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Volume 49, Issue 1
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RESEARCH REPORT
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Han Ming CHOW, Ching Tang YANG, Biing Hwa YAN, Fuang Yuan HUANG1999 Volume 49 Issue 1 Pages 2-7
Published: 1999
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSThis paper deals with the fabrication of micro electrode of carbide and micro hole machining characteristics of Ti–6Al–4V alloy. The experimental results show that the material removal rate of carbide machined with small discharge energy in positive polarity is larger than that in negative polarity. And when machining carbide with small discharge energy, the energy supply mode, such as large current and short pulse duration, is efficient for promoting the material removal rate. When machining micro hole of Ti–6Al–4V alloy in positive polarity, compared with negative polarity, both the material removal rate and electrode wear rate are larger. It is also shown that the energy supply mode, such as small current and short pulse duration, can increase the material removal rate because of the formation of smaller debris result in easy ejection of debris out of the small gap. Experimental result indicate that when machining micro hole of Ti–6Al–4V alloy, the most significant effect on micro hole accuracy is the machining depth. The reason is that micro deep hole machining will make debris accumulating on the bottom of micro hole to lead to the occurrence of discharge concentration, and then result in the formation of ellipse hole.View full abstractDownload PDF (1473K) -
Yoshihiro TADA, Susumu HARADA, Isao TSUTSUI, Tsutomu MORIMOTO1999 Volume 49 Issue 1 Pages 8-13
Published: 1999
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSA reduced-current resistance spot welding technique, which utilizes the heat of reaction from reactive inserts together with the Joule heat, has been applied to join aluminum alloy A5052–H34 sheets to pure copper C1100–O sheets. Employing elemental powder mixtures of Ti–Al and Ti–Mn binary systems as the reactive inserts, well balanced tensile shear load and bonded area are obtained by the latter insert especially in a composition of Ti–75Mn. Since expulsion causes damage to the joint strength strongly, welding conditions are investigated to prevent the strength decrease. Application of a F-type electrode in the aluminum side is effective to avoid the surface expulsion by chilling the melted zone formed through the thickness of the aluminum alloy sheets during welding. As the mating electrode in the copper side, a CF-type one with a tip diameter just larger than that of the melted zone is effective to prevent the inter-layer expulsion by its forging effect. When a welding current of 12 kA is applied for 0.2 s with Ti–75Mn insert and welding force of 1 kN to join aluminum alloy sheets of 1 mm and 2 mm in thickness to copper sheet of 1 mm in thickness, tensile shear loads over 1.5 kN and 1.9 kN are achieved by the use of an electrode pair of CFφ6(Cu)/F(Al), respectively.View full abstractDownload PDF (1118K) -
Satoshi HANAWA, Takeshi MIYAZAKI, Makoto SUGAMATA, Junichi KANEKO1999 Volume 49 Issue 1 Pages 14-18
Published: 1999
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSMg–Ce alloys with or without additions of Zn and Ca were rapidly solidified and subsequently consolidated to P/M materials by hot extrusion. Metallographic structures and constituent phases of the rapidly solidified flakes and the P/M materials were studied by TEM and XRD. Mechanical properties were examined for the P/M materials at room and elevated temperatures. The solute Ce content was estimated to 5.6 mass% in rapidly solidified Mg–10 mass%Ce binary alloys, which is about 10 times of the maximum solubility limit. For all the alloys, dendritic cell structures consisting of α–Mg and eutectic cell walls were observed in the rapidly solidified flakes, and fine and uniform dispersion of intermetallic compounds was obtained after consolidation. All the P/M materials showed remarkably high specific strength. The highest tensile strength above 550 MPa at room temperature and 350 MPa at 473 K was obtained in the P/M material of Mg–1O mass%Ce–5 mass%Zn alloy.View full abstractDownload PDF (1096K) -
Ichinori SHIGEMATSU, Naobumi SAITO, Mamoru MABUCHI, Masaru NAKANISHI, ...1999 Volume 49 Issue 1 Pages 19-23
Published: 1999
Released on J-STAGE: June 01, 2007
JOURNAL FREE ACCESSIn order to improve a surface hardness of commercially pure titanium, surface alloying with laser was carried out. Pure silicon, nickel, aluminum powder and a mixture of silicon and 9 mass%WSi2 powder were used for surface alloying. These powders were spread on surfaces of titanium plates and reacted with titanium by CO2 laser beam. Laser irradiation was carried out in argon atmosphere. As a result, when the silicon powder was used, a hard silicide layer (a principal ingredient was Ti5Si3) was formed over thickness 600 μm. In the case of the nickel powder, an alloying layer was consisted of TiNi and Ti2Ni, and its highest hardness was HV600. When the aluminum powder was used, needle-like shapes of precipitates of TiAl3 were observed in aluminum-rich matrix phase. Moreover, in alloying with the powder mixture of silicon and WSi2 powder, concentration phase of tungsten that had over HV1500 hardness were observed locally.View full abstractDownload PDF (1667K) -
