Corrosion characteristics of the open surface of a Ti-Pd(0.14) alloy have been studied in NaCl-HCl solutions of various concentrations. It has been confirmed that the Ti-Pd alloy shows markedly lower corrosion rates and improved corrosion resistance in comparison with pure titanium in these environments. The electrochemical behavior of the Ti-Pd alloy in these solutions suggests that palladium accumulates on the surface of the Ti-Pd alloy during the initial period of corrosion, the accumulation of palladium on the alloy surface being confirmed by GDS analysis. The corrosion protection is explained by the fact that a palladium enrichment on the surface accelerates the cathodic reaction due to lowering the hydrogen overvoltage, and consequently, shifts the corrosion potential of the alloy into the passive region of titanium. Therefore, the corrosion potential of the alloy is more noble than the critical potential for passivity of titanium.

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The stress corrosion cracking (SCC) resistance of hot-extruded P/M Al–Zn–Mg alloys, Mesoalite, was investigated as compared with that of I/M Al–Zn–Mg alloys and the correlation between stress corrosion resistance and microstracture was studied. SCC resistance about P/M alloys was high as compared with that of I/M alloys and when the solute concentration increased, reduction of SCC resistance about P/M alloys was not observed. The difference in width of PFZ, distribution of precipitates on grain boundary, the amount of metastable phase precipitated in the matrix, tilt angle of grain boundary, grain size and shape was investigated as a cause of the difference of SCC resistance. The large change in the size and shape of grain among these factors was observed. In the P/M alloys, the fiber-like grain elongated to the extruded direction was observed to the equi-axial grain having been observed in the I/M alloys. When stress was applied parallel to elongated grains, the stress perpendicular to the grain boundary was low. Since the SCC resistance is improved when the applied stress perpendicular to the grain boundary is small, it is concluded that the SCC resistance of the P/M alloys which has the fiber-like grain elongated to the ED became large.

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After 2016 Kumamoto Earthquake, we investigated 80 two-storied damaged houses of light-gauge steel structure by microtremor measurement and visual check. We analyzed the relationship of natural frequency of the houses by microtremor measurement and average displacement response spectrum (0.2 - 0.3 seconds) of construction area. As a result, natural frequency of the houses decrease as the displacement response spectrum increase.

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実機評価に頼らぬガスケット開発を行うため，より精度よくシール性能を予測する解析技術が必要．従来のシール性解析は，実機評価で発生するガスケットの経年劣化が未考慮．今回，劣化項目としてコーティングゴムの膜厚低下に着目．単体評価で計測した結果を解析条件として活用し，解析結果を実機評価結果に近づける．

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The microstructure and corrosion resistance of Ti-Pt alloys prepared from Ti and Pt powders by the Spark Plasma Sintering (SPS) method was investigated. The microstructure of SPS’s specimens were observed by scanning electron micrographs and X-ray diffraction patterns. Pt phases were dispersed in the Ti matrix, and a few