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Volume 63, Issue 3
Displaying 1-19 of 19 articles from this issue
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Mikito Ueda, Mutsuhito Amemiya, Tatsuo Ishikawa, Toshiaki Ohtsuka1999 Volume 63 Issue 3 Pages 279-283
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSA new process for recovery of aluminum from aluminum dross was developed. The aluminum dross which is obtained as a by-product during casting process of aluminum alloy contains aluminum alloy and oxides of various metals including aluminum oxide. The process consists of two stages: (1) Separation of the aluminum alloy from the oxides by difference in density between the alloy and the oxide in molten salts. (2) Dissolution of oxides into molten salts, and electrolysis of the molten salts to form metallic aluminum from the oxide. This paper is concerned with the first stage for the separation of the aluminum alloy from the oxides by using BaCl2-NaCl-NaF melts. The aluminum alloy completely separates from the oxides in the melts at concentrations of BaCl2 higher than 33.3 mol%, in which the liquid aluminum alloy floats up and the oxides sink down. From a 30 g dross sample, amount of about 24 g of aluminum alloy has been recovered. The remaining oxides contains aluminum oxide, silicon oxide, magnesium oxide and iron oxide. From the aluminum oxide dissolved in the melt, metallic aluminum is formed by electrolysis in a subsequent stage.View full abstractDownload PDF (674K) -
Hirohisa Masuda, Risa Kimura, Naotaka Sakamoto, Kenji Morinaga1999 Volume 63 Issue 3 Pages 284-288
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSBaO-B2O3-ZnO glasses have been studied in order to prepare lead-free glasses with a low-melting point. A glassforming region in the system was determined and thermal expansion coefficients, glass transition temperatures, dilatometric softening temperatures, and densities of the glasses were measured. A glass with a low thermal expansion coefficient comparable to that of PYREX glass was obtained. The behavior of ZnO, an amphoteric oxide, in the glasses was discussed on the basis of viscosities of the melts and chemical shifts of ZnKβ1 in the glasses. In the glass system, the behavior of ZnO depending on the basicity of the glass such as ZnO in silicate glasses was not observed. It was revealed that ZnO in the glass system tended to become the four-fold coordination and contributed as network former (NWF) to maintain the stability of the network structure in the glasses. The change in the properties of the glasses in the system BaO-B2O3-ZnO was termed “the zinc oxide anomaly” since it was caused by the coordination number change of ZnO as NWF.View full abstractDownload PDF (475K) -
Kiyoshi Shibata, Yoshio Waseda1999 Volume 63 Issue 3 Pages 289-297
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSRecycling of materials is not always economically or environmentally beneficial, especially when the demand for its cascading use is limited by contamination of impurities. The impurity content in metal scrap will increase, when the recycling ratio becomes high. It is anticipated that the removal of such impurity requires additional load, such as energy consumption or environmental burdens, which can eliminate the importance of recycling. In this work, a system model has been developed and the requirement for the performance of the impurity removal process to meet the original purpose of the recycling is discussed. The modeled system consists of three processes; smelting of ore, simple re-melting of scrap and removal of impurities in the scrap. The relationship between the amount of recovered scrap and its impurity content was expressed as a binomial function. Contamination factor was defined as a ratio of standard deviation of the binomial equation to average content of the impurity. The amount of the production in each process was calculated, as a function of the impurity removal efficiency, yield and the contamination factor. The total load of the system and the allowable maximum load in the impurity removal process were described as a function of the recycling ratio and the performance of the impurity removal process. If the impurity removal efficiency or the yield is too low, the allowable maximum load becomes lower. The contamination factor has little effect on the maximum allowable load, but the impurity content itself affects significantly the requirement for the performance of the impurity removal process. The model, proposed in this work, is capable of giving quantitative information necessary for process development and operation control.View full abstractDownload PDF (790K) -
Toshihiro Yano, Xu Ling, Tatsuo Yokote, Ryuuta Onodera1999 Volume 63 Issue 3 Pages 298-304
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to examine the effect of grain boundary sliding on fracture in leaded alpha brass during hot working, hot compression tests with the strain rate of 0.1-0.4 s−1 were carried out at 973 K for Cu-35 mass%Zn including 0-1.5 mass% lead using specimens with three different grain sizes ranging from about 50 to about 200 μm in diameter. In addition, the effectiveness of changing the surface phase for improving poor formability in leaded alpha brass was shown. The results were as follows:
(1) The fracture was influenced by lead content and grain size. In non-leaded alpha brass, fracture did not occur at any grain size. In leaded alpha brass containing 0.5-1.5 mass% lead, the fracture occurred easier with an increase in grain size (>100 μm).
