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Volume 23, Issue 3
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[in Japanese]1976 Volume 23 Issue 3 Pages 77-84
Published: April 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (512K) -
Junzô Shimoiizaka, Katsuto Nakatsuka, Ryôji Chûbachi ...1976 Volume 23 Issue 3 Pages 85-89
Published: April 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSFormation of Ni-Zn ferrite by wet method, and the change of magnetic characteristics arised from heating of the coprecipitates were examiried.
The coprecipitates were prepared by adding alkaline solution into the constituent metal ions solution, and then aged at various temperature. Below 120°C, the products were ultra-fine spherical particles of about 90A in diameter. Above 120°C, some of them grew into cubic particles. The products formed in the latter condition were constructed of superparamagnetic and ferromagnetic particles. When those were heated at 800°C in air, the superparamagnetic particles disappeared. The Curie temperature of Ni-Zn ferrite obtained by this method were higher than that by ceramic method. When the coprecipitates were heated at 1000°C, the Curie temperature of it was the same value as that by ceramic method.View full abstractDownload PDF (1574K) -
Osamu Yamaguchi, Tadashi Yasuhara, Kiyoshi Shimizu1976 Volume 23 Issue 3 Pages 90-95
Published: April 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe formation and sintering of PbTiO3 containing a small amount of PbO-TiO2-Al2O3-SiO2 glass were investigated by means of X-ray diffraction, thermal analysis, electron microscopy, dilatometry and the measurement of isothermal shrinkage.
The rate of formation of PbTiO3 from PbO and TiO2 containing 0.01 wt % glass was determined. Reaction isotherms were best described by the Jander's equation. The apparent activation energy of the reaction was about 50 kcal/mol.
The PbTiO3 powder was mixed with 0.005 or 0.01 wt % glass powder, pressed into pellets at 1 ton/ cm2, and heated at 1100-1200°C for 1-2 hr in various atmospheres. All the sintered specimens had grain size of 0.5-2μ and a bulk density of 7.23-7.63g/cm3. The density of 7.63 g/cm3 was obtained by heating at 1120°C for 1 hr in the oxygen atmosphere. The order of the sinterability in various atmospheres of PbTiO3 contained the glass was O2>PbO>air>N2. This fact suggests that the sintering of PbTiO3 is affected by partial pressure of oxygen.
The mechanism of initial sintering in PbTiO3 contained 0.01 wt % the glass was studied by isothermal shrinkage at temperatures ranging from 900°to 1050°C in air and oxygen. Time dependence of the shrinkage was consistent with the mechanism based on grain boundary diffusion in air and volume diffusion in oxygen, and the activation energies for sintering processes were about 46 kcal/mol and 76 kcal/ mol, respectively. Comparison our data with others suggests that the diffusion of Pb2+ in air and Ti4+ in oxygen control the initial sintering.View full abstractDownload PDF (1639K) -
Yoshikazu Suzuki1976 Volume 23 Issue 3 Pages 96-103
Published: April 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe effect of pores on the mechanical properties of high density sintered iron sheets has been examined by means of tensile test and direct observation on the surface of the specimen during tensile test in the scanning electron microscope. As the test pieces used, the high density sintered iron sheets were prepared by direct powder rolling or by laminating the sheets. The volume fraction and the shape of pores, and the distribution of pore size were changed by sintering at 850°C for 60 min, cold-rolling within the range of 44% to 92%, and annealing at 700°C for 60 min in hydrogen.
The following results were obtained. (1) In an atomized iron sheet, which was sintered and cold rolled at about 50% (total reduction) and then annealed, weakly bonded grain boundaries were observed, which seemed to be composed of pores. Then, these grain boundaries play a role on the nucleation and propagation of cracks in the iron sheet during tensile tests. (2) After laminating atomized iron powder sheets with carbonyl iron powder, these sheets were sintered, cold-rolled at about or more than 60% total reduction and annealed. In consequence, the high density was attained. The mechanical properties of these sheets depend more effectively on the elongated grain shape and average grain size than on the scattered fine pores in them.View full abstractDownload PDF (7791K) -
Tadashi Igarashi, Kenya Motoyoshi1976 Volume 23 Issue 3 Pages 104-110
Published: April 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe purpose of this paper is to discuss the hardening mechanisms of Ag-Ni sintered two phase alloys containing fibrous Ni prepared by cold drawing. Deformation behavior during cold drawing and softening behavior during isochronal annealing were studied by hardness measurements.
The results are summerized as follows:
(1) Ag-Ni alloys containing fibrous Ni were obtained by cold drawing of sintered alloys. The hardness of these alloys was higher than that calculated by the mixing rule based on the hardness of Ag and Ni.
(2) In the region of low Ni volume fractions and low reduction, the matrix and secondary phases were deformed with different strain. Deformation in the matrix was larger than that in the secondary phase.
(3) Hardening by fine structure and strain hardening were distingusihed. Structural hardening was represented by the Hall-Petch type relation.
(4) Ag-Ni alloys containing fibrous Ni had a higher recrystallization temperature than that of Ni. The main cause of this behavior was the inhibition of the strain energy relief due to the fine structure.View full abstractDownload PDF (3206K)
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