All issues
Volume 48, Issue 2
Displaying 1-17 of 17 articles from this issue
- |<
- <
- 1
- >
- >|
-
Kenichi Murakami, Yukihisa Murakami, Kenji Mishima, Yasushi Ikai1984 Volume 48 Issue 2 Pages 115-121
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSResistivity to degradation due to repeated martensitic transformation of Cu-base shape memory alloys is evaluated through optical reflectivity measurements. The repeated martensitic transformation generates dislocations and then internal stress. Irreversible martensites become to appear, and they accommodate them selves to the internal stress. They are increased in amount with increasing thermal cycles. Internal stress shifts Ms to a higher temperature side and Mf to a little lower temperature side.
Cu-Zn-Al alloys with finer grain size are more resistive to thermal cycling. One of them with the finest grain size has nearly the same thermal resistivity as a Ti-Ni allay. The grain size refinement is done by adding small quantities of Ni, Pb, Ce, Cr, B, and Zr. The Cu-Zn-Al allay with the smallest grain size (≤20 μm) shows less sharp hysteresis curves.View full abstractDownload PDF (1258K) -
Yukiteru Asayama1984 Volume 48 Issue 2 Pages 122-128
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPrecipitation behaviors of 18%Ni maraging steels containing Ti were studied by measuring the electrical resistivity at liquid nitrogen temperature.
On isochronal aging, Mo-rich zones which are significant precipitates in lower temperature aging, are formed following the precipitation of Ni3Ti(DO3) ordered phase at lower temperature region, and a metastable Ni3Mo phase is produced after the precipitation of Ni3Ti(DO24)η phase at higher temperature region.
The presence of Co contributes not only to acceleration of the precipitation of Mo-rich zone, but also to promotion of the precipitation of Ni3Ti(DO3) ordered phase.
On isothermal aging in the 18%Ni maraging steels with lower Ti content, decrease of the electrical resistivity is predominantly governed by the precipitation of Ni3Mo at temperatures over 753 K, but the 18%Ni maraging steels with higher Ti content always show the decrease of the electrical resistivity governed by the precipitation of Mo-rich zone at an early stage of the aging, even at 753 K and more, because the precipitation of Ni3Mo is retarded by presence of Ni3Ti(DO24)η phase.
The activation energy for the precipitation reaction of Mo-rich zone increases with Ti content in the 18%Ni maraging steels. The activation energy in the steels without Ti is estimated at 150 kJ/mol by extrapolation from the relationship between the activation energy and Ti content, and the value is consistent with the data reported previously.
It is presumed that the reason why the activation energy in the precipitation reaction of Mo-rich zone increases with Ti content is that precipitation sites of Mo-rich zone are occupied by the Ni3Ti(DO3) ordered phase produced prior to the precipitation of Mo-rich zone, and the Ni3Ti(DO3) precipitates form a potential barrier against the precipitation of Mo-rich zone.View full abstractDownload PDF (959K) -
Keijiro Nakasa, Hisashi Itoh, Hideo Takei1984 Volume 48 Issue 2 Pages 129-135
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to clarify the crack propagation behavior in delayed failure under repeating load, the stress intensity factor K was trapezoidally applied to the specimen, and the relation was investigated between K increasing or decreasing time, t1 or t3, and the incubation time, tu or td, which appeared while K was held at a maximum or minimum value.
The incubation time td is always longer than tu, and td rapidly and tu gradually decreases with increase of t1 and t3. Both tu and td decrease with increase of testing temperature T. The Arrhenius relation holds between 1⁄T and 1⁄tu or 1⁄td, giving the activation energy of 20 or 40 kJ/mol, which is comparable with that for the diffusion of hydrogen atoms in steel.
The appearance of incubation time after the abrupt change in K can be explained by assuming that hydrogen diffusion occurs later than moving of triaxially tensile stressed position at a crack tip.View full abstractDownload PDF (1016K) -
Keijiro Nakasa, Hideo Takei, Hisashi Itoh, Masayoshi Kobayashi1984 Volume 48 Issue 2 Pages 136-143
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSHydrogen cracking tests under repeating stress were carried out on specimens hydrogen precharged, and the effect of stress ratio was investigated on the relations between frequency f and the decreasing rate of crack propagation velocity, 1−β={(da⁄dt)S−(da⁄dt)R}⁄(da⁄dt)S, where (da⁄dt)S and (da⁄dt)R were the crack propagation velocity under static and repeating stress, respectively. The results were analyzed by using an asymmetrical internal friction model proposed.