Shigenori HORI, Shigeru OKA, Norio FURUSHIRO1999 Volume 49 Issue 1 Pages 24-29
Published: 1999
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSThe discontinuous precipitation process of Mg–Al alloys during aging has been investigated by metallographic observation. In Mg–Al alloys, the initial stage of discontinuous precipitation cell formation had preferential precipitation and local instability of the grain boundary. With continued aging, the local migration of the original grain boundary rose into the adjacent grain. Consequently a solute depleted region was formed behind the advancing grain boundary. After a while, the preproposed S-mechanism required for the formation of double seam morphology appeared. The occurrence of both single seam and double seam morphologies were conformed at both aging temperatures lower and higher than Tm/2 (Tm: melting temperature). These facts do not coincide with Baumann's assumption that the highest dependence is on aging temperature. After the solution treatment, a Mg–9.5Al specimen was cold compressed by 3.2∼15.3%. The cold work prior to aging does introduce additional nucleation sites for general precipitation, with the age hardening somewhat accelerated. The fractional area of discontinuous precipitation cells was suppressed by the deformation twins, only onset of cell formation increased the rate.View full abstractDownload PDF (1614K) -
Kimiyoshi KITAZAWA, Naomi KOBAYASHI1999 Volume 49 Issue 1 Pages 30-34
Published: 1999
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSAlthough the process of CNC incremental forming has the advantage of adaptability to small-lot production of thin shell parts, its production rate is relatively low because numerous tool-paths are generally necessary for producing the required profile. The possibility of a single tool-path process, in which a shell is formed from a flat blank by means of stretching on only one stroke of the tool, has been found for deep conical shells, but has not been illuminated previously for shallow conical shells. Here we report the deformation behavior of shallow conical stretching by the single tool-path process. Aluminum and its alloy sheets were stretched to shallow conical shells with several values of half-apex angle α ranging from 60° to 90°, and the deformation behavior was examined. It was found that, when α was larger than about 80°, the depression occurred at the apex in the shallow conical shell; otherwise the shallow conical shells with sharp-pointed apex was formed. The experimental results can be explained on the basis of the mechanism resulting from metal-flow balance between thinning due to stretching and thickening due to ironing-induced excess metal as α approaches 90° the thickening become predominant, so that the piled-up excess metal forms the depression at apex in the shallow conical shell.View full abstractDownload PDF (1320K) -
Yasuyoshi FUKUI, Hiroshi OKADA, Noriyoshi KUMAZAWA, Yoshimi WATANABE, ...1999 Volume 49 Issue 1 Pages 35-40
Published: 1999
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSThe centrifugal method is one of the functionally graded material (FGM) manufacturing methods proposed by the authors. However, there are certain difficulties in applying the centrifugal method to an alloy melt with high viscosity and low heat capacity. The centrifugal casting system under a vacuum condition is, thus, adopted and designed to improve the former system in air. A new system is satisfactorily constructed and Al–Al3Fe FGM of a thick-walled tube is manufactured from Al–10 mass% Fe master alloy. The particles of intermetallics are confirmed to the Al3Fe intermetallic by EDX analysis. The graded composition of Al3Fe in aluminum matrix is examined and is varied from pure aluminum at inner surface of the tube to 40 vol% Al3Fe at outer plane of the tube. The corresponding graded Young's modulus and thermal expansion coefficient of Al–Al3Fe FGM vary from 71 to 99.5 GPa and from 25.5 × 10−6 to 21.3 × 10−6 K−1, respectively. Tensile tests are carried out using thin plate standard specimen for which Al3Fe grains are homogeneously distributed statistically. The averaged volume fraction of Al3Fe in the specimens, which are tested, is about 28 vol%. Tensile strength of 94 MPa at 0.49% tensile strain and Young's modulus of 90 GPa are obtained.View full abstractDownload PDF (1352K)
REVIEW
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Masashi YAMAMOTO1999 Volume 49 Issue 1 Pages 41-44
Published: 1999
Released on J-STAGE: June 01, 2007
JOURNAL FREE ACCESSDownload PDF (877K)
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