(2) The fracture occureed only at the free surface and was attributed to the grain boundary sliding.
(3) The grain boundary slid more easily as the grain size increased. The amount of sliding was increased by the existence of lead particles. The behavior of grain boundary sliding corresponded to the fracture behavior of leaded alpha brass during hot working.
(4) The poor formability of leaded alpha brass was remarkably improved by changing the phase of the specimen surface from alpha to beta. This result suggests that the alpha grain boundary slides more easily than the beta grain boundary essentially.View full abstractDownload PDF (1674K) -
Masaaki Ishio, Masakazu Umeda, Hirofumi Inoue, Kenji Morii1999 Volume 63 Issue 3 Pages 305-311
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSAs a practical material for use as the anode cases of button-type batteries, we have studied clad metals consisting of Cu/18Cr-8Ni-Fe(SUS304)/Ni, and shown the possibility of improvement in strength and anisotropy by annealing and cold rolling. From the comparison of the clad metals and SUS304 plates about texture or r-values, we have obtained the following results:
(1) The clad metals showed higher strength and formability, by 25% cold rolling after annealing. Tensile strength increased from 657 MPa to 862 MPa, and the Δr-values reduced from 0.25 to 0.08. This is because the texture of the 18Cr-8Ni-Fe core material in clad metal has a rather wide spread in orientation, when compared with that of the SUS304 plates, and the formation of Goss orientation {110}⟨001⟩ during cold rolling, which leads to a remarkable anisotropy, is largely suppressed.
(2) The in-plane anisotropy of r-values was calculated from an orientation distribution function based on the Taylor theory. It agreed well, qualitatively, with that of measured r-values in both of the clad metals and SUS304 plates.
(3) For the clad metals, the core material is deformed without direct contact with the rolls. Therefore, the characteristic texture formation in clad metal may be caused by the suppression of shear deformation.View full abstractDownload PDF (601K) -
Noboru Yoshikawa, Yoshiyuki Watanabe, Zully Matamoros Veloza, Atsushi ...1999 Volume 63 Issue 3 Pages 312-318
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSAl/Al2O3 composite bodies are known to be obtained as reaction products between SiO2 and molten Al. In this study, quartz glass rods of 5 and 15 mm in diameter were dipped into molten Al at various temperatures between 973 and 1573 K in Ar atmosphere or in air. Growth rates of the reaction layers were measured and microstructures of the composite bodies were observed. Following results were obtained:
According to the X-ray diffractometry and the wave dispersive X-ray microanalysis (WDX), the reaction products consisted of Al and Al2O3, and the concentration of Si was less than 5%. Volume fraction ratio of Al and Al2O3 phases in the composite bodies was almost 1:3. It was interpreted that the volume fraction of Al phase resulted from compensation of the molar volumes differences between SiO2 and Al2O3.
In the temperature range between 973 and 1073 K, thickness of the reacted layer increased linearly with the time and the growth rate of the reacted layer (gradient of the time-thickness curve) increased with the temperature. However, in the temperature range between 1073 and 1273 K, the growth rate decreased with the temperature. Al2O3 phase produced by the reaction changed in this temperature range and this phase change is considered to be related to the decrease in growth rates.
The thickness increased parabolically with the time above 1373 K, and the parabolic growth rate increased with the temperature. Coarsening of the composite microstructures occurred in this temperature range, remarkably. Transfer rate of molten Al in the composite body increased due to the increase in the width of Al channels. Therefore, growth rate of the reaction layer increased.View full abstractDownload PDF (977K) -
Nagahiro Saito, Akio Fuwa1999 Volume 63 Issue 3 Pages 319-325
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSFrom our previous experimental study of the Si chemical vapor deposition in Si2Cl6-H2 system, the following elementary reaction mechanism was proposed: decomposition of Si2Cl6 to produce SiCl2, which becomes the adsorbent; Si2Cl6(g)→2SiCl3(g)→SiCl4(g)+SiCl2(g)(→SiCl2(a)), and hydrogen reduction reaction of the absorbed SiCl2 to produce Si(s). The preliminary quantum chemistry study for this reaction mechanism has shown that the reaction is so infeasible that the above-mentioned elementary reaction mechanism is unreasonable. The most feasible and appropriate reaction mechanism has been shown as follows:
(This article is not displayable. Please see full text pdf.)