There appear two peaks on 1−β vs. f curve, as do in the delayed failure test under repeating stress in water, i.e. this phenomenon is controlled by the migration and concentration process of hydrogen atoms to triaxially tensile stressed position near crack tip. With increase in stress ratio R=Kmin⁄Kmax, the two peaks approach each other, the height of peaks decreases, and the frequencies at which two peaks appear shift to the higher frequency ranges.
The existence of two peaks on 1−β vs. f curve and the characteristic change in 1−β vs. f curve with change in the stress ratio, can be explained by assuming the interaction between hydrogen atoms and the cyclic moving of triaxially stressed position. Furthermore, 1−β vs. f relations calculated using the asymmetrical internal friction model reveal a good agreement with the experimental tendencies.View full abstractDownload PDF (1206K) -
Mitsunori Tsutsui, Takashi Yamada, Rikuro Otsuka1984 Volume 48 Issue 2 Pages 144-150
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe purpose of the present study is to investigate the effects of heat treatment on the hydrogen embrittlement of chromium molybdenum steel containing 0.35%C, 1.05%Cr and 0.15%Mo. The specimens were deformed at a constant slow stress rate with cathodic hydrogen charging simultaneously.
The susceptibility to the hydrogen embrittlement of the specimens was evaluated from the loss in strength caused by hydrogen absorption. On the other hand, the hydrogen content was estimated as a function of tempering temperature by means of the electrochemical permeation technique.
The results are as follows:
(1) The susceptibility to hydrogen embrittlement of chromium molybdenum steel varied with tempering temperature. The tensile strength of the specimens tempered below 823 K decreased markedly by hydrogen charging. The maximum loss in strength was obtained at tempering temperature of 673 K.
(2) The diffusion coefficient of hydrogen increased with increasing tempering temperature, and the content of hydrogen decreased conversely.
(3) The tensile strength of hydrogen charged specimens recovered to the same level as that of the hydrogen free specimen by leaving them in air for 345.6 ks after hydrogen charging.
It is suggested that the hydrogen embrittlement is not caused by hydrogen, which is fastened tightly at trap sites, but by diffusible hydrogen.View full abstractDownload PDF (1307K) -
Naotsugu Inakazu, Hisashi Yamamoto1984 Volume 48 Issue 2 Pages 151-157
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe measurement of mechanical properties and the torsion fatigue test were carried out to find the correlation between the static strength and the torsion fatigue strength with various drawing ratios for the metastable austenitic stainless steel.
The tensile strength and elongation of the SUS 304 steel indicated higher values than those of the SUS 305J1 and XM7 steels, because the influence of the TRIP effect was the greatest on SUS 304 steel, but as for the workability the SUS 305J1 and XM7 steels were better than 304 steel.
Regarding the torsion fatigue strength, the durability of SUS 304 steel was the lowest, because the formation of induced martensite in SUS 304 steel accelerated the sensitivity against a crack-propagation during the fatigue test, while the durability of SUS 305J1 and XM7 steels was higher, because the development of the induced martensite did not hardly occur.
