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Volume 38, Issue 7
Displaying 1-29 of 29 articles from this issue
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Takashi Sakamoto1991 Volume 38 Issue 7 Pages 839-843
Published: September 25, 1991
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSIt is known that an addition of small amount of Ni powder in Mo powder compact is effective to increase the sintered density.
This paper describes the sintering characteristics of Mo-(0-3.0)%Ni powder compacts with the addition of B, NiB, MoB or C, when sintered at 1200 or 1300°C for 3.6 ks in vacuum.
The results are as follows:
(1) B and C powders are both effective on densification.
(2) The densification is considered to be due to the liquid phases formed during sintering, this being examined by DTA and SEM.
(3) The process of densification is verified by TMA.
(4) NiB and MoB powders are also effective, but the bending strength is lower than that of the B addition.View full abstractDownload PDF (2624K) -
Hidenori Kuroki, Koji Komatsu, Tokuhiko Mishida1991 Volume 38 Issue 7 Pages 844-848
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSPowders coarser than and similar to those for most metal injection molding processes were compared
to each other. The 13μm and 7μm water-atomized SUS316L powders were pressed so as to form compacts 10 mm in diameter and about 7 mm in height with a low density of about 4.85 Mg/m3 which is rather close to that of the injection molded samples. They were sintered at 1373-1673K for 60 min in hydrogen.
The 7μm powder densified with the disappearance of small pores and the transitional growth of large pores as the sintering temperature rose, though the 13μm powder changed the pores into rounded shapes at low temperatures, and quickly reduced the total porosity at temperatures above 1573K. At 1623K or above, the difference between the pore structures of these powders almost disappeared. Any differences in tensile strength and elongation of these powder samples prepared actually by metal injection molding, also disappeared at 1623K.
The shrinkage of unidirectionally pressed compacts by sintering and that by cold isostatic pressing showed a similar anisotropy, giving a larger shrinkage in the lateral direction in both cases.View full abstractDownload PDF (346K) -
Hiroshi Horiguchi, Toshiro Terakawa, Hideaki Baba, Katuhisa Takane1991 Volume 38 Issue 7 Pages 849-853
Published: September 25, 1991
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSAs the raw material of MIM (Metal Injection Molding), carbonyl and atomized iron powders have been utilized.
In stead of those expensive powders, pulverized iron powder was developed and the possibility of application for MIM was checked. The results are as follows:
(1) By a globular treatment, the fluidity of the powder is improved in injection molding process.
(2) As concerns sintered compacts, the relative density is over 95%, and the tensile strength and elongation obtained are satisfactory.
(3) When a debinded compact contains much oxygen, a low temperature reduction is effective for increasing sintered density.
(4) Furthermore, the reduction is effective for carbon control of sintered compact, and a high carbon compact can be manufactured easily.View full abstractDownload PDF (4114K) -
Hidehito Fujiuchi, Koji Hayashi1991 Volume 38 Issue 7 Pages 854-857
Published: September 25, 1991
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe effect of test temperature on the hardness (HV) of fine-graind sintered compacts with the average crystal grain size of 0.10-0.35 μm, which were prepared from ultrafine powders of 0.02 μm, was investigated for Fe, Co, Ni, Fe-Co, Fe-Ni, Co-Ni and Fe-Co-Ni systems. The test temperature dependence of Hv for the Fe sintered com-pact was compared with those of medium or coarse-grained sintered compacts of 0.82-3.5 μm.
The results obtained were as follows: (1) The order of Hv observed at room temperature among the alloy systems did not change in general at the higher test temperatures. (2) The Hv of Fe fine-grained compacts decreased sharply at about 500 K, which was much lower than that (about 800 K) for coase-grained compacts of 3.5 μm. This was attributed to the fact that creep deformation easily occurs even at such low temperatures for fine-grained compacts.View full abstractDownload PDF (281K) -
Masatomo Kamada, Shinya Ozaki, Youichi Tokunaga1991 Volume 38 Issue 7 Pages 858-863
Published: September 25, 1991
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSPhosphorus and 0.1 wt% carbon were added to SUS304L powder compacts in order to strengthen the P/M austenitic stainless steels. Effects of phosphorus content on the sintering and age hardening behavior were in-vestigated, in association with the tensile properties of the compacts. The results are summarized as follows:
Phosphorus can dissolve in austenitic matrix up to about 0.45 wt% at 1523 K. In the compacts containing over 0.45 wt% of phosphorus, a liquid phase is formed through eutectic reactions and remains during the sintering. This results in the densification of compacts and the pore rounding.
