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Volume 67, Issue 5
Displaying 1-7 of 7 articles from this issue
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Keiichiro Oishi, Shinji Tanaka, Yoshiyuki Goto2003 Volume 67 Issue 5 Pages 219-225
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSWe have developed a free-cutting copper alloy “75.5Cu-3Si-0.1P-Zn” free of lead which is known to be harmful to the human body. The microstructure of this developed alloy consists of α, κ and γ phases. The two hard κ and γ phases act as a source of stress at the time of cutting. As a result, the 75.5Cu-3Si-0.1P-Zn alloy is obtained in finely segmented chips with low cutting resistance. Incidentally, for plumbing fixtures such as cocks, vessels, valves, and joints related to the daily intake of tap water, copper alloys containing 2∼6 mass% lead are used. A switch to a lead-free material in the water supply system is urgently required. At the same time, accidents due to dezincification corrosion associated with water quality are frequently encountered in Japan, and there is a strong demand for materials with excellent dezincification corrosion resistance. In this study, we investigated the microstructure and dezincification corrosion resistance of the developed alloy by the ISO 6509 test method.
Single-phase alloys of α, κ and γ phases were prepared by laboratory methods and their dezincification corrosion was evaluated. The α phase and κ phase each has excellent dezincification corrosion resistance and the γ phase also has good dezincification corrosion resistance. Therefore, the developed alloy consisting of these phases is believed to have excellent dezincification corrosion resistance.View full abstractDownload PDF (2111K) -
Masahiro Kitada, Fumiyoshi Kirino, Tooru Tsuru, Katsuhisa Sugimoto2003 Volume 67 Issue 5 Pages 226-231
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe electrochemical characteristics and corrosion behavior of the Niiro-colored Cu-1 mass%Au alloy have been investigated. The oxidation potential of the Niiro-colored Cu-1 mass%Au alloy is higher than that of a raw Cu-1 mass%Au alloy. The reaction electron number of the Cu-1 mass%Au alloy and the Niiro-colored Cu-1 mass%Au alloy is approximately 1 in 5∼14 pH solutions. The electron number of the Niiro-colored Cu-1 mass%Au alloy is similar to that of Niiro-colored Cu. The Niiro-colored Cu-1 mass%Au alloy surface consists of two layers chemically. The thin upper-layer is a copper (II) oxide such as CuO and the underlayer is a copper (I) oxide such as Cu2O. This structure is the same as that of Niiro-colored Cu. The Niiro-colored Cu-1 mass%Au alloy shows good corrosion resistance when the specimens are exposed at 353 K in 90%RH atmosphere. The corrosion current of the raw Cu-1 mass%Au alloy in a solution containing Cl− of 8.3 pH is higher than that of the Niiro-colored Cu-1 mass%Au alloy. These results indicate that the corrosion resistance of the Niiro-colored Cu-1 mass%Au alloy is higher than that of the raw Cu-1 mass%Au alloy without Cl−. A copper oxide layer formed on the surface of the Cu-1 mass%Au alloy protects the alloy from corrosion.View full abstractDownload PDF (380K) -
Takashi Sugizaki, Hidehiro Nakao, Takashi Kimura, Tohru Watanabe2003 Volume 67 Issue 5 Pages 232-238
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe BGA joint properties including the joint strength and the interfacial structure have been investigated in detail between the lead-free solders containing Sn-8.8Zn and Sn-8.0Zn-3.0Bi with low melting temperature and the replacement gold plated film on the electroless nickel-phosphorus deposits. The results indicate that both Sn-8.8Zn and Sn-8.0Zn-3.0Bi solders can be readily jointed with the substrate in the same way as the conventional Sn-37Pb solder at the peak temperature of 230°C. The joint strength of Sn-8.8Zn solder is higher than that of Sn-8.0Zn-3.0Bi solder, and both of them are higher than that of Sn-37Pb under same surface finishing. Moreover, γ2(AuZn3) intermetallic compound occurs as the reaction layer at Sn-8.8Zn and Sn-8.0Zn-3.0Bi joints, and the bismuth crystals occur at Sn-8.0Zn-3.0Bi joint. The hot bump pull testing results clearly show that the fracture of solder ball occurs along the reaction layer of γ2(AuZn3) intermetallic compound since this reaction layer or bismuth crystals in the joint causes the decrease of jointing strength.View full abstractDownload PDF (1881K) -
Zhan Zhou, Hidenori Shirasawa, Akira Ohmori2003 Volume 67 Issue 5 Pages 239-246
