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Volume 44, Issue 10
Displaying 1-17 of 17 articles from this issue
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Tadayoshi Takahashi, Masayuki Kudoh, Kiyoshi Ichikawa1980 Volume 44 Issue 10 Pages 1089-1097
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe solid-liquid coexisting zone was classified into the q and the p zone by the fluidity of the liquid between solids. In the q zone having the range of mass fractions of solid of 0 to 0.67, the liquid between the solids can flow, and in the p zone, which has the range of 0.67 to 1.0, the liquid is entrapped by the solids and cannot flow through the solids. The solidification ranges of the q and the p zones were evaluated by the diffusion-controlled equation introducing the term of the mean solute concentration in solid and are shown in the equilibrium phase diagram of an Al-base binary alloy. The flow length in the fluidity test of binary alloys was corresponding to the reciprocal of the solidification range of the q zone. The strength during solidification originated at a mass fraction of solid of 0.67 on the boundary between the q and the p zones, increased with increasing fraction of solid and rapidly increased at the end of solidification. The crack length in the ring test of binary alloys increased with the width of the primary crystallization in the p zone and the fraction of volume contraction in its zone.View full abstractDownload PDF (766K) -
Tadayoshi Takahashi, Masayuki Kudoh, Keiichi Yodoshi1980 Volume 44 Issue 10 Pages 1097-1104
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSUsing the authors’ method that an artificial hole was made in the solid-liquid coexisting zone, the interdendritic liquid was allowed to flow into the cylindrical hole or the wedgewise concavity for different fractions of solid. The healing phenomena in relation to hot tearing were pursued by the formation mechanism of dendrites within the liquid flowing into the hole.
The results on an Al-3 mass%Si alloy are summarized as follows.
(1) When the diameter of the cylindrical hole was above 4 mm, the occurrence of crystals was recognized in the hole and the hole was healed. In case of the hole of 2 mm diameter, a narrow shrinkage pipe was observed in the central part of the hole.
(2) The formation of the dendrites within the hole becomes possible with increasing diffusion distance of solute in the liquid in front of the dendrites developing from the wall of the hole towards the center of it, because the degree of constitutional undercooling in the central part of the hole increases with increasing the diffusion distance. In the hole of 2 mm diameter without crystallization, the liquid in front of growing dendrites is promoted to be enriched in solute and the solute-rich liquid is utilized as the source of feeding against the solidification contraction of the specimen, so that a shrinkage pipe is formed.
(3) The experimental results of the healing phenomena in case with holes of several diameters could be reappeared with the wedgewise concavity which was made by the procedure similar to the formation of the cylindrical hole in the solid-liquid coexisting zone.View full abstractDownload PDF (1597K) -
Shigeru Asano, Kazuyuki Oguri1980 Volume 44 Issue 10 Pages 1104-1111
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe influence of hydrogen charging on the mechanical properties of several Fe-Cr alloys was examined in detail, in order to investigate some fundamental aspects of hydrogen embrittlement of iron and steel. The change in flow stress caused by electrolytic hydrogen charging was analysed with special attention to the role of an alloying element of chromium and compared with available data on hydrogen diffusion and internal friction. The results obtained are summarized as follows: (1) The fracture elongation of Fe-Cr alloys, containing up to 20 mass% chromium, was always decreased by the introduction of dissolved hydrogen. Such a hydrogen embrittlement became more pronounced with the increase in chromium content. (2) The flow stress of Fe-Cr alloys was always increased by the introduction of dissolved hydrogen. Such a lattice hardening was observed in all the alloys used but no softening was detected. (3) The lattice hardening due to dissolved hydrogen in these alloys became more remarkable with the increase in chromium content, but it was apparently independent of the other minor impurities in the alloys. There is therefore a close phenomenological relationship between hydrogen embrittlement and lattice hardening. (4) The lattice hardening can be explained in terms of the dislocation model adopted so far for the explanation of hydrogen diffusion and internal friction. The increase in flow stress can be expressed as Δσ≈6recEB⁄b, where c is the lattice concentration of dissolved hydrogen, EB the binding energy of hydrogen with dislocations, and re and b the effective radius and the Burgers vector of dislocations, respectively.View full abstractDownload PDF (670K) -
Mitsugu Okamoto, Zenji Hagiwara1980 Volume 44 Issue 10 Pages 1111-1121
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe overall process of hydrogen absorption was divided into such three processes that chemical reaction on the surface between metal and hydrogen, transformation from solution to metal hydride, and diffusion of hydrogen atom (ion) in metal. The authors discussed the rate of reaction by noticing the shape of its curves which represents the reaction in progress.