It was found that the development of the induced martensite improved the static strength with the TRIP phenomenon, but damaged the torsion fatigue strength.View full abstractDownload PDF (1617K) -
Yasuya Ohmori, Yasuhiro Maehara1984 Volume 48 Issue 2 Pages 158-163
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of NbC precipitation on hot deformation of austenitic stainless steels has been studied with particular emphasis on ductility. The mechanism for reducing ductility in the temperature range where NbC precipitation occurs can also explain the surface cracking mechanism of continuously cast low alloy steel slabs. The ductility trough in slow strain rate tensile tests at around 1073 K in Nb-bearing steels is accompanied by the intergranular microvoids coalescence mode of fracture. This ductility loss is induced by rather coarse NbC particles precipitated on the grain boundaries, the precipitation free zones along the grain boundaries and the dynamic precipitation of fine NbC particles within the grains. That is, when an external stress is applied, the strain will be concentrated within the soft layers of precipitation free zones by the matrix strengthening due to fine dispersion of NbC. This will lead to the decohesion of the NbC/matrix interfaces on grain boundaries, resulting in the intergranular microvoid coalescence.View full abstractDownload PDF (3769K) -
Toshiaki Yoneoka, Michio Yamawaki, Masayoshi Kanno1984 Volume 48 Issue 2 Pages 164-172
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSOxidation behaviour of vanadium-aluminum alloys containing 5 and 10 at% aluminum has been investigated at temperatures ranging from 800 to 993 K in oxygen pressures of 1.33 and 133 Pa by means of a thermo-electrobalance, an X-ray diffractometer, an electron probe microanalyzer, a micro-hardness tester as well as metallographic techniques. Whereas mass gain due to oxidation initially followed the parabolic rate law, it then turned into linear kinetics, resulting in paralinear-like behaviour in most cases. The improvement of oxidation resistance of vanadium due to alloying aluminum became higher with decreasing temperature, while the effects of alloy composition and oxygen pressure were nearly negligible. The alloys of both compositions exhibited similar oxidation kinetics and scale structures to each other. The typical oxide scale was composed of three layers: an outer layer of nearly pure VO2, an intermediate VO2+Al2O3 layer and an inner V2O3 layer. The amount of oxygen dissolved into substrates of these alloys was reduced at temperatures up to 897 K, while it increased at 993 K compared with that for pure vanadium. This decrease in oxygen dissolution can be ascribed to the decrease in oxygen diffusivity due to addition of aluminum, whilst the increase in oxygen dissolution is attributable to internal oxidation of aluminum. The activity of aluminum in vanadium-aluminum alloys was found to be remarkably low, which affected the oxidation behaviour of these alloys.View full abstractDownload PDF (2999K) -
Yasuo Uchiyama, Hideto Koga, Takao Ohkubo, Akio Sasada1984 Volume 48 Issue 2 Pages 173-180
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSFe-C binary alloys, Fe-Si binary alloys, Fe-C-Si ternary alloys and several commercial alloys were immersed in a pure zinc bath at 733 K for 600 s, and the structures and the thicknesses of alloy layers formed and quantities of iron having reacted with zinc were measured, in order to clarify the effect of carbon and silicon in steel on the Fe-Zn reaction.
The reactivity of Fe-C binary alloys does not depend on the carbon concentration. The reactivity of Fe-Si binary alloys increases up to about 0.1 mass%Si, decreases in a region of 0.25 mass%Si and then increases with increasing silicon concentration. It is found that the carbon and silicon in steel have the interaction on the Fe-Zn reaction, and in the high silicon concentration the carbon promotes the growth of a zeta layer and suppresses the growth of a (delta 1+eta) mixture layer which is promoted by the silicon.View full abstractDownload PDF (2215K) -
Tsutomu Harada, Sh\={o}ichiro Fujimoto, Akira Iwata, Kusuhiro Mukai1984 Volume 48 Issue 2 Pages 181-190
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSLocal corrosion of solid oxides at the surface of liquid slags has been investigated in Ar atmosphere for the following systems: Mgo, Al2O3-(CaO-Al2O3-SiO2) slag, MgO-(CaO-Al2O3-SiO2-B2O3, P2O5) slag and SiO2-(CaO-FeO-SiO2) slag. Phenomena of the local corrosion observed for these systems and also SiO2-(PbO-SiO2) slag systems reported by the authors(1) are explained fundamentally from the standpoints of interfacial turbulence of creeping up slag film along the surface of the specimen above the slag surface and mass transfer of the dissolved component of the specimen in the bulk slag by density current and diffusion etc. Appearance of the local corrosion, that is, its shape and time variation of Δds-g, the linear loss of the specimen, have been classified, based on the characteristic physicochemical properties of each system, such as the surface tension of the slag, the density of the slag, the wettability of the system, the solubility of the solid oxide in the slag and the rate of corrosion, dΔds-g⁄dt.View full abstractDownload PDF (3814K) -
Hiroyuki Kaneko, Hitoshi Taimatsu1984 Volume 48 Issue 2 Pages 191-197
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA micro-computer controlled measuring system for the current distribution on a flat specimen immersed in an electrolyte was presented: The horizontal and normal potential changes on a plane in the solution adjacent and parallel to the specimen surface measured by scanning a set of two Luggin probes are set on-line to the input of a micro-computer, to analyze the current distribution and to display current maps on a CRT display.
