was found that this alloy is age-hardened by the following mechanisms.
(1) The yield strength in the early stages of aging (pre-β′) is determined by the increase of the energy which is required to make an interface dislocation between particles and the matrix due to the cutting of particles by dislocations.
(2) The yield strength in the middle of aging (β′+β) is determined by the increase in energy of Mg·Zn pairs, which are put out of order by dislocations passing through the particles.
(3) The yield strength in the stage of over-aging is due to the by-pass of dislocations on the basis of Orowan’s mechanism.
(4) The work hardening in this alloy is explained by Ashby’s theory of secondary slip.View full abstractDownload PDF (1356K) -
Shigeo Zaima, Masanori Muso1971 Volume 35 Issue 4 Pages 350-357
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAluminium binary alloys were prepared into plates with 0.34∼19.8% magnesium, highly soluble in aluminium; with 0.03∼3.00% manganese, slightly soluble in aluminium; and with 0.53∼2.30% iron, almost insoluble in aluminium. Low-speed orthogonal cutting was abruptly stopped and the built-up edge formed around the tool tip was observed. In this experiment, typical nose type built-up edges were recognized in Al-Mg alloys and Al-(2.70∼3.00%)Mn alloys, and plate type built-up edges were observed in Al-Fe alloys and Al-(0.03∼1.12%)Mn alloys.
In the case of nose type built-up edges, the faster the cutting speed or the smaller the rake angle, the larger the figure of built-up edge. In the case of Mg addition, the alloy containing 8.19%Mg showed the largest built-up edge. The shape of the built-up edge was in substantial agreement with Hoshi’s form, y=(1⁄4t)x2 (where x: horizontal length of the built-up edge, y: vertical length of the built-up edge and t: depth of the cut), except the cases of very low cutting speed and small rake angle. In the growing stage of the built-up edge, the cutting resistance showed overrunning and the cut surface was deteriorated. However, as the built-up edge became stabilized, the cutting resistance decreased in some measure and showed a stationary state, resulting in improvement of the cut surface which is called “the cutting transient phenomena”.
In the case of plate type built-up edges, the built-up edge grew of a certain size adhered on the tool surface in the early cutting stage and no remarkable change was caused by the progression of cutting, thus indicating little variation in cutting resistance. But, as the plate type built-up edge grew, the cut surface became deteriorated with the rise of cutting speed.View full abstractDownload PDF (1339K) -
Tadayuki Nakayama, Yoshiki Oshida1971 Volume 35 Issue 4 Pages 358-363
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSEffects of Si concentration and surface polishing conditions on the structures and chemical compositions of the initial oxide films formed on 18-8 and 18Cr stainless steels in high temperature water were investigated by means of electron microscopy, transmission electron diffraction and X-ray microanalysis.
Main results obtained are as follows:
(1) Polishing conditions had effects on structures and compositions of oxide films produced on low-Si containing 18-8 stainless steel (0.02 wt%Si); namely corundum type oxides formed on the mechanically polished surface consisted of Fe and Cr, but spinel type oxides produced on the chemically (or electrolytically) polished surface consisted of Fe, Cr and Ni.
(2) The spinel type oxides, on the contrary, were formed on three differently polished surfaces of 18-8 stainless steels bearing 2.29 wt%Si. However, chemical compositions of these spinel type oxides were affected by the polishing conditions; Fe, Cr and Si were detected from the oxides formed on the mechanically polished surface, while the oxides produced on the electrolytically (or chemically) polished surface consisted of Fe, Cr, Ni and Si.
(3) No effects of polishing conditions were noticed on structures and chemical compositions of the oxide films formed on variously polished surfaces of the both low-Si (0.17 wt%Si) and high-Si (2.24 wt%Si) containing 18Cr stainless steels. The corundum type oxides consisting of Fe and Cr were formed on 18Cr-0.17Si stainless steels and spinel type oxides of Fe and Cr with amorphous silicon oxides were produced on 18Cr-2.24Si stainless steels.
(4) For both 18-8 and 18Cr stainless steels, the corundum type oxides formed in high temperature water changed to the spinel type oxides with increasing Si concentration.View full abstractDownload PDF (1455K) -
Kazuhiko Asano, Ken-ichi Hirano1971 Volume 35 Issue 4 Pages 364-371
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSReversion characteristics in an aluminium-4% copper alloy has been investigated by means of electrical resistivity measurement and tensile tests. Electric resistivity is decreased by the reversion heat-treatments if it is higher than the value of the as-quenched specimen before reversion, and vice versa. The strength, on the other hand, is decreased monotonically by the treatments. It has been concluded that the resolution of the G.P. zones is responsible for these changes.
It has been found that the minimum temperature, TGP, is necessary for complete reversion and that the longer is the ageing time and the higher is the ageing temperature, the higher is TGP. These characteristics are successfully explained in terms of the stability of the G.P. zones. It can be also shown that rather complicated reversion phenomena in the literatures are fully interpreted by considering the change in the stability of the G.P.zones with the ageing time and temperature. It has been found that the possible highest ageing temperature to form the G.P.zones is as high as 275°C.
