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Volume 42, Issue 2
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[in Japanese]1995 Volume 42 Issue 2 Pages 134
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (52K) -
Minoru Umemoto1995 Volume 42 Issue 2 Pages 135-140
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe enhancement of thermoelectric properties of p-type β-FeSi2 doped with Mn and Al by mechanical alloying (MA) was described. The pre-mixed powder of nominal composition Fe30Si70 transforms to a homogeneous β-FeSi2 phase in the as milled condition. The appropriate milling time of a powder for sintering was around 720 ks at which the powder consists of very fine Fe and Si crystals in the as milled condition. Specimens prepared by hot pressing from MA powder showed lower thermal conductivity, higher figure of merit and hence higher conversion efficiency than those prepared from ingot metallurgy. This was mostly due to the small grain size obtained by MA. Phase formation sequence in MA powder was discussed in conjunction with thin films. The formation sequence of β-FeSi2 from the mixture of Fe and Si powders via ε-FeSi observed in MA powder and thin films of Fe with a Si substrate can be explained with the proposed two rules when the non-stable phases at room temperature were excluded. The possibility of the influence of MA energy on the phase formation sequence was also pointed out.View full abstractDownload PDF (396K) -
Shinya Shiga, Minoru Umemoto, Isao Okane1995 Volume 42 Issue 2 Pages 141-145
Published: February 15, 1995
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThermoelectric generation has drawn world wide attention to convert thermal energy into electrical energy. There are two factors evaluating thermoelectric properties, one is effective maximum power (Peff) and the other is maximum conversion efficiency (η max). The reduction in thermal conductivity (K) increases the temperature difference across a thermoelectric material (Δ T) located between heat source and sink. The increase in Δ T increases the Seebeck potential and hence Peff. The reduction in K increases the figure of merit (Z) and then increases η max. As a whole the reduction of K increases Peff as well as η max.
The substantial improvement of thermoelectric properties can be expected by using composite which consist of a thermoelectric material and a good conductor. Simple calculation made under the assumption that α = f⋅α (Cu)+(1-f)⋅α(β), 1 / ρ = f / ρ (Cu)+(1-f) / ρ (β), K=f⋅K(Cu)+(1-f)⋅K(β) indicates that Peff and η max of β-FeSi2 and Cu composite with a few vol% of Cu can be 24 and 12 times larger than those of β-FeSi2. Here, f is volume fraction of Cu, α (Cu) and α(β) are seebeck coefficient, ρ (Cu) and ρ (β) are specific resistance, K(Cu) and K(β) are thermal conductivity of Cu and β- FeSi2, respectively.View full abstractDownload PDF (309K) -
Masafumi Miyajima, Gil Geun Lee, Ryuzo Watanabe1995 Volume 42 Issue 2 Pages 146-150
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSA ball milling experiment was carried out with a powder premix of Bi and Sb to investigate the mechanical alloying effect on the thermoelectric properties of Bi-Sb thermoelectric semiconductor.The milling process and phase formation were monitored by X-ray diffraction analysis (XRD), SEM and EDX of the milled powders. The milled powders were sintered by hot-pressing. The microstructure of the sintered compacts was observed by TEM, and the electrical properties of compacts were measured by Van der Pauw method at room temperature and 77K.