The system was applied to the study of typical galvanic and pitting corrosions. Current maps obtained on the specimens consisting of copper-zinc couples demonstrated that zinc dissolved drastically along the copper-zinc boundary. A sequence of current maps with time obtained on a commercial aluminum demonstrated distinctly the generation and the growth process of pits.
Therefore, the measuring system developed in this study can be widely applicable to the in situ evaluation of local corrosion current as well as to the detection of corroding sites on a specimen.View full abstractDownload PDF (2309K) -
Akira Okada, Yasushi Yoshinaga1984 Volume 48 Issue 2 Pages 197-202
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe dry wear characteristics of chopped carbon fiber-(Al-Cu) composites containing 8.7 to 32 vol%CF produced by the powder metallurgy process were investigated by using a pin-rotating cylinder type wear test apparatus.
The wear volume of the composites was reduced to about 1/3 to 1/6 of that of sintered Al-Cu material under loads, 0.98 N and 1.96 N, and under a higher load, 3.43 N, to 2/3 to 1/3. The reduction of the wear by introducing CF is considered to be smaller for higher contact pressures, and the wear-distance-ratio is larger for the initial stage of wear process, when the apparent contact pressure is high. These results may be due to lack of bond formation between CF and the metal matrix. The wear volume could be considered to be inversely proportional to the CF content, and decrease in the wear volume with increasing CF amount was much larger than the reduction of friction coefficient.
It may be presumed that the higher loading capacity of CF may be rather responsible than its lower frictional characteristics for the good wear resistance of the CF-(Al-Cu) composites.View full abstractDownload PDF (1654K) -
Sadami Tomita, Hideo Suzuki1984 Volume 48 Issue 2 Pages 202-208
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn manufacture of amorphous ribbon by the single roll method, there are several unknown factors which affect the ribbon shape i.g. thickness and smoothness. It has experimentally been established that the ribbon shape is influenced by the roll rotating speed, the ejection gas pressure, the nozzle tip profile and the gap distance between the nozzle and the roll, but the mechanism by which these process conditions affect the ribbon shape formation has not been explained yet.
By the observation of a puddle held at the nozzle tip and also by the temperature measurements of the roll and ribbon surface, we can analyze the relationships between the amorphous ribbon shape and process conditions.
Ribbons of Fe70Ni8Si10B12 composition having 10-36 μm thickness were prepared using iron or copper rolls. In experiments in which the rotating speed and ejection pressure were varied, we observed that the puddle stayed in the vicinity of the nozzle tip and the ribbon was extracted from there. Thus, we concluded that the thickness of the amorphous ribbon was determined immediately by the solidified layer and fluid motion layer, while holes and dents on the ribbon surface were caused by gas bubbles caught at the interface between the roll and melt.View full abstractDownload PDF (1444K) -
Hisashi Suzuki, Motohiro Kanno, Takao Maeda1984 Volume 48 Issue 2 Pages 209-213
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe half-softening temperature (TH) and the electrical resistivity of cold-worked pure copper were studied in relation to the additional amount (up to 1000 mol ppm) of transition elements such as Ti, Zr, Hf, V, Cr, Mn and Fe. The specimens were in vacuum melted, cast, homogenized at 1073 K, quenched and then cold-worked. It was found that TH of each specimen decreased with the additional amount as small as 10-30 mol ppm and that the electrical resistivity of each specimen, in a cold-worked or annealed state, was almost the same as that of pure copper in the range of addition up to about several mol ppm. These results would be caused by the interaction between a certain impurity in pure copper and additives. Further addition increased TH and the electrical resistivity of copper. It was shown that the material with extremely high TH and excellent conductivity was obtainable by a trace addition of Zr or Hf of only about 170 mol ppm.View full abstractDownload PDF (1146K) -
Hisashi Suzuki, Koji Hayashi, Hideaki Matsubara, Kunio Shibuki1984 Volume 48 Issue 2 Pages 214-219
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA titanium nitride layer was deposited mainly onto HIP-treated WC-10%Co substrate by ion plating (PVD) process at 773 K. The structure at an interface between substrate and layer, and the transverse-rupture strength (TRS) of the coated alloy were examined as a function of the layer thickness (\lesssim5 μm), the surface state of substrate (ground or polished) etc. The effect of annealing of the coated alloy on the structure and strength was also examined.