Tensile strength of as-sintered compacts increases with an increase in phosphorus content to reach the peak of 470 MPa at 0.6 wt% P, because of the solid solution hardening and the promotion of sintering. Phosphorus addition over 0.6 wt% produces a large amount of eutectic microstructure which affects negatively to the improvement of strength.
Tensile strength of 0.6 wt% P compact increases to 590 MPa by the aging at 1023 K for 30 ks. The relation between porosity (ε) and strength ratio of porous compacts to full density compact (σ/σ0) is expressed by (σ/σ0) =(1-ε)/(1+6ε) for the 0.6 wt% P compacts aged in optimum conditions.View full abstractDownload PDF (5546K) -
Takeshi Kaneko1991 Volume 38 Issue 7 Pages 864-871
Published: September 25, 1991
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThis report describes the results of investigations on the improvement of characteristics of tungsten heavy alloys which were produced with addition of suitable amount of Co (with Ni/Fe ratio of about 2.0) to basic composition of W-Ni-Fe, and an optimum amount of Co addition obtained. The mechanical properties at room temperature of the (91.8-93.4 wt% W) alloys increased with increasing Co content and attained a maximum with Co content of about 1.5 wt%, while the 95.4 wt% W alloys attained a maximum with Co content of about 0.5 wt%.
In the alloys with (addition of) suitable amount of Co, smaller dihedral angle between W-W grain and better "Wettability" were obtained, and it was made clear that those effect resulted in homogeneity of alloys, and the improved mechanical properties.
The SEM photographs of the fracture surfaces show that Co content alloys strengthen mainly the interface between W-binder phase boundaries and W-W grain boundaries.View full abstractDownload PDF (3489K) -
Won-Seung Cho, Koji Hayashi1991 Volume 38 Issue 7 Pages 872-878
Published: September 25, 1991
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe effects of contents of Y2O3 sintering aid (4-14 mol%) and SiC whisker (SiC(w): as-received one (5-30 vol%) and sieved one (20 vol% only)) on the transverse-rupture strength and fracture toughness of SiC(w)/Si3N4-Y2O3-6 mol%Al2O3 composite ceramics were investigated, paying attention to the changes in the grain boundary phase, the size of acicular Si3N4 grains and the fracture source.
Results obtained were as follows: (1)Both the strength and toughness of the composites with 20 vol% as-received-and sieved-SiC(w) became a maximum at 8 mol%Y2O3, in the same way as the monolith. This was con-sidered mainly due to the largest acicular Si3N4 grain size and partly to the appearance of grain boundary phase of 5Y2O3⋅Si3N4⋅Al2O3 at such a Y2O3 content. (2)With increasing SiC(w) content, the strength decreased in spite of the increase in the toughness, which was attributed to the increase in the size of microstructural defects as a fracture source. (3)In spite of higher strength level of the specimens than those in the other reports, the fracture sources were large Si3N4 aggregate of 10-50 pm in the monolith, SiC(w) aggregate of 60-190 μm in the composite with as-received SiC(w) and SiC(w) aggregate of 18-80 μm in the composite with sieved SiC(w).View full abstractDownload PDF (9820K) -
Tamotsu Ueyama, Takashi Yamamoto1991 Volume 38 Issue 7 Pages 879-886
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe effects of the W metallizing condition and silver brazing condition on the bonding reliability of the nail head lead pins of the multilayer ceramic substrates manufactured by co-firing was examined. High bonding strength by the silver brazing to the W metallized layer was obtained when the W metallizing layer was 23 μm thick or thicker and the quantity of the silver solder used was 0.24-0.38 mg/mm2 and the silver brazing temperature was 820-840°C. The bonding strength by the silver brazing was decreased after the brazed parts were heat-treated at 900°C. The cause of the degradation of the bonding strength was that the silver solder permeates into the W metallized layer and destroys the network of the W in that layer.View full abstractDownload PDF (6698K) -
Hideaki Yagi, Takehiko Saiki1991 Volume 38 Issue 7 Pages 887-892