The X-ray diffraction analysis showed that the Bi92.5Sb7.5 solid solution was formed after 16 hours milling. The sintered compacts have a ultra-fine microstructure with an average grain size of less then 1μm, and the grain size decreased with increase in milling time. The electrical properties of sintered compacts varied with milling time. The electrical resistivity slightly decreased with increase in milling time, which considered to be due to decreasing of carrier density and increasing of carrier mobility with milling time.View full abstractDownload PDF (1428K) -
Hiroshi Nagai, Shogo Nakayama, Shigeru Katsuyama, Kazuhiko Majima1995 Volume 42 Issue 2 Pages 151-155
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe thermoelectric properties of n-type β-FeSi2 doped with Cu were investigated. Mixture of Fe, Co and Si powders was arc-melted in an argon atmosphere to form a button composed of α-Fe2Si5 and ε-FeSi phase. The button was ground under 174μm and mixed with Cu powder. Then they were ground in a conventional ball mill for 360ks or a high energy ball mill for 72ks. β-FeSi2 compacts were obtained by hot pressing of MG powders at 1173K for 1.8ks under 25MPa. It was noted that Cu atom wasn't soluved in the β phase. Thermoelectric power αa increased with increasing Cu concentration and reached at a muximum at x=0.02 (Fe0.98CO0.02 Si2 Cux). The electrical resistivity ρ decreased with increasing Cu concentration. As the result, the power factor α 2/ρ was increased by Cu addition and have the maximum at x=0.02-0.04.View full abstractDownload PDF (1356K) -
Mikio Ito, Kazuhiko Majima, Shigeru Katsuyama, Hiroshi Nagai1995 Volume 42 Issue 2 Pages 156-160
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe preparation of Sm2Fe17Nx permanent magnetic powder whose grain size is finer than the single magnetic domain size of about 300nm was tried by MG for short time (3.6-14.4ks) and the subsequent nitriding treatment. MG for 7.2-10.8ks was effective on the absorption of nitrogen during nitriding treatment and the improvement of magnetic properties. The powders prepared by MG for 10.8ks and the subsequent nitriding treatment at 623K for 7.2-10.8ks showed the coercivity higher than 0.96MA/m (12kOe). The grain size of all powders after MG (even MG for 3.6ks) was about 70nm, and this size is sufficiently fine in comparison to the single magnetic domain size. This fine grain size was also maintained even after nitriding treatment.View full abstractDownload PDF (1433K) -
Kazuhiko Majima, Mikio Ito, Toshitsugu Takeda, Shigeru Katsuyama, Hiro ...1995 Volume 42 Issue 2 Pages 161-165
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe preparation of Sm2Fe17Nx permanent magnetic powder whose grain size is finer than the single magnetic domain size of about 300nm has been tried by mechanical grinding (MG) and the subsequent heat treatment and nitriding. Heat treatment in vacuum reduced the content of oxygen in the speciemen compared with heat treatment in Ar. The nitrided powder after annealed in vacuum was improved in coercivity and the rectangularity compared with the nitrided powder after annealed in Ar. The remanence and rectangularity of the nitrided Sm2.3Fe17Nx specimen after annealed in vacuum were superior to those of the nitrided Sm2.5Fe17Nx specimen after annealed in vacuum. TEM and SEM photographs showed that the vacuum-annealed and nitrided powder after 72ks-MG was composed of mixed grains of 20-100nm.View full abstractDownload PDF (2576K) -
Takekazu Nagae, Masateru Nose, Masaru Yokota1995 Volume 42 Issue 2 Pages 166-170
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSMechanical alloying process and the influence of additives (acetone or ethanol) on the magnetic properties for the mixture of Fe and ZrO2 powders were investigated by mesns of X-ray diffractometer, SEM and VSM. The powder mixtures were milled in vibrating ball mill under Ar atmosphere. In the case of powders without additives, corecive force, He was increased to 16kA/ m with increasing milling time within 100 hours. On the other hand, He of powders with 2% acetone was increased and then decreased with milling time to 7.8kA/m after 170 hours of milling. X-ray diffraction patterns and SEM photographs showed that optimum quantity of addi-tives promote the mechanical alloying of Fe-Zr-O.View full abstractDownload PDF (2875K) -
Eiji Yuasa, Toshimasa Morooka, Makoto Tsunoda, Jun-ichiro Mishima1995 Volume 42 Issue 2 Pages 171-174
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSCu-8mass%Ti-4mass%B alloy powder was prepared by the mecanical alloying (MA) using high energy ball mill. Vacuum hot pressing (VHP) of the MA powder was carried out under various conditions. : the treating temperature range was 673 to 873K, the applied pressure was 425 to 1420MPa and the treating time was up to 18. Oks.