The diffusion processes during the reversion have been discussed and it has been shown that the reversion is rate-controlled by the diffusion of copper atoms in the matrix. The activation energy of the reversion after the excess vacancies are annealed-out has been determined to be about 30 kcal/mol.View full abstractDownload PDF (2819K) -
Atsushi Oguchi, Susumu Yoshida, Minoru Nobuki1971 Volume 35 Issue 4 Pages 371-377
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe influence of high hydrostatic pressure on the flow stress of zinc and zirconium polycrystals has been investigated at room temperature. Pressurizing under a pressure of 12000 kg/cm2, tensile tests using the differential pressure method between atmospheric pressure and 12000 kg/cm2, and tensile tests under a constant hydrostatic pressure of 12000 kg/cm2 have been carried out. The tensile load has been measured by a magnetostrictive load cell in the high pressure chamber. The results obtained are as follows: (1) Both the materials belong to the hexagonal close-packed system and are anisotropic in their elastic constants. Therefore, it is expected that shear stresses are generated at grain boundaries when they are subjected to high hydrostatic pressure and cause the pressurizing effect. The effect of pressurizing, however, is very small and is within the error of measurement for both the materials at atmospheric pressure. It seems that for zinc the most part of work-hardening caused by pressurizing disappears rapidly due to recovery before tensile testing and for zirconium the shear strain due to pressurizing remains in the elastic region. But it is presumed that a pressurizing effect will remain latently under high hydrostatic pressure if the annealed material is not returned to atmospheric pressure after being pressurized. (2) In the differential pressure method, the change of flow stress with the ambient pressure includes the latent pressurizing effect. At large strains where the latent pressurizing effect decreases and becomes negligibly small, the rate of change of flow stress between 12000 kg/cm2 and atmospheric pressure is shown to be about 8% for zinc and about 3% for zirconium. These values coincide with the rates of change of shear modulus of the materials by hydrostatic pressure which are estimated theoretically. (3) The work-hardening is enhanced for these materials under hydrostatic pressure. In the case of zirconium, the tendency of enhancement is similar to that observed with cubic metals. That is, at first it increases and then becomes saturated. For zinc, the enhancement continues to increase with increasing strain in the strain range tested. This seems to be due to the fact that recovery is suppressed under hydrostatic pressure, while it takes place actively at atmospheric pressure.View full abstractDownload PDF (2194K) -
Shitoshi Ôtani, Minoru Nishigaki, Shoichi Tokuda1971 Volume 35 Issue 4 Pages 378-382
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTwo anomalys in the tensile properties at elevated temperatures were observed in the Ti-Mo base metastable beta titanium alloys annealed in the beta field. The one is the existence of a peak on the flow stress-temperature curve in the vicinity of 400°C and the other is the existence of a serration on load-elongation curve in the range of 200° to 400°C. With the objective of procuring more detailed information for these two anomalys, the tensile tests at elevated temperatures were carried out on metastable beta titanium alloys of different stability such as Ti-12Mo-6Sn, Ti-11.5Mo-6Zr-4.5Sn, Ti-15Mo-0.2Pd, Ti-15Mo-5Zr, Ti-15Mo-5Zr-3Al, Ti-15Mo-5Zr-3Al-2V, and Ti-13V-11Cr-3Al. At the same time the effect of strain rates and annealing conditions on these two anomalys were examined. From the results it becomes evident that these two anomalys are not observed in a rather stable beta alloy, Ti-13V-11Cr-3Al, and Ti-15Mo-5Zr, prestabilized by annealing at 400°C or 500°C for 8 hr before tensile testing. The new type of serration observed in this study is different from the one due to the Portevin-Le Chatelier effect which has been suggested for mild steel and aluminium alloys.
It is concluded from this investigation that both the peak of flow stress at 400°C and the serration on the load-elongation curve in metastable beta titanium alloys are due to the transformation of the metastable beta to the omega phase which took place during deformation.View full abstractDownload PDF (1199K) -
Kimio Itagaki, Akira Yazawa1971 Volume 35 Issue 4 Pages 383-389
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSUsing the adiabatic calorimeter, heats of mixing in the binary liquid alloys consisting of copper and silver, gold, aluminum, gallium, indium, germanium or tin were determined at 1100°C. The experimental data obtained were represented by the following ξ function:
(This article is not displayable. Please see full text pdf.)
The main results obtained are as follows.
(1) The behaviors of heats of mixing and some systematic correlations between heats of mixing and positions of the considered couples on the periodic table in the copper alloys are similar to those in the silver alloys.
(2) The heats of mixing in the copper alloys are closely related to the phase diagrams, suggesting that the atomic bonding in the solid copper alloys are retained partly in the liquid alloys.
(3) Since the ξ function of copper alloys having secondary solid solutions in solid phase decreases markedly with increasing copper concentration, it is considered that the interaction energy depends considerably on copper concentration.