The results obtained were summarized as follows:
(1) From the hydrogen sorption curves, it was obvious that the rate limiting process changed from surface reaction control to diffusion. The reaction ratio corresponding to the transition from surface reaction to diffusion was 30∼40% and 40∼50% in absorption and desorption, respectively. The rate limiting step in magnesium was shifted to diffusion control after a short stay of about 17% in surface reaction control, because the activation treatment of magnesium was difficult.
(2) The unreacted core model for the reaction rate between spherical particles and gases could be fairly well applied to estimate the controling step of hydriding and dehydriding reactions; ie. at the initial stage surface reaction controls the rate and at the final stage diffusion controls it.
(3) When the hydrogen pressure was higher than 1.7×104 Pa under the present experimental condition, the surface reaction in hydrogen absorbing process followed the first order rate law, but when it was lower than 1.7×104 Pa, the surface reaction might be suggested to be the second order.
(4) The hydrogen absorbing process in metals is considered a series-type reaction by which each process takes place one after another continuously. The overall reaction is controlled by the latest step. It is possible that various defects in metals may give rise to bending in the Arrhenius plot due to the trapping effect of hydrogen.View full abstractDownload PDF (795K) -
Harusige Tsubakino, Ryoichi Nozato, Hiroyasu Mitani1980 Volume 44 Issue 10 Pages 1122-1126
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe influence of Co content on the volume fraction of discontinuous precipitation cells has been investigated in Cu-2 wt%Be-Co alloys containing Co from 0.05 to 1.0 wt% by means of metallographic observations. The variation in the volume fraction of discontinuous precipitation cells, cell radius and interlamellar spacing with Co content in the specimens of a given ageing condition, and also the variation in mean grain diameter with Co content have been determined by quantitative metallographic measurements. The results obtained are as follows:
(1) With increasing Co content, the volume fraction of discontinuous precipitation cells first decreases but passes through a minimum at Co content of about 0.2 wt% and then increases.
(2) With increasing Co content, cell radius and interlamellar spacing first decreases and increases, respectively, but they remain almost constant at higher Co content, while mean grain diameter decreases continuously.
(3) At constant Co content, cell radius does not depend on mean grain diameter but the volume fraction of discontinuous precipitation cells increases with decreasing mean grain diameter.
(4) Then it is considered that the change in the volume fraction of the discontinuous precipitation cells at lower and higher Co content will be attributed to decrease in cell radius and mean grain diameter, respectively.
(5) The influence of Co content on cell radius and interlamellar spacing will be correlated to the equilibrium phase diagram of Cu-Be-Co ternary alloy in view of the driving force for cell growth.View full abstractDownload PDF (532K) -
Harusige Tsubakino, Ryoichi Nozato, Kazuyuki Ishiguro1980 Volume 44 Issue 10 Pages 1127-1133
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe behaviour and kinetics of cell growth in a secondary coarse lamellar pearlite reaction in Cu-22.6 at%Be alloy have been studied principally by metallographic observations. The variations in cell radius, interlamellar spacing and volume fraction of γ phase in pearlite cells with ageing time have been determined by quantitative metallographic measurements of the specimens aged at temperatures from 673 to 823 K.
The results obtained are as follows:
(1) After initial, fine lamellar pearlite reaction has almost completed, coarse lamellar pearlite reaction occurs wherein the fine pearlite is replaced by the coarse pearlite.
(2) Cell growth rate of coarse pearlite decreases, and the interlamellar spacing increases with ageing time.
(3) Interlamellar spacing of coarse pearlite is 4∼5 times larger than that of fine pearlite in every ageing time.
(4) Be concentration of α phase in fine pearlite is supersaturated at the initial ageing stage, then decreases with ageing time and attains an equilibrium value prior to the occurrence of a coarse pearlite reaction. Then it is considered that there are no chemical free energy changes during the cell growth of coarse pearlite.