Relation between mechanical properties of the compact and their VHP condi-tions were investigated. Volume fraction of pore in the VHP compact was decreased with increasing the applied pressure and the treating temperature. Rupture strength in VHP compact was increased with increasing the treating temperature and treating time. It was found out that the copper-rich phase forms at the contact region between particles by the VHP particles at 873K, resulting in the high rupture strength. Compact of MA powder in the VHP become denser than the sample sintered after the cold pressing.View full abstractDownload PDF (2768K) -
Hiroshi Kimura, Takeo Oikawa, Hisamichi Kimura, Tsuyoshi Masumoto1995 Volume 42 Issue 2 Pages 175-179
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe pulse discharging resistance-consolidation of mechanically alloyed powders of amorphous Ni50Ti50 and Ti50Al50 under pseudo-isostatic pressure is proposed as a way of near-net-shape forming, in order to obtain full densification of intermetallic compound and to control nano-scaled structure via crystallization. The proposed PHIP technique using a pressure-transmitting medium of spherical graphite powder makes it possible to manufacture a fully densified bulk of intermetallic Ni50Ti50 at applied pressure of 29 MPa by taking advantage of densification via viscous flow. The increase in pressure from 29 to 147 MPa leads to a great decrease from 1470 K to 1200 K in temperature necessary for full densification, conducive to the synthesis of nano-scaled intermetallic Ti50Al50.View full abstractDownload PDF (2999K) -
Toshiji Mukai, Koichi Ishikawa, Yoshihira Okanda, Kenji Higashi1995 Volume 42 Issue 2 Pages 180-184
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSFine grained IN905XL aluminum alloys with five grain sizes between 0.8 and 8.1 μm have been developed by a combination of the mechanical alloying method and a conventional extrusion process in order to investigate the tensile properties at a dynamic strain rate of 2×103 s-1 and a quasi-static strain rate of 1x10-3 s-1. Total elongation at dynamic strain rates is generally larger than that at quasi-static strain rate. Total elongation also decreases with grain size for both strain rates. From an observation with scanning electron microscope (SEM), this trend is due to an initiation of micro-crack at the interface between the matrix and particles finely dispersed near grain boundary region, introduced during mechanically alloying processing, then leads elongation of alloys to small limited values.View full abstractDownload PDF (2644K) -
Yoshiro Arami, Tadashi Koyama, Osamu Iwatsu, Yasuhiko Hashimoto1995 Volume 42 Issue 2 Pages 185-190
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSVarious kinds of Al2O3-dispersion strengthened nickel powders were prepared by mechanical alloying process of carbonyl nickel powder (3μm in average particle size) with a-or γ-Al2O3 powder of about 100 nm each in particle size for various duration in the air atmosphere followed by heat-treatment in a hydrogen atmosphere at various temperatures, and sintera-bility of these powders was investigated.
It was found that the controlling factor which influenced the sintera-bility of oxide-dispersion strengthened nickel powders prepared by mechanical alloying process were the population and the thermal stability of the dislocations induced by mechanical alloying, and the interfacial energy between matrix and oxide which had a little direct contribution to the sinterability of these powders affected that indirectly through its influence on the thermal stability of the dislocations.
In Ni-Al2O3system γ-Al2O3-dispersed nickel powder was superior to α-Al2O3-dispersed one in the thermal stability of the dislocations and con-sequently in sinterability.View full abstractDownload PDF (4315K) -
Keizo Kobayashi, Toshiyuki Nishio, Kimihiro Ozaki, Kenji Miwa1995 Volume 42 Issue 2 Pages 191-195
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSNb-5mass%Al, Nb-8mass%Al(Nb 3 Al), Nb-10mass%Al and Nb-46mass%Al(NbAI 3 ) were synthesized by mechanical alloying (MA) of Nb powder and Al powder using a vibrational ball milling in 35kPa argon gas atmosphere for 720ksec. Though the MA powders were agglomerated, they were solid solutions of Nb and Al in this experimental condition.
Nb-46mass%AI sample, which was prepared by mixing of mechanical alloyed Nb-10mass%Al powder and Al powder, was sintered at 1173K after pressing. The sintered sample was made up of NbAI 3 phase only. As the temperature of reaction between MA powder and Al is higher than the melting point of Al, the synthesis of NbAl 3 from Nb-Al alloy and molten Al by heat treatment can be accomplished by this process.View full abstractDownload PDF (2357K) -
Nobushige Hiraishi, Kazutaka Asabe1995 Volume 42 Issue 2 Pages 196-199
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSIn order to obtain a good hot workability and excellent corrosion resistance in sulphuricacid solution of Ni3Si intermetallic compounds, a process involving a mechanical alloying(MA) method was investigated. However, it was necessary for practicality to improve ductility at room temperature.