This dependence seems to be explained well by Engel’s hypotheses for the electron distribution in copper and its alloys.View full abstractDownload PDF (2132K) -
Kimio Itagaki, Akira Yazawa1971 Volume 35 Issue 4 Pages 389-394
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSUsing the adiabatic calorimeter, heats of mixing in the binary liquid alloys consisting of gold and silver, aluminum, gallium, indium, germanium or tin were determined at 1100°C.
The experimental results obtained were discussed in a similar way described in the previous paper.
The main results obtained are as follows:
(1) Some systematic correlations were found between heats of mixing in the gold alloys and positions of the considered couples on the periodic table, but the correlation in a given group is quite different from that in the silver or copper alloys.
(2) The ξ function of the gold alloys having compounds in a solid phase shows a linear dependence on the gold concentration like that in subregular solution. This behavior is different from that of the silver or copper alloys, in which ξ shows a markedly negative value in the silver or copper rich region, owing to the larger electronegativity factor in the gold alloys.View full abstractDownload PDF (1592K) -
Eisuke Iguchi, Kazuo Yajima1971 Volume 35 Issue 4 Pages 395-401
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe single crystal rutile in the form of slices was reduced in vacuum. The reduction was performed in three kinds of vacuum atmospheres, (A) vacuum by a diffusion pump without traps, (B) vacuum by a diffusion pump with liquid nitrogen traps and (C) vacuum by an ion pump. The process of reduction is considered to represent the process of diffusion of point defects induced by reduction. The diffusion coefficients of point defects in the reduced rutile were determined by the theory of the diffusion in a plane sheet with an equal surface concentration and the uniform initial distribution of solute in the sheet. These coefficients obtained in vacuum by the diffusion pump varied with the reduction time and this tendency was more remarkable in the case of the diffusion pump without traps. But the diffusion coefficients obtained in vacuum by the use of the ion pump were nearly constant at any reduction temperature independent of the reduction time except the beginning. It seems that these differences are due to the contamination by the diffusion pump. It becomes evident that specimens reduced with the diffusion pump are influenced by contamination by the diffusion pump oil. For the investigation of the reduced rutile, therefore, the ion pump should be used instead of the diffusion pump. By using the ion pump, the diffusion equation of point defects in the reduced rutile can be expressed as
(This article is not displayable. Please see full text pdf.)
This activation energy is very close in value to that of the oxygen vacancy in rutile.View full abstractDownload PDF (2121K) -
Michio Yamashita, Hiroshi Tomono, Masaharu Tokizane, Imao Tamura1971 Volume 35 Issue 4 Pages 401-405
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt is interesting that Fe-Mn-Co ternary martensitic alloy shows a remarkable age-hardening behavior, even though each binary alloy, which composes Fe-Mn-Co ternary alloy, shows no precipitation-hardening response. But this interesting age-hardening behavior has not been clarified yet.
In the present study the age-hardening behavior of Fe-15%Mn-25%Co martensitic alloy was investigated by hardness and electrical resistivity measurements, X-ray diffraction and transmission electron microscopy. The electrical resistivity reached a maximum in the early stage of ageing and then decreased when the formation of γ started. And this γ phase was formed not at the grain or lath boundaries but in the martensite grains and showed a so-called Widmanstätten structure. Furthermore, the aged alloy showed the typical reversion phenomena.
These experimental results suggest that solute rich zones formed in α′ in the early stage of ageing play an important role in the age-hardening of Fe-Mn-Co martensitic alloy. From this viewpoint, a schematic phase diagram was proposed to illustrate the precipitation sequence of this alloy.View full abstractDownload PDF (1729K) -
Ryo Horiuchi, Masahisa Otsuka1971 Volume 35 Issue 4 Pages 406-415
Published: 1971
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to develop and elaborate the Weertman’s theory of creep of solid solution alloys, the high temperature creep test was carried out with Al-Mg alloys. The results are summarized as follows: (1) In alloys containing more than 3 at%Mg, the dependence of the steady-state creep rate on stress and temperature is described by the equation, \dotεs=Aσnexp(−Qc⁄RT), where A is a numerical constant depending on the solute concentration, n≅3 and Qc=33.5±1.5 kcal/mol. (2) Transmission electron microscopy showed that the dislocations were distributed uniformly without forming cell structures. An alternating array of oppositely signed edge dislocations is considered as the most possible distribution. In such a case, the maximum internal stress is estimated to be less than several percent of the applied stress and so is negligible compared with the latter. (3) The measured dislocation density was proportional approximately to the square of the stress and was independent of solute concentration. (4) The experimental relation between the dislocation density and the applied stress is explained theoretically by a model based on the balance between multiplication and annihilation of dislocations. The climb velocity which is estimated from comparison between the calculated and measured creep curves, is in good agreement with the theoretical value. (5) The high temperature creep of alloys is controlled by the viscous motion of dislocations and is proportional to the cube of the stress, provided that the following conditions are satisfied; a large atomic size factor, a rather high solute concentration, a high stacking fault energy and a uniform distribution of dislocations. It is therefore concluded that the high temperature creep of solid solution alloys is not always controlled by the viscous motion of dislocations.View full abstractDownload PDF (2721K)
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