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSHumidity sensors using various NASICON materials were experimentally produced by a thick film printing method. Among the NASICON materials, a humidity sensor using Na4Zr2Si3O12 material showed comparatively lower resistance in low humidity. The relation between a logarithm of its resistance and relative humidity was almost linear and showed nonhysteresis (2M-10kΩ in a range of 20-90%RH). Also, the humidity sensor using Na4Zr2Si2O12 in comparison with one using a usual NASICON was improved on the stability of a long term and durability in various environment tests.View full abstractDownload PDF (1194K) -
Shigetaka Wada1991 Volume 38 Issue 7 Pages 893-894
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe effect of the fracture toughness of impact particles on the erosive wear of ceramics was examined. Six kinds of Al2O3 abrasive particles, which were almost the same in size, figure and hardness, but different only in fracture toughness, were used as impact particles. Sintered Si3N4, Al2O3 (HA9O) and glass were used as target materials. Irrespective of the target materials, the erosive wear rate was qualitatively proportional to the fracture toughness of the impact particles.View full abstractDownload PDF (96K) -
[in Japanese]1991 Volume 38 Issue 7 Pages 896
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (79K) -
Akihisa Inoue, Tsuyoshi Yamamoto, Tsuyoshi Masumoto1991 Volume 38 Issue 7 Pages 897-902
Published: September 25, 1991
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe influence of applied pressure on the structural relaxation, glass transition, crystallization and consolidation for an amorphous phase was examined by using a typical glassy Pd48Ni32P20 alloy in a spherical powder or a ribbon form. The Pd-Ni-P alloy was chosen because of the existence of a wide supercooled liquid region in the temperature range below crystallization temperature (Tx). The relaxation and crystallization are significantly suppressed by the application of compressive load, presumably because of the increase in viscosity and the decrease in diffusivity. As a result, the pressing at a high temperature of 0.97Tx is required to produce an amorphous bulk with high relative density. Furthermore, an intermediate annealing between pressings was found to be effective for the reduction of the enhanced viscosity. The multi-stage pressing treatment consisting of pressing and annealing enabled to produce a highly dense amorphous bulk even at a relatively low temperature near Tg.View full abstractDownload PDF (1555K) -
Eugene Ivanov, Boris Bokhonov, Irina Konstanchuk1991 Volume 38 Issue 7 Pages 903-905
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSMechanical alloying (MA) was used to obtain quasicrystalline; phases Mg3Zn5-xAlx (x=2-4) and i-Mg32Cu8Al4 starting from the elementary metal powders.Mechanical disordering(MD) of cubic Frank-Kasper (F-K) phases such as Mg32(Zn, A1)49 lead to formation of relative quasicrystalline structures as well.The X-ray diffraction patterns of i-phases are identical to those obtained by rapid quenching. SAD patterns of both MA and MD samples demonstrated 2, 3, 6, and 5-fold symmetry pictures.There are ten sets of Bragg spots with angles between them 36°. The values of the interplanar distances in i-Mg32(Zn, Al)49 are d1=0.141nm, d2=0.228nm, d3=0.369nm, d4=0.597nm, dn=dn-1t, where t=(1+51/2)/2.The cubic phases Mg32(Zn, Al)49 and Mg32(Cu, Al)49 are F-K structures with local 5-fold symmetry units.The icosa-hedral structure can be described in terms of cubic F-K phase containing discli-nations.The MD of F-K phases lead to progressive broadering of X-ray peaks due to the structural, defects arising in cubic lattice and the icosahedral phases were formed apparently due to the formation of disclination network during MD.View full abstractDownload PDF (203K) -
Nobuo Asahi, Masaaki Oyama1991 Volume 38 Issue 7 Pages 906-909
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSAg30Dy70 alloy was mechanically alloyed from pure crystalline Ag and Dy powders by high energy ball milling (Fritsch "Pulverisette 7") with the speed settings 7 or 3 in an argon atmosphere. The alloying process was investigated by X-ray diffraction, optical microscopy and differential scanning calorimetry.