This paper reports an investigation to improve ductility of Ni3Si intermetallic compounds at room temperature while maintaining good corrosion resistance. The Influence of Nb and B additions on mechanical properties and sulphuric-acid corrosion resi-stance of these compounds was investigated by MA -hot extrusion -heat treatment method. The results showed that Ni3Si intermetallic compounds with 77.5mol%Ni-20.8mol%Si-1.7 mol%Nb-0.024mol%B composition had high ductility and high corrosion resistance. This compound has more than 4% elongation from tensile test at room temperature. The reason why this compound has high ductility may be due to a high a phase content as well as strengthened grain boundaries, which result from segregated B at the grain boundaries. Moreover, corrosion resistance in sulphuric-acid of less than 0.3mm/year was obtained. This is probably due to an improvment of corrosion resistance in the α- and β- phase in spite of the high α-phase content.View full abstractDownload PDF (4187K) -
Chung-Hyo Lee, Tadashi Asahina, Uichiro Mizutani, Toshiharu Fukunaga1995 Volume 42 Issue 2 Pages 200-204
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSWe applied mechanical alloying to produce molybdenum silicides MoSi2 and Mo5Si3 using a mixture of elemental molybdenum and silicon powders at room temperature. The intermetallic compound MoSi2 have been obtained by ball milling for 100 h, which is transformed to single phase by subsequent heat treatment up to 725°C. The grain size of the MoSi2 powder thus obtained was 19 nm, being approximately four times smaller than that of the commercial alloy. The intermetallic compound Mo5Si3 have been also obtained by MA for 500 h, which is transformed to single phase by heating up to 1000°C. We believe that the retarded MA time for the formation of Mo5Si3 phase is attributed to its complicated crystal structure and large unit cell. The finer grain size in the MA powders is expected to improve room-temperature mechanical properties.View full abstractDownload PDF (1355K) -
Toshimasa Morooka, Eiji Yusas, You Morikawa1995 Volume 42 Issue 2 Pages 205-209
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSStructural change during the mechanical alloying process of a powder mixture which consists of amorphous Ti-43at%Cu alloy and aluminum crystalline powders was investigated by using X-ray diffraction and differential thermal analysis. Changes of structure and hardness in the powder mechanically alloyed for long period with heat-treatment were also investigated. During the mechanical alloying, ternary amorphous phase is formed through interdiffusion of elements over the interface between aluminum and amorphous Ti-Cu alloy powders produced. When the mechanical alloying for longer period was carried out, AlTi phase was formed. In a stage previous to the formation of ternary amorphous phase during the mechanical alloying, the aluminum solid solution dissolved titanium and copper is remained. But the aluminum phase disappeared and Al2Cu3 phase appeared as the heat-treatllent was carried out at 523K, which is lower than the crystallization temperature. Difference of Vickers hardness of the compacts prepared from the powders mechanically alloyed for 72ks and 79.2ks decreased with increasing holding period at 523K.View full abstractDownload PDF (310K) -
Eiji Yuasa, Toshimasa Morooka, Norihide Murasato, Makoto Takano1995 Volume 42 Issue 2 Pages 210-214
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSTitanium and boron powders having a mass ratio of Ti/B = 2/1 were mixed with copper powder in various ratios. They were mechanically alloyed for 72ks by using ball mill. The mechanically alloyed powders with different (2Ti-B) contents were piled up in four layers and then compacted. They were sintered at the temperature range of 873K to 1173K for various times. Volume fraction of pore in the lamellar compact decreases with increasing the sintering time. The degree of pore decrease in the layer of the high (2Ti-B) contents was larger than that in the layer of the low (2Ti-B) contents. The distribution of Vickers hardness, in thickness direction in the sintered lamellar compact changes from stair-like to parabolic with increasing the sintering time at the high temperature. 3-point-bending test of the sintered lamellar compact was carried out. Rupture strength in the bending test in the layer of low (2Ti-B) contents is higher than the layer of high (2Ti-B) contents. Diffusion layer of thickness range of 5 to 80 jim is observed by EPMA at the interface of each layer of the lamellar compact sintered for 108ks at 1173K.View full abstractDownload PDF (2876K) -
Kayo Chatani, Tsunehiro Takeuchi, Toshiharu Fukunaga, Uichiro Mizutani1995 Volume 42 Issue 2 Pages 215-219