It was found that a foreign phase having no definite crystal structure formed generally at the interface. The thickness of this phase (\lesssim0.5 μm) did not vary with the layer thickness, but with the surface state of substrate. The foreign phase changed to η(Co3W3C) by annealing at 1073-1173 K. The foreign phase formation would be due to the diffusion of carbon atoms in the substrate near the interface into the coated layer. The TRS of the coated alloys decreased with increasing thickness of the layer, showing that the adhesion between substrate and layer was sufficient by the formation of non-equilibrium phase as above. The TRS was higher, when the substrate surface was in a ground state. When the coated alloys were annealed, the TRS decreased with increasing annealing temperature. It was shown that the fracture of the coated alloys generally took place at the moment of fracture of the coated layer, in other words, the TRS of the coated alloys was mainly controlled by the strength of layer.View full abstractDownload PDF (1718K) -
Naoji Nakamura1984 Volume 48 Issue 2 Pages 220-226
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMeasurements of the magnetic properties, the thermal expansion, the electrical resistivity and the hardness were carried out for Fe-0-3 mass%Nb-4-0 mass%Ta-20 mass%Co-3 mass%Mo alloys. All the alloys used in this study were water-quenched from 1323 K, cold-drawn to 97.2% reduction in area and subsequently reheated at 673-1273 K for the period less than 18 ks. The magnetic properties of alloys depend remarkably on the contents of niobium and tantalum, and the reheating temperature and time.
When water-quenched, cold-drawn and subsequently reheated at 973 K for 1.8 ks, an Fe-1.5%Nb-1.5%Ta-20%Co-3%Mo alloy exhibits the following values: B8 at 8 kA·m−1=1.96 T, Br=1.86 T, Br⁄B8=0.95, Hc=1.89 kA·m−1, \sqrt(BH)max⁄BrHc=0.95, the mean thermal expansion coefficient αT at 273-313 K=9.0×10−6 K−1, the electrical resistivity ρ=0.262μΩ·m and Vickers hardness Hv=391. Also, using ferro-niobium for metallic niobium as raw material, an Fe-1.5%Nb-0.5%Ta-20%Co-3%Mo alloy reheated at 1023 K for 0.6 ks exhibits the following values: B8=2.00 T, Br=1.86 T, Br⁄B8=0.95, Hc=1.75 kA·m−1, \sqrt(BH)max⁄BrHc=0.95, αT=8.8×10−6 K−1, ρ=0.265 μΩ·m and Hv=444.
Thus the Fe-Nb-Ta-Co-Mo alloys “Recalloy” is practically suitable to the reed blade in remanent reed switch. Further, there is such a big merit that the expensive cobalt content in Recalloy is 1/2-1/4 as compared with that of semihard magnetic materials having most practical use.View full abstractDownload PDF (1670K) -
Hakaru Masumoto, Masakatsu Hinai, Showhachi Sawaya1984 Volume 48 Issue 2 Pages 227-232
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe damping capacity, the magnetic property and the anodic polarization behavior were investigated on ternary Fe-Co-Cr alloys with Co less than 30% and Cr less than 40%. Measurements of the internal friction Q−1, the coercive force Hc and the pitting potential Ep were carried out using an inverted torsion pendulum, an automatic recording fluxmeter and a potentiostat, respectively.
In the furnace-cooled state, a fairly high Q−1 value was obtained in two composition ranges of Fe-3-5%Co-17-22%Cr and Fe-5-25%Co-0-5%Cr. Upon water-quenching, the Q−1 value of alloys containing a large amount of Cr increased remarkably, but that of the alloys containing a small amount of Cr decreased considerably.
The Q−1 of the alloys in the state of α solid solution was very high because of the small Hc. The alloys, in which the α-γ transformation strain remained and the σ, γ or ε phases precipitated in the α phase matrix, were lower in Q−1 because of the large Hc.
In all cases the Fe-Cr binary alloys became higher in Ep with increasing Cr content, and the Co addition resulted in a further increase. The Ep of the water-quenched alloys was generally higher than that of the furnace-cooled alloys.View full abstractDownload PDF (761K)
- |<
- <
- 1
- >
- >|