In the first milling stages, the Ag and Dy powders have a well-aligned layered microstructure. This microstructure is typical for mechanical alloyed specimens during the early stages of milling and gets finer with increasing milling time. At this stage intermetallic compound AgDy has obtained. After 200 h of milling, the X-ray diffraction peaks of AgDy and Dy powders have hardly changed in intensity and the broad peak characteristic of an amorphous Ag30Dy70 powder was not produced by mechanical alloying from crystalline elemental powders.View full abstractDownload PDF (1487K) -
Junji Kuyama, Keiichi N Ishihara, Paul Hideo Shingu1991 Volume 38 Issue 7 Pages 910-913
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSMechanical alloying (MA) of Fe-Mo binary system was performed by the low energy ball mill method. Elemental Fe and Mo powders were ball-milled up to 1000h. We characterized the reaction products by X-ray diffraction analysis, high resolution electron microscopy (HREM), and EDX analysis. From the X-ray diffraction patterns of MA powders, it was found that an amorphous phase was obtained in the composition of 30-50at%Mo and single bcc phase was obtained in the composition of 10-20at%Mo and 60-90at%Mo. The amorphization started from an early stage of MA and the amorphous region extended as MA continued. HREM investigation of Fe-30at%Mo and Fe-50at%Mo revealed that fine grains whose particle sizes are several nano-meters exist in the amorphous matrix. By the quantitative analysis by EDX, these grains were found to be Mo rich in composition.View full abstractDownload PDF (2959K) -
Young Ho Paark, Katsuhisa Yamauchi, Hitoshi Hashimoto, Ryuzo Watanabe1991 Volume 38 Issue 7 Pages 914-919
Published: September 25, 1991
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSTi/Al powder mixture(Ti:Al=1:1) was mechanically alloyed by vibratory ball milling to analyze the action of milling ball size on the formation of an amorphous phase, by using X-ray diffraction analysis, electrical resistivity measurement, microhardness measurement, optical microscopy, SEM and TEM. As a result, the size of milling balls was found to play a decisive role in the amorphous phase formation. The electrical measurement made for the first time on the mechanically alloyed Ti/Al powder to monitor the phase transformation was found to catch successfully the formation of the amorphous phase and its crystallization during milling. TEM observation on the amorphous powder particles revealed that nano-sized crystalline intermetallic compounds were precipitated in the amorphous particles, which suggests that for the formation of the perfect amorphous phase it is of great importance to use milling balls smaller than 4.76mm.View full abstractDownload PDF (6367K) -
Osamu Kimura1991 Volume 38 Issue 7 Pages 920-924
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe ultrafine Mn-Zn ferrite (MnO)0.37 (ZnO)0.10(Fe2O3)0.53 has been prepared by the amorphous citrate process. Extra pure manganese metal (99. 95%), zinc metal(>99. 99%) and iron metal (>99. 99%) are dissolved into 6N HNO3 to prepare stoichiometric aqueous solution of manganese nitrate, zinc nitrate and ferric nitrate. Nitrate salts are avoided as starting materials, since they are strongly hygroscopic in nature. The nitrate solution is mixed with citric acid and ethylene glycol in a uniform solution. The water and nitric oxides are evaporated at around 90°C and ethylene glycol is dried at aruond 120°C to yield a solid precursor material. The precursor is fired to high temperature to form the desired compound. The decomposition mechanism is studied with thermogravimetric analysis, differential thermal analysis and X-ray diffraction. Also, magnetic properties and BET surface areas are measured for heat-treated powders.View full abstractDownload PDF (1550K) -