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSStudies of approximant crystals have been regarded as playing an important role to deepen the understanding of the quasicrystals. By making use of the fact that mechanical milling (MM ) technique can produce an icosahedral quasi crystalline (QC) phase over the composition range where the cubic 1/1-approximant phase is stable in the Mg-Al-Zn system, we have studied the transformation process from the 1/1-approximant to the quasicrystal by MM and vice versa by the heat treatment. The 1/1-approximant or the so called Frank Kasper Mg39.5Al20Zn40.5 alloy was used as a starting material. We revealed that the transformation into the QC accompanies the reduction in the lattice constant a1/1 of the approximant, while the initially grown QC has the quasilattice constant aR larger than the value eventually reached, which agreed with the calculated value from the a1/1 of the starting approximant. The reverse process is observed in the heat treatment mode. We conclude that the composition partitioning is induced by milling and also by the heat treatment and is responsible for the preferential growth of the Mg-rich thermally stable QC and the reduction in the a1/1 value of the approximant in the MM process.View full abstractDownload PDF (292K) -
Toshio Nasu, Masaki Sakurai, Kenji Suzuki, Yoonsung Cho, Carl C. Koch1995 Volume 42 Issue 2 Pages 220-224
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSA structural study of the ordered B2-CoZr compound during amorphization reaction by high energy ball milling was done using extended X-ray absorption fine-structure (EXAFS) measurement to discuss the micromechanism of amorphization. The ordered B2-CoZr compound powder was prepared by arc melting and annealing. The mechanical milling was done using a vibrating mill. A change in the radial distribution function, provided by the Fourier transform of EXAFS signal, around the Co atom shows that the Zr atom at the first-nearest neighbor around a Co atom is replaced by Cc atom at the second-nearest neighbor; simultaneously the crystalline structure disintegrates and the amorphization reaction occurs.View full abstractDownload PDF (311K) -
Toshimasa Morooka, Eiji Yuasa, Takuya Saitoh1995 Volume 42 Issue 2 Pages 225-228
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSJoining between amorphous Ti-43at%Cu powder, which was prepared by mechanical alloying, and aluminum were attempted following three kinds of conditions. [Process 1]: Pressing into compacts prepared form the amorphous powder against the aluminum ring. [Process 2]: Cold extruding the billet which was filled by amorphous powder between core of aluminum and inside of the can. [Process 3]: Hot extruding of the same billet as the Process 2 (Process 3-1), and hot pressing of extruded samples (Process 3-2). In this study, heating temperature used was lower than the crystallization temperature in order to keep the amorphous state. Characteristic of diffusion joining between amorphous powder and aluminum rod was investigated by using scanning electron microscope and X-ray diffraction. The joining between amorphous phase and aluminum phase in the Process 1 and Process 2 are insufficient, but in the case of Process 3, joining of between the interface of both materials progressed gradually with heating time. Intermetallic compound of Al4Cu9 phase or AlTi3 phase at the interface of amorphous phase and the aluminum phase appears after heat-treatment at 523K for 36 ks in the Process 3-1 and Process 3-2.View full abstractDownload PDF (1435K) -
Toshiharu Fukunaga, Makoto Utsumi, Tamotsu Koyano, Uichiro Mizutani1995 Volume 42 Issue 2 Pages 229-232
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSRecently, it was found that the amorphization of trigonal Se proceeds by the mechanical milling. During the amorphization process a drastic change of the atomic distribution was observed in the 2nd neighbour distance of the crystal. The number of atoms located at the 2nd distance in the crystal was reduced 4 to 0. Since the 2nd nearest neighbour corresponds to the inter-chain molecule correlation in the trigonal Se, it can be concluded that trigonal Se is amorphized by destructing the connection of adjacent chain molecules during the milling process. Therefore, the amorphous Se can be regarded as being built up only of chain molecules. Moreover, it was found that the amorphous Se structurally easily relaxed even below the glass transition temperature and partly crystallized after annealing at 30°C for 3months.View full abstractDownload PDF (255K) -
Noriaki Ohba, Hideki Kondo, Tsuyoshi Arakawa1995 Volume 42 Issue 2 Pages 233-236
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSCrystalline powders of Pd and Si or Zr in the composition ratio varying from Pd:Si (Zr) = 1:2 to 2:1 were mechanically alloyed by a laboratory ball mill in an inert atomosphere. The formation of Pd silicides (Pd2 Si and PdSi) have been recognized at the beginning of milling. On the other hand, in the Pd-Zr system amorphous alloys were obtained as well as the other many systems. Definite exothermic crystallization peak was not measured by differential thermal analysis (DTA) in the temperature range from 298 to 1073K. This result shows that the crystallization enthalpy of amorphous Pd-Zr alloy powders is very small.View full abstractDownload PDF (209K) -