(5) Grain boundary diffusivities, evaluated from the discontinuous coarsening model proposed by Livingston and Cahn are reasonable. Therefore, it can be concluded that the cell growth of coarse pearlite occurs by the discontinuous coarsening mechanism.View full abstractDownload PDF (920K) -
Hisashi Kuwano, Yasuhiro Morooka1980 Volume 44 Issue 10 Pages 1134-1138
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe isomer shift of 57Fe in Fe1−xCrx alloy is measured at room temperature in a concentration range from x=0.028 to x=0.967, and the data are discussed in terms of changes in the 4s-like and 3d-like electron configuration of Fe atoms and volume changes, which are introduced by the solution of Cr atoms to iron matrix, as follows: (1) In the concentration range x=0.13 to x=0.967, the isomer shift, IS, decreases linearly with increasing chromium content, x, giving an empirical equation: IS=−0.145x. This is explained in terms of the increase in the number of 4s-like electrons of Fe atoms with the increase of x. (2) In the range x=0.028 to x=0.13, the isomer shift deviates in the positive direction from the above equation, showing a maximum around x=0.03∼0.05. Most likely the deviation is primarily related to the change in the number of 3d-like electrons of Fe atoms, as proposed by Sauer and Reynik, and secondary to the volume change.View full abstractDownload PDF (318K) -
Motohiro Kanno, Hisashi Suzuki, Osamu Kanoh1980 Volume 44 Issue 10 Pages 1139-1145
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe θ′ precipitation was studied in an Al-4%Cu-0.060%In alloy aged at 473 K by transmission electron microscopy, EDXS analysis, etc., to clarify the phenomenon of aging acceleration widely known in this alloy. The aging structures of Al-4%Cu-0.065%Sn and Al-4%Cu-0.096%Cd alloys as well as Al-4%Cu alloy were also studied.
It was found that indium rich precipitates formed finely at an early stage of aging, resulting in the heterogeneous nucleation of θ′ on those precipitates. The results were common in three sorts of ternary alloys. However, some differences in hardening rate and peak hardness were observed among the alloys, and these differences were attributed to the difference in size and distribution-density of In, Sn or Cd rich precipitates acting as a nucleation site for θ′.View full abstractDownload PDF (1568K) -
Minoru Takahashi, Yuji Ueda, Katuhiko Sudo, Yoshiharu Naruse1980 Volume 44 Issue 10 Pages 1145-1150
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA thermal expansion measurement apparatus was designed in order to measure the thermal expansion characteristics of ribbon specimens of 10∼50 μm thickness and of thin wires of less than 0.1 mm diameter. The differential transformer and balancing method was used for the apparatus.
Thermal expansion curves were measured in the temperature range 77∼800 K by changing the weight applied to the specimens and by changing the heating rate in order to find the most suitable measuring condition.
The shape of the thermal expansion curves varied remarkably with the applied weight. The most suitable weight to measure the thermal expansion was 1.5∼2.5 MPa. The magnetostriction for amorphous Fe83B17 alloys was measured by appling a magnetic field of 3 A/m.View full abstractDownload PDF (423K) -
Naotake Niwa1980 Volume 44 Issue 10 Pages 1151-1155
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe present study deals with the effect of annealing on strain and stress paths to fracture in the ductile fracture process of tough-pitch copper round bar specimens pulled in tension. A neck shape change with the development of necking was examined through measurements of the radius and curvature ratio of the neck contour. In addition true flow stress in the neck was presumed by using the correction factor proposed by Davidenkov et al.
Differences in fracture strain resulting from annealing were almost invariably due to those in strain up to maximum load. The post-instability strain to fracture was almost the same for differently annealed specimens.
All specimens were fractured through similar changes of neck shape with the development of necking. Stress path up to maximum load was different for each annealing condition. However, that from the onset of necking to fracture was almost the same independently of annealing conditions. The maximum in true flow stress was found prior to fracture onset. This corresponds to the condition for the second mode of flow localization, proposed by Chakrabarti et al. This mode of flow localization is thought to provide a good explanation of phenomena observed in the fracture process of tough-pitch copper round bar specimens.