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe microstructural change of YSZ plasma sprayed coating in penetration of manganese liquid metal, under a vacuum atmosphere, was investigated and the densification mechanism was studied. During the process of penetration, it was found that the liquid Mn rapidly penetrated into the internal connected porosities of the coating, and dense coating was formed by liquid sintering of the stuffed Mn. With this treatment, the volume of YSZ solid phase increased to 99.3% from 85.0% of as sprayed coating. By analyses of the microstructure and mechanism of densification, the following three steps were found to be involved: \ding172 quick densification associated with forming of partial dense areas, \ding173 spheroidizing of particles by shape accommodation, and \ding174 coalescence of particles. Additionally, the diffusion of Mn from liquid Mn to YSZ particles and the solution of YSZ particles to liquid Mn were also involved. The quick densification of the coating during the early step of penetration was mainly due to the great capillary attractive force generated in filling of liquid Mn in fine porosities among lamellae particles which are characteristic with sprayed coating. The sintering densification in the middle and latter steps was considered to be achieved by solution-reprecipitation of YSZ solid phase in liquid Mn.View full abstractDownload PDF (989K) -
Shinji Ando, Kouichi Saruwatari, Takayuki Hori, Hideki Tonda2003 Volume 67 Issue 5 Pages 247-251
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe fatigue crack growth behavior of magnesium single crystal was investigated in order to clarify the orientation dependence of fatigue crack propagation mechanisms. Four types of compact specimens with respect to active slip and twin systems at a crack tip were prepared from magnesium single crystals grown by the Bridgman technique. In the case of the plane and the direction of notch are (1\bar210) and [10\bar10] respectively, fatigue crack propagated parallel with the notch, while the fatigue crack propagated inclined 30 degrees from the initial notch in the case of (10\bar10)[1\bar210] notch. In both cases, the growth directions of their cracks were [10\bar10] and the configurations of their crack surfaces were similar. From TEM observation, it was found that pyramidal slip systems with (c+a) Burgers vector were activated at the crack tip. From these results, a fatigue crack propagation mechanism was proposed. In the case of (1\bar210)[0001] notch, fatigue crack propagated to [0001] at low stress intensity factor range, ΔK and the growth direction was deflected in parallel to basal plane at high ΔK. In the case of (0001)[1\bar210] notch, fatigue crack propagated along the basal plane being accompanied by {10\bar12} twins. The fatigue crack growth rate of the specimen with (10\bar10)[1\bar210] notch was the lowest in the four type specimens. It is concluded that the fatigue crack propagation behavior of magnesium changes greatly with crystallographic geometry of notch.View full abstractDownload PDF (1149K) -
Yubo Wang, Kazuhiro Matsugi, Osamu Yanagisawa2003 Volume 67 Issue 5 Pages 252-258
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSBased on the constitutive equation for cold isostatic compaction of metal powder, which was previously reported by us, the constitutive equation for general stress states has been proposed as follows,
(This article is not displayable. Please see full text pdf.)
\ oindentJ2′ and J1 are the second deviatoric stress invariant and the first stress invariant respectively and σeq is equivalent stress.
This equation was applied to estimate pressure transmission transfer coefficient, the relation between uniaxial pressure and relative density for pure aluminum and 7075 aluminum alloy powder in closed die compaction, and rolling load in cold powder rolling for pure aluminum powder. From the comparison of their calculated results with the experimental ones, it was shown that the proposed constitutive equation is correct.View full abstractDownload PDF (919K) -
Yosuke Tazaki, Hiromitsu Ino, Katsuro Oda2003 Volume 67 Issue 5 Pages 259-262
Published: 2003
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to determine the Zr occupation position in Nd2Fe14B, we prepared melt-quenched ribbons of Nd11.77−xFe82.35B5.88Zrx and Nd11.77Fe82.35−xB5.88Zrx(x=0, 1, 2, 3, 4) alloys, in which Zr atoms replace for Nd and Fe of the stoichiometric alloy composition, respectively. The result of X-ray diffraction shows that the Nd2Fe14B phase shift to higher angles with increasing substitution of Zr in both kinds of alloys. The lattice parameters a and c were determined by using Cohen’s method. Since the atomic radius of Zr atom is smaller than that of Nd atom, and larger than Fe atom, it is concluded Zr atoms substitute Nd sites of Nd2Fe14B, irrespective of alloy composition. Besides it is found the decrease in Curie temperature of the (Nd, Zr)2Fe14B is parallel to that in the lattice parameters.View full abstractDownload PDF (309K)
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