\ oindentwhere, a is the active site on silicon surface. On the assumption that step 3 is the rate-determining step, this elementary reaction mechanism can explain the experimental observation in the rate expression on the concentration dependence with respect to Si2Cl6 and H2.View full abstractDownload PDF (592K) -
Koji Kakehi1999 Volume 63 Issue 3 Pages 326-332
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe effects of crystallographic orientation on the tensile and creep strength of the notched specimens of single crystals of a nickel-base superalloy have been examined at 900°C. The different plastic anisotropy among four kinds of the notched specimens was interrupted by changing the arrangement of slip systems. The tensile and creep strength of the notched specimens were affected by the crystallographic orientations not only in the tensile direction but also in the thickness direction. At 700°C, assuming that {111}⟨\bar101⟩ type slip systems were operated in the tensile tests and the {111}⟨112⟩ type slip systems in the creep tests, the test results could be explained very well. In this study, at 900°C, the results of the tensile tests and creep tests were discussed on the assumption of that {111}⟨\bar101⟩ type slip (octahedral slip) systems were in operation. The test results could not be explained just by the operation of the {111}⟨\bar101⟩ slip system. Therefore, it was assumed that the operation of {010}⟨101⟩ type slip (cube slip) systems and diffusion-controlled deformation mechanisms should be taken into account at this temperature.View full abstractDownload PDF (582K) -
Satoru Ishihara, Tsuneyuki Tanizawa, Koutarou Akashiro, Norio Furushir ...1999 Volume 63 Issue 3 Pages 333-340
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSGrain boundary sliding during superplastic deformation has been investigated for fine-grained Al2O3-20%ZrO2(3 mol%Y2O3 doped ZrO2) ceramics prepared with no additive in order to estimate the grain boundary sliding contribution to superplastic deformation for ceramic materials. Large strains are obtained by compression tests at the temperature of 1400 and 1500°C. Grain boundary sliding is clearly found to take place during the superplastic deformation. The intragranular strain contribution to the total strain was estimated from the aspect ratio of the grains after deformation. The grain boundary sliding was measured by an imaginary scratch line method and a stereographic analysis method. The grain boundary sliding contribution to the total strain can be estimated from the results of the stereographic analysis method, and multiplication by a calibration factor which compensates for the difference between grain boundary sliding at the surface and at the interior of the specimen. The contribution of the Al2O3-20%ZrO2 ceramics are estimated to be about 40∼60%, which increases gradually with strain rate.View full abstractDownload PDF (873K) -
Tomomi Yamaguchi, Tomohiro Akiyama, Jun-ichiro Yagi1999 Volume 63 Issue 3 Pages 341-344
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSCombustion synthesis of a Cu-ZnO system as a typical catalyst for methanol production has never been reported in the literature inspite of its attractiveness. In this paper, the combustion synthesis of Cu-ZnO(-Al2O3) catalysts for the direct synthesis of methanol from combustion offgas CO-CO2-H2, was studied through differential thermal analysis, X-ray diffraction and MeOH synthesis experiments. The catalyst prepared by the precipitation method, 34.3 mol%Cu-51.4 mol%ZnO-14.3 mol%Al2O3, was most active for dimethyl ether ((CH3)2O, DME). However, the combustion-synthesized catalyst showed only MeOH activity, in which MeOH yield per specific area of the catalyst was the same value as that by the precipitation method. This suggests a possibility of a new catalyst preparation process based on combustion synthesis.View full abstractDownload PDF (294K) -
Katsutoshi Matsumoto, Shoji Taniguchi, Atsushi Kikuchi1999 Volume 63 Issue 3 Pages 345-351
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSLeaching behaviors of synthetic zinc ferrite particles in acid solutions (HNO3, HCl and H2SO4) were studied by the use of an agitated vessel.