As annealing in the ductile fracture of these tough-pitch copper specimens, ductile fracture factors might have different effects on the uniform deformation process up to the onset of necking and on the process of deformation under hydrostatic stress caused by necking. Therefore, it appears necessary to examine the effects of ductile fracture factors separately for these two processes.View full abstractDownload PDF (406K) -
Keijiro Nakasa, Hideo Takei, Motoharu Yoshida, Toshiyuki Saito1980 Volume 44 Issue 10 Pages 1156-1163
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe macroscopic crack branching behavior in delayed failure was investigated on the high strength Ni-Cr-Mo steel with various pre-austenite grain sizes. There appear two regions in the relation between crack propagation velocity da⁄dt and stress intensity factor K, i.e, the region I, where da⁄dt increases with increase in K, and the region II, where da⁄dt is constant independent of K and macroscopic crack branching is observed. The crack propagation velocity in the two regions increases with increase in grain size and testing temperature, and stress intensity factor dependency of da⁄dt in region I increases with increase in grain size. The stress intensity factor at crack branching, KIB, increases with increase in grain size and temperature. However, the crack branching does not occur in a larger grain size and at a higher temperature. The grain size and temperature dependency of KIB can be well explained by using the assumption that the crack branching occurs when the trapping of hydrogen atoms by dislocations and microvoids causes the broadening of the diffusion path of hydrogen atoms at a crack tip.View full abstractDownload PDF (736K) -
Tadashi Maki, Shinobu Nakagawa, Imao Tamura1980 Volume 44 Issue 10 Pages 1164-1170
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSRecrystallization behavior of austenite cold rolled or formed by the α′→γ reverse martensitic transformation was investigated using Fe-33Ni, Fe-35Ni and Fe-25Ni-0.4C austenitic alloys. The main results obtained are as follows.
(1) In the case of Fe-35Ni alloy in which slip deformation occurs by cold rolling of 20∼80%, recrystallized grains are preferentially formed along the austenite grain boundaries. The number of recrystallized grains formed along austenite boundaries increases with increase in the amount of prior deformation. When specimens were slightly deformed by 20%, the recrystallization also occurs by the bulging mechanism of existing austenite grain boundaries.
(2) The Fe-25Ni-0.4C alloy is deformed not only by slip but also by twinning when cold rolled by 50%. In such a case, many recrystallized grains are preferentially formed at the intersections of deformation twins within austenite grains. Because of such a preferential nucleation at deformation twins, austenite grain size after recrystallization in Fe-25Ni-0.4C becomes much smaller than that in Fe-35Ni.
(3) The Fe-33Ni martensite which are formed by subzero cooling to 77 K transforms to austenite by shear mechanism during heating. Reversed austenite boundaries correspond to prior austenite boundaries before heating. Recrystallized grains are preferentially formed along grain boundaries of reversed austenite. The number of recrystallized grains in the reversed austenite are very few. Therefore, the austenite grain refinement by recrystallization is not observed in the case of reversed austenite in Fe-33Ni alloy.
(4) When the Fe-25Ni-0.4C martensites which are formed by subzero cooling to 77 K are heated up above the Af temperature, the reversed transformation occurs mainly by the shear mechanism, but partly by the diffusional process because of the rapid carbide formation in martensites on heating. In this case, fine austenite grains which are formed by the diffusional transformation are observed within reversed austenite grains, in addition to the few recrystallized grains at the reversed austenite grain boundaries.View full abstractDownload PDF (1630K) -
Hiromitsu Ino, Tsunenori Ito, Saburo Nasu, Uli Gonser1980 Volume 44 Issue 10 Pages 1171-1179
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMössbauer spectra of Fe-1.5∼7.2 at%C alloys without and with 5T longitudinal external magnetic field were measured to clarify the structure of iron carbon martensite. The spectra of freshly quenched martensite are decomposed into three magnetic hyperfine patterns having different fields. The 1st component with a hyperfine field of (H\simeq27T) is identified as the absorption caused by 1st neighboring iron atoms of octahedral carbon atoms. The 2nd component (H\simeq31.5T), the intensity of which rapidly decreases during aging, is due to 1st neighboring iron atoms of tetrahedral carbon or possibly 2nd nearest neighbors of octahedral carbon atoms. The 3rd main component (H\simeq34T) is due to iron atoms not much perturbed by farther carbon neighbors.