Osamu Kimura, Hiroshi Ochiai1991 Volume 38 Issue 7 Pages 925-929
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe high-Hc ultrafine hexaferrite SrO-n(Fe2O3)(n=5.4, 5.5, 5.8, 6.0)has been prepared by the amor-phous citrate process. An extra pure iron metal(>99.99%) and a pure strontium carbonate(99.7%) are dissolved into 6N HNO3 to prepare stoichiometric aqeous solution of strontium nitrate and ferric nitrate. Nitrate salts are avoided as starting materials, since they are strongly hygrosc-opic in nature. The nitrate solution is mixed with citric acid and ethyleneglycol in a uniform solution. The water and nitric oxides are evaporated at around 90 °C and ethyleneglycol is dried at around 120 °C to yield a solid precursor material. The precursor is fired to high temperature to form the desired compound. The decomposition mechanism is studied with thermogravimetric analysis, differential thermal analysisand X-ray diffraction. Also, magnetic properties and BET surface areas are measured for heat-treated powders. Coercive force He reaches 6700 Oe at 10KG for the powder obtained by firing the precursor in air to 700 °C for lhr and nearly pure-phase strontium hexaferrite powders are formed at 1000 °C for lhr.View full abstractDownload PDF (1367K) -
Masahiro Oguchi, Yoshio Harakawa, Yoichi Shimizu, Akihisa Inoue, Tsuyo ...1991 Volume 38 Issue 7 Pages 930-933
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSAmorphous Co70.3Fe4.7Si10B15 powders were produced by a two-stage quenching technique consisting of high-pressure gas atomization followed by centrifugal spinning. The amorphous powders have a flaky morphology with a disk or an ellipsoidal shape. The thickness is as small as 1 to 3 μm and the dimension along the longitudinal direction is 25 to 300 μm leading to large aspect ratios of about 20 to 300. The composite consisting of the flaky amorphous powders embedded in phenol resin exhibits significantly anisotropic magnetic properties because of a well developed arrangement of the flaky powders along the direction perpendicular to the hot-pressing direction. Judging from the combined characteristics of the unique powder morphology and the magnetic properties inherent to the Co-based amorphous phase, the flaky amorphous powders are concluded to have a further enhanced engineering potentiality.View full abstractDownload PDF (2694K) -
M.Sherif El-Eskandarany, Hiroshi Suzuki, Kiyoshi Aoki, Kenji Suzuki1991 Volume 38 Issue 7 Pages 934-939
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSPreviously published calorimetric study of amorphous Ta-50 at.%Al alloy powders is complemented by structure and morphological studies. The alloy powders were prepared by mechanical alloying (MA) from pure elemental powders of Ta and Al. The alloy powders have been characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy. The results have shown the MA process takes place through three stages, that is to say, agglomeration, amorphization and homogenization stages.View full abstractDownload PDF (8648K) -
Toshiharu Fukunaga, Eiji Ishikawa, Uichiro Mizutani1991 Volume 38 Issue 7 Pages 940-943
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSCr and Fe elemental powders at 7:3 atomic propotion were milled in a vibrational ball mill under N2 gas atmosphere. The concentration of N atoms in the Cr0.7Fe0.3-N powders increased with increasing MA time and approached to about 15at%N after 320 hours of milling. The amorphization was observed by X-ray diffraction and DSC measurements.