The rate-controlling step was found to be the chemical reaction at the surface of the particle. The apparent activation energy was about 66 kJ/mol for HNO3, 92 kJ/mol for HCl, and 68 kJ/mol for H2SO4, respectively.
Only in some cases of leaching with HNO3 solution, did the leaching rate appear to decrease with time. In that case, a nonstoichiometric dissolution with a preferred dissolution of zinc was observed. This phenomenon is more pronounced at high temperatures and high agitation speeds. Scanning Electron Microscope observations showed that the particles agglomerated. Furthermore, the number of particles in the solution decreased during the experiments.
The results of several analyses; XRD, FT-IR spectrum, EDS and EPMA, showed that there were precipitates composed of iron and nitrate between agglomerated particles. These precipitates appear to cause the nonstoichiometric dissolution and the particle agglomeration which decreases the reaction area of the particles.View full abstractDownload PDF (578K) -
Sachiko Hiromoto, Hideo Numata, An Pang Tsai, Kouzou Nakazawa, Takao H ...1999 Volume 63 Issue 3 Pages 352-360
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSRibbons of amorphous alloys, Pd78Si16Cu6−xCrx (x=0, 2, 4 and 6 mol%), were polarized in an artificial body fluid, deaerated PBS(−), as the electrolyte to estimate the performance of the alloys as biomaterials with the intention of developing new high corrosion resistant amorphous alloys. Three kinds of surface conditions of amorphous alloys were prepared: as-received (by single roller melt spinning method), polished and just-polished (within 300 s after polishing). Polished crystalline alloys were also polarized as controls.
Icorr (corrosion current density) and Icrit (critical passive current density) of the as-received amorphous alloys and the polished crystalline alloys decreased with increasing chromium content. Corrosion resistance of these alloys was improved by the addition of chromium. Icorr, Icrit and Ips (passivation current density) of the polished amorphous alloys were lower than those of the polished crystalline alloys and these values of the former alloys were independent of chromium content. This indicates that corrosion resistance of the polished amorphous alloys is higher in the artificial body fluid than that of the polished crystalline alloys.
To determine the cathodic reactant on the as-received amorphous alloys in deaerated PBS(−), one of the alloys was polarized in deaerated 2.5 kmol%H2SO4. The cathodic Tafel slope in PBS(−) was the same as that in H2SO4, indicating that the cathodic reactant in PBS(−) was identified as hydrogen ion. In addition, polarization curves of pure palladium, pure copper and pure chromium were examined to determine the anodic reaction. Ecorr (corrosion potential) of the pure palladium was similar to those of the alloys, suggesting that palladium ion is preferentially released from the alloys under the immersion in deaerated PBS(−).
Icorr, and Icrit of the polished amorphous alloys were lower than those of the as-received amorphous alloys. To discuss the improvement in corrosion resistance by polishing, just-polished alloys were also polarized. The curves of the as-received and the just-polished alloys contained negative loop except the polished alloys. Icorr and Icrit of the just-polished alloys were slightly larger than those of the polished alloys. These results indicate that the surface morphology of the amorphous alloys changed during the exposure to air, causing the increase in corrosion resistance.View full abstractDownload PDF (770K) -
Yukio Inokuti1999 Volume 63 Issue 3 Pages 361-366
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to clarify the influence of iron loss and domain structure of TiN-coated silicon steel sheets with different gauges, TiN coating by the hollow cathode discharge (HCD) method was performed on polished very thin (0.10 mm) and thin (0.20 mm) silicon steel sheets. Domain structures of (011)[100] single crystals of silicon steel, which were chemical polished, TiN-coated and then domain refined by scribing with a knife at 4 mm widths perpendicular to the rolling direction, were observed by electron microscopy.
Very thin 0.10 mm TiN-coated silicon steel showed ultra-low iron loss of W13⁄50=0.12 W/kg after the domain refinement, whereas thin 0.20 mm TiN-coated silicon steel showed W13⁄50=0.26 W/kg.
The domain structures obtained by TiN coating and inducement of a small local strain by scribing produced a drastic domain refinement, and the variation in domain structure was more pronounced with thinner gauges. The variation in iron loss was consistent with the changes in domain structure.