The appearance of three additional components (H\simeq37, 26.5 and 18T) in the aged martensite indicates the formation of the ordered non-stoichiometric Fe4Cx (x<<1) phase. The Mössbauer spectra of the ε (or η) carbide formed after aging at 313 K are decomposed into three hyperfine components corresponding to different iron environments in the carbide, suggesting the existence of vacant sites of carbon in the Fe2C structure.View full abstractDownload PDF (651K) -
Yuji Tsukamoto, Hiroaki Sasaguchi, Fusao Hayama1980 Volume 44 Issue 10 Pages 1180-1187
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn the previous paper the authors proposed that friction and wear behaviours between mild steel and various brasses could be explained by the prow formation mechanism. The present test program was carried out to clarify some effects of the mating materials on the adhesive wear characteristics of various brasses. Five different metals (i.e. mild steel, medium carbon steel, hardened carbon steel, α brass and α+β brass) were selected as pin specimens, and unlubricated low speed wear experiments were conducted on nine sliding pairs.
The wear behaviour of α brass ring specimens depended on the mating materials. Since substantial prow growth took place on the simillar pair of α brass, the ring specimen showed a higher wear rate than that of the other couples as expected from the empirical laws. The mild steel-α brass combination exhibited the transition from the running-in period to the steady state having a lower wear rate. This transition is accompanied by the prow formation process which involved the break-away near the interface between the prow and a pin specimen. It is interesting to note that the deformation twin region is formed below the wear track of α brass slid against mild steel.
The wear characteristics and prow formation processes of α+β brass were governed mainly by the plastic shearing deformation properties following continuous prow growth, especially sliding systems of α+β brass and various carbon steels showed essentially identical prow formation processes. On the simillar pair of α+β brass a prow broke away along the crack propagated into the pin specimen, and the surface was worn out to flat.View full abstractDownload PDF (1103K) -
Fumio Kurosawa, Isamu Taguchi, Ryutaro Matsumoto1980 Volume 44 Issue 10 Pages 1187-1193
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAn analytical method for determination of Gamma prime in Ni-base alloy (1.1Al-2.25Ti-14.7Cr-8.9Fe) has been studied using the potentiostatic method with the non-aqueous electrolyte.
The results obtained are summarized as follows.
(1) In order to extract quantitatively gamma prime from specimens, 3% nitric acid-2% perchloric acid-methyl alcohol electrolyte and +1300 mV vs SCE are recommended as an electrolyte and electrolytic potential, respectively.
(2) In order to determine the elements in extracted gamma prime, a rapid method is established. Nickel is determined by a volumetric method or ICP method. Aluminium, titanium, chromium and iron are determined by a ICP method.
(3) The analytical results of gamma prime was found to be about 5% in the as cast specimen.
The percentage of gamma prime increased according to the aging time at 973 K up to 15.5% after 3.6 Ms aging.
(4) The percentage of nickel in the extracted residues increased according to the aging time.
On the contrary, those of titanium, aluminium and chromium decreased gradually but that of iron remained constant. According to the analytical results, the chemical composition form of gamma prime in the specimen was represented as Ni2.88Al0.37Ti0.51Cr0.12Fe0.12 in case of the 360 ks aging specimen, if the form was assumed as Ni3(Al, Ti).
(5) Gamma prime grew up according to the aging time up to about 40 nm after 3.6 Ms aging.View full abstractDownload PDF (1325K) -
Mitsuo Asawa1980 Volume 44 Issue 10 Pages 1194-1199
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSStress corrosion behavior of Type 304 stainless steel wire in 2 kmol/m3 H2SO4-NaF at 368 K was examined as functions of both the amount of α′ martensite induced by prestraining at various temperatures under a stress of 324 MPa and the NaF concentration of the test solutions.
Crack occurred when the steel containing a small amount of α′ martensite induced at temperatures higher than 273 K was tested in a solution containing 1.9 kmol/m3 NaF, in which corrosion of solution annealed Type 304 steel was suppressed at early stages of testing. General corrosion, on the other hand, was observed when the steel contained a large amount of α′ induced at temperatures below 273 K and/or when NaF concentrations of the test solution were below 1.5 kmol/m3, in which the decrease in corrosion rate of solution annealed Type 304 steel with time was small.
The above results have been interpreted in the same manner as in the previous work on Type 304 steel in H2SO4 aqueous solutions containing NaBr or NaI, that is, in terms of preferential dissolution of α′ martensite and chemical stability of the protective layer of the corrosion product on the steel.View full abstractDownload PDF (1110K) -
Yukio Ohba, Tadayuki Fujii1980 Volume 44 Issue 10 Pages 1200-1201
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (171K)
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