RDF(r) shows that the 2nd nearest neighbor atoms in BCC crystal preferentially moved out of their positions during the amorphization process and the 1st nearest neighbor distance between metal atoms increases with increasing the milling time. The nearest coordination number around a metal atom within about 3.3 A decreases from 14 to 12.5 atoms while the amorphization proceeds. These results definitely tell us that the octahedral unit in a BCC structure is destroyed and is transformed into the tetrahedral unit during the amorphization process. An increase in the metal-metal distance of the 1st nearest neighbor with increasing nitrogen content can be interpreted by the penetration of a nitrogen atom into a polyhedron formed by metal atoms.View full abstractDownload PDF (242K) -
Junji Saida, Akihisa Inoue, Tsuyoshi Masumoto1991 Volume 38 Issue 7 Pages 944-947
Published: September 25, 1991
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSAmorphous ultra-fine powders in (Fe, Co, Ni)-B systems were prepared by a chemical reduction method using KBH4. The powders have a spherical morphology with diameters ranging from 20 to 50 nm. The boron concentration is in the range of 25 to 35 at.% and chemical composition of the metal elements can be controlled by changing the concentration of metal ions. Crystallization temperature (Tx) and heat of crystallization for an ultra-fine Fe50Ni22B28 powder agree with those obtained for the amorphous alloy with the same composition prepared by melt spinning. The reaction process consists mainly of the process of preparing Me2B and Me (Me=Fe, Co, Ni). Furthermore, the amorphous powders were found to be consolidated to a fully dense amorphous bulk by uniaxial pressing at temperatures below Tx. Their densities are almost equal to those of the corresponding arc-melted crystalline powders. Hardness values of the hot-pressed compacts are considerably lower than those of the melt-spun amorphous ribbons with the same composition.View full abstractDownload PDF (3410K) -
Yoshihito Kawamura, Akihisa Inoue, Tsuyoshi Masumoto1991 Volume 38 Issue 7 Pages 948-952
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSHigh-strength Mg-Cu-Y amorphous alloys with significant supercooled liquid region have attracted attention as a structural light metal. The future application of the new alloys seems to be dependent on the development of a technique of consolidating the amorphous powders to an amorphous bulk. The effects of applied pressure, pressing temperature and flow strength of an alloy on the densification of amorphous powders by uniaxial warm pressing were examined for an amorphous Mg65Cu25Y10 alloy with a wide supercooled liquid region of 67K.
The amorphous alloy with a distinct glass transition phenomenon is easily consolidated near Tg, especially above Tg, and the minimum consolidation pressure required to obtain an amorphous bulk with true density is about four times as high as the flow strength of the alloy at the consolidation temperature. As the pressing temperature approaches Tg the effect of applied pressure on the densification decreases. The amorphous Mg65Cu25Y10 bulk with true density was obtained even at a small pressure of 0.2GPa, when the pressing temperature is 10K higher than Tg. The significant temperature dependence is attributed to the drastic decrease in the flow strength of the amorphous alloy by the glass transition.View full abstractDownload PDF (4386K) -
Katsumasa Ohtera, Takeshi Terabayashi, Hidenobu Nagahama, Akihisa Inou ...1991 Volume 38 Issue 7 Pages 953-956
Published: September 25, 1991
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSAluminium-based amorphous powders of A185Ni5Y10 and A188.5Ni8Mm3.5 were produced by high-pressure gas atomization. Since the amorphous A185Ni5Y10 alloy exhibits the glass transition before crystallizaion, the extrusion of the A185Ni5Y10 amorphous powder was performed at temperatures below crystallization temperature(Tx). The resulting extruded bulk consists mainly of an amorphous phase and the compressive strength is as high as 1052MPa. On the other hand, the amorphous A188.5Ni8Mm3.5 powder without glass transition was extruded at temperatures above Tx and the highest tensile strength reached 94OMPa for the extruded bulk with a finely mixed structure of Al11(Ce, La)3 and Al3Ni embedded in an aluminium matrix.View full abstractDownload PDF (1539K) -
Minoru Umemoto, Tsuyoshi Itsukaichi, Isao Okane, Yasutoshi Mizuno, Ter ...1991 Volume 38 Issue 7 Pages 957-962
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSMechanical alloying is applied to prepare Sm2Fe17Nx permanent magnet. Starting from elemental powders, the formation of hard magnetic phase of Sm2Fe17Nx by milling in a horizontal ball mill and a successive solid-state reaction was studied. The effect of starting composition of powder on product phase was first investigated. At as milled condition powder was found to consist of α-Fe and Sm-Fe alloy amorphous phases when Sm content is less than 19 at% and consist of α-Fe and SmFe2 phase when Sm content is 26 at%. After heating and nitriding treatments pow-der was found to consist of α-Fe and Sm2Fe17Nx when Sm content is less than 15 at% and consist of α-Fe and SmN when the Sm content is 26 at%. When Sm content was 19 at%, nitrided MA powder consists of mostly Sm2Fe17Nx phase. The effect of milling time was studied for the powder of starting composition of Sm19Fe81. When powder was milled longer than 180ks, almost single phase of Sm2Fe17Nx was formed after nitriding. Coercivity was observed to increase linearly with logarithm of milling time from around 72ks and reached to 1200kA/m after 360ks of milling. This high value of coercivity was cosidered to be obtained by ultra fine grain size of Sm2Fe17Nx produced by ball milling and heat treatment.View full abstractDownload PDF (1558K) -
Shinya Shiga, Tsuyoshi Itsukaichi, Minoru Umemoto, Isao Okane1991 Volume 38 Issue 7 Pages 963-966
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSElemental powders of Al and Ni with the composition of Al25Ni75 was mechanically alloyed in an Ar gas atmosphere for various periods using a horizontal ball mill. A single phase of Ni solid solution with Al super saturation was obtained by a long time milling. This Ni solid solution transformed into AINi3 compound (Ll2:ordered FCC) at around 700K with the enthalpy of 4.6kJ/mol. The hardness of hot-pressed compacts prepared from MA powders was higher than that of melted and solidified, irrespective of the MA time. The hot pressed compacts of MA powders showed compositional inhomogeneity when powders were milled shorter than 36ks and showed voids when powders were milled longer than 360ks. The suitable MA time for sintering was in the range between 72 and 180ks.View full abstractDownload PDF (2872K) -
Shinya Shiga, Tsuyoshi Itsukaichi, Minoru Umemoto, Isao Okane1991 Volume 38 Issue 7 Pages 967-970
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSElemental Powders of Al and Ni with the composition of Al50Ni50 was mechanically alloyed in an Ar gas atmosphere for various periods using a horizontal ball mill. A single phase of AM compound (B2:ordered BCC) was synthesized by milling longer than 360ks. The powder particle size was substantially decreased to about 0.5 μm in diameter by MA associated with the formation of AlNi compound. The MA powders were hot-pressed under the condition of 150MPa at 973K for 1.8ks. The hot-pressed compacts showed compositional inhomogeneity when powders were milled shorter than 72ks. When MA time is longer than 180ks, the unsintered region appeared in the hot-pressed compact and the area increased with the increase in MA time. The powder milled for 1800ks did not sinter at all. The hardness of hot-pressed compacts showed maximum of 500Hv at MA time of 18ks and reduced gradually with MA time. The suitable MA time for sintering was considered to be around 100ks.View full abstractDownload PDF (2956K) -
Shinya Shiga, Tsuyoshi Itsukaichi, Minoru Umemoto, Isao Okane1991 Volume 38 Issue 7 Pages 971-975
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSElemental powders of Al and Ni with the composition of Al75Ni25 was mechanically alloyed in an Ar gas atmosphere for various periods using a horizontal ball mill. A single phase of disordered AlNi structure (BCC) was obtained by milling of 1800ks. This BCC structure transformed into Al3Ni compound (DO20) at around 600K. The hot-pressed compacts of MA powders showed compositional inhomogeneity and voids produced by isothermal solidification when powders were milled shorter than 72ks and showed well sintered structure when powders were milled longer than 180ks. The hardness of hot-pressed compacts prepared from MA powders milled between 36ks and 360ks reached at around 750Hv. The suitable MA time for sintering was considered to be between 180ks and 360ks.View full abstractDownload PDF (4073K) -
Shinya Shiga, Takayuki Norimatsu, Tsuyoshi Itsukaichi, Minoru Umemoto, ...1991 Volume 38 Issue 7 Pages 976-980
Published: September 25, 1991
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe structural change in Al75Ni25 powder during MA and MG was studied using SEM, X-ray diffraction and DSC. MA was carried out for the mixture of elemental Al and Ni powders and MG was done for the powder of Al3Ni intermetallic compound prepared by arc melting. In both MA and MG processes, the major end product was found to be disordered AlNi (BCC) which was identified by X-ray diffraction. DSC and x-ray diffraction analysis showed that the disordered AlNi phase transformes directly to Al3Ni intermetallic compound by heating. It was noted that the transformation temperature of disordered AlNi structure to Al3Ni compound in MG powder is higher than that of MA powder. The amount of exothermic heat associated with this transformation in MG powder (1.0kJ/mol) was found to be smaller than that of MA powder (2.5kJ/mol). This difference may arise from the fact that in the case of MG powder Al3Ni compound still partially remains even after heating up to 973K.View full abstractDownload PDF (2428K)
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