Yuzo Okudaira, Yoshitaka Kurihara, Hideyuki Ando, Munetake Satoh, Kei ...1995 Volume 42 Issue 2 Pages 239-244
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSSound absorption coefficients of various powder beds comprised of binary powder mixtures were measured using an acoustic tube, and the longitudinal elastic coefficients of the powder beds were obtained from the absorption peak frequencies. It was found that the longitudinal elastic coefficient of the powder mixture bed in an almost naturally packed state can be estimated from the respective longitudinal elastic coefficient and volume ratios of the constituent powder materials. This indicates the possibility of designing new sound-absorbing materials to suit the characteristics of the noise source.View full abstractDownload PDF (3000K) -
Tadao Kaneko, Mieko Sakurai, Osamu Nittono, Hiroshi Shimizu1995 Volume 42 Issue 2 Pages 245-248
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSAn apparatus was constructed to nitrify small mettallic sintered parts by using a hollow-cathode discharge plasma method. A stainless steel basket, which contains a sintered part to be nitrified, is potentially grounded and serves as hollow-cathode electrode. Hollow-cathode plasma was produced by supplying the positive voltage to the anode. In this study sintered carbon iron and stainless steel were used as testing specimens. It was shown that an effective nitrifying took place by controlling the total pressure of nitrogen and hydrogen gas and applied voltage.View full abstractDownload PDF (1461K) -
Mechanism of Grack PropagationEiichi Sentoku, Tsutomu Naka1995 Volume 42 Issue 2 Pages 249-252
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSMachinable ceramics consisting of fluor-phlogopite can be easily machined using conventional metal working equipment and tools. In recent years, ceramic parts require precise machining. The formation of cracks has a direct effect upon the machined surface.
The purpose of this paper is to study the mechanism of crack propagation in machinable ceramics. The investigation of the behavior of cracks in ceramics was carried out using a simple model of the finite element method (FEM).
The main results obtained are as follows: (1) The pattern of crack propagation are type (A) of straight path in the mica and type (B) of detour path to boundary glass and mica. (2) The deflection and the branching of the crack are most influenced with the ratio of the maximum fracture stress of the mica to that of the glass. (3) Assuming that the propagation length of crack is proportional to the fracture energy, this energy of crack type B to type A increases to about 60% with the ratio of propagation length at 1.66 times.View full abstractDownload PDF (2311K) -
Hiroshi Yamamoto, Hiroaki Take1995 Volume 42 Issue 2 Pages 253-258
Published: February 15, 1995
Released on J-STAGE: November 19, 2010
JOURNAL OPEN ACCESSExperiments were carried out to investigate the effect of Na2O addition after semisintering treatment on magnetic properties of anisotropic BaO2ZnO8Fe2O3 magnets. It was found that the magnetic properties of Ba-Zn system W-type ferrite were improved by the addition of Na2O after semesintering treatment. The optimum condition of making magnets and some properties of typical specimens are as follows : composition BaO⋅2ZnO⋅8Fc2O3 in addition with 1.5wt% Na2O ; semisintering condition 1275°C for 1.Oh in air ; sintering condition 1250°C for 0.5h in air ; magnetic and physical properties are Jm=0.398 T, Jr=0.360 T, HcJ=103.6 kA/m, HcB=101.8 kA/m, (BH)max=19.9 kJ/m3, Tc=357°C, HA=1012 kA/m, KA=2.01x105J/m3View full abstractDownload PDF (1566K) -
Toshiji Mukai, Kenji Higashi, Atsumichi Kushibe, Mamoru Mabuchi, Shinj ...1995 Volume 42 Issue 2 Pages 259-263
Published: February 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe compressive behaviors at strain rates from 4x10-6 to 1x10-2 s-1 at temperatures from 1373 to 1448 K were characterized to investigate the influence of grain size for powder metallurgically processed TiAI intermetallics with fine grained structures of about 18 μm in size and ingot metallurgically processed TiA1 with coarse grained structures of about 380μm. For coarse and fine grained intermetallics of TiA1 at higher stresses, stress exponent of about 4 is found and the rate controlling deformation may be a diffusion controlled dislocation process. At intermediate stresses for the fine grained TiA1, a stress exponent of about 2 is found, and the rate controlling deformation is proposed to be grain boundary sliding. In two different grained intermetallics, furthermore, the measured activation energy from 343 to 370 kJ/mol is obtained.View full abstractDownload PDF (272K)
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