It should be noted that the iron loss of the very thin 0.10 mm TiN-coated silicon steel, which was about 5 times as thick as amorphous FeSiB (0.02 mm thick), showed ultra-low iron loss comparable to that of the much thinner material.View full abstractDownload PDF (1130K) -
Yoshihiro Takahara1999 Volume 63 Issue 3 Pages 367-374
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSWe have investigated the formation and its kinetics of nanocrystalline structure in amorphous Fe74Cu1Nb3.5Si13B8.5 alloy by differential scanning calorimetry, electrical resistivity measurement, X-ray diffraction and transmission electron microscopy.
The solid solution bcc-Fe(Si) phase including Si appeared as the primary crystal during isothermal annealing at 773 K. The maximum grain size of the crystalline phase was about 26 nm after annealing for 360 ks. The volume fraction of the nanocrystalline phase after the annealing was estimated to be about 70% from the analysis of X-ray diffraction profiles. A progressive increase in the Si content of the solid solution bcc-Fe(Si) during crystallization has been revealed. We estimated the diffusivity D from the annealing time dependence of the largest grain size, and obtained D=2.0×10−20 m2/s. This value agrees with the diffusivity for Nb volume diffusion in bcc-Fe at 773 K, which means that Nb diffusion is the rate-determining process for the growth of the bcc-Fe(Si) crystals. On the other hand, the DSC curves measured for the formation of nanocrystalline structure were well reproduced by the grain growth model proposed by Chen and Spaepen.View full abstractDownload PDF (1047K) -
Shinji Fujimoto, Shigeki Kawachi, Toshio Shibata1999 Volume 63 Issue 3 Pages 375-382
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSUltra-violet (uv) light of wavelength 300 nm was irradiated on Fe-18Cr alloy during passivation in a deaerated 0.1 kmol·m−3 H2SO4 solution to modify the property of passive film. XPS analysis of the passive film revealed that uv light irradiation during passivation enhanced Cr enrichment in the oxide layer of the passive film, assuming that passive film consists of three layers; hydrocarbon contaminant covering a hydroxide layer of Cr and an underlying oxide layer of Cr and Fe oxides. The increasing Cr content in the film correlated with an improved pitting corrosion resistance in solution. As usually observed, the Cr content in the passive film increases with passivation time without uv irradiation. The uv irradiation accelerated the Cr enrichment in the passive film to reach a steady Cr content in a shorter time. The steady Cr content, however, was not necessarily increased by uv irradiation. Therefore, uv irradiation enhanced Cr enrichment mainly at the initial stage of passivation. The photoelectrochemical current response test revealed that the semiconductor property of the passive film changes from n to p type with time in the initial stage of passivation. The accelerated Cr enrichment was observed mainly during the period of the n-type semiconductor property in which field-assisted cation outward migration is possible to be accelerated by electric field in the film. The experimental results in the present work suggest that the photo excitation in the passive film by uv irradiation changes the energy band slope to accelerate outward migration of Fe ions resulting in the enrichment of Cr in the film.View full abstractDownload PDF (883K) -
Satoshi Emura, Masuo Hagiwara, Yoshikuni Kawabe1999 Volume 63 Issue 3 Pages 383-390
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSTi3Al-based alloys, especially alloys containing large amounts of Nb to improve their ductility, are attractive materials for aircraft and automobile parts. However, these alloys do not have good high temperature mechanical properties. In the present study, Ti3Al-Nb alloys reinforced by TiB ceramic particulates were produced using blended elemental (BE) powder metallurgy (P/M). To improve their mechanical properties, the modification of the matrix microstructure was attempted by heat treatment.
Titanium powder, Niobium-Aluminum master alloy powder and TiB2 ceramic powder were used as starting powder materials. Blended powders were cold pressed using mechanical pressing, vacuum sintered at 1823 K and finally hot isostatic pressed (HIP’ed) at 1373 K and 200 MPa for 10.8 ks. During sintering, TiB particulates were in-situ formed and dispersed in the matrix homogeneously. The matrix microstructure of the composite produced by this conventional method showed a colony microstructure with diameters ranging from 5 μm to 20 μm. Modification to a uniform, finer colony microstructure with a diameter of 5 μm was achieved by annealing the composite at 1573 K followed by air-cooling. This resulted in improved high cycle fatigue strength with almost no fatigue data scatter.View full abstractDownload PDF (2416K) -
Yukihiro Isoda, Yoshikazu Shinohara, Yoshio Imai, Isao Albart Nishida, ...1999 Volume 63 Issue 3 Pages 391-396
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe phase analysis was carried out for the (1−x)FeSi2+xBSi2 system in the composition range of 0≤x≤0.08 by an X-ray technique. It was found that B atoms in FeSi2 were substituted by Fe atoms and that a solid solution Fe1−xBxSi2 was formed in the composition range of x≤0.03. The thermal shock resistance was estimated by the number of quenching cycle times, before crack was initiated by heating to 1073 K and subsequently water quenching to 300 K. For x=0, a crack was initiated on the specimen surface with one quenching cycle, while no crack was found until forty quenching cycles for x=0.03. The effect of B atoms on thermoelectric properties of the sintered (1−x)FeSi2+xBSi2 have been investigated at 300 K, and the thermoelectromotive force E0 and effective mean resistivity re were observed up to a temperature difference of 800 K. It was found that B atoms acted as the donors. The absolute value of the Seebeck coefficient at 300 K was 103.5 μV K−1 for x=0 and increased up to 681 μV K−1 for x=0.03. Lattice thermal conductivity at 300 K decreased with increasing x and the reduction ratio was 12% for x=0.03. The effective maximum power Pe(=E02⁄4re) of p-type FeSi2 doped with Mn and B was lower than that of Mn doped FeSi2, while Pe of n-type FeSi2 doped with Co and B was equivalent to that of un-doped B. A p-type or n-type thermoelectric material with a high thermal shock resistance was formed by double doping of FeSi2 with Mn and B or with Co and B, respectively.View full abstractDownload PDF (449K) -
Junya Maeda, Yuh Shiohara1999 Volume 63 Issue 3 Pages 397-405
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIt is necessary to understand the solidification behavior because the mechanical properties and the thermal conductivity of the YBCO/Ag superconducting current leads prepared by unidirectional solidification method are influenced by the silver particle dispersion. Solidification behavior in the YBCO/Ag superconductor is discussed with the Y2Ba1Cu1O5-Ba3Cu5Ox-Ag (211-035-Ag) quasi-ternary phase diagrams, which were constructed by the analyzes of the solute compositions in the melt. The obtained phase diagram indicates that the solidification of the YBCO/Ag system proceeds through the monotecto-peritectic reaction, expressed as 211+BaO-CuO-rich melt (L1)→Y1Ba2Cu3Oy(123)+Liquid metallic silver (L2). The diffusion fields in the YBCO/Ag system were discussed with using this phase diagram.View full abstractDownload PDF (1030K) -
Tomohiro Uno, Kohei Tatsumi1999 Volume 63 Issue 3 Pages 406-415
Published: 1999
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to clarify the reliability on the mechanical and electrical properties of the bond between Au wire and Al thin pad, corrosion behavior of Au-Al intermetallic formed at the bond interface in the molding resin were investigated. The bonds were annealed at several elevated temperatures, T (423-573 K). Typical degradation was recognized by a decrease in bond strength as well as a remarkable increase in electrical resistance. The molding resin has great influence on the corrosion. Bi-phenyl (BP) epoxy resin was found to cause the degradation approximately six times faster than o-cresole novolac (OCN) epoxy. Activation energies of the bond failure were 1.5 eV (T>450 K) and 2.0 eV (T<450 K) in BP resin and 2.3 eV in OCN resin.
The corroded part was revealed to be Au4Al intermetallic phase formed in the bond interface. The growth rate of corroded layer was proportional to annealing time t, which indicated the corrosion behavior was not diffusion-controlled. Activation energies of the growth rate of corroded layer in the BP and the OCN resin were 1.6 eV, 2.3 eV, respectively, which were very similar to those of the bond failure.
The corrosion reaction of Au4Al and bromide produced minute Au precipitation (fcc) and Al oxide formation. The Al oxide was identified to be amorphous by EDS and electron diffraction.View full abstractDownload PDF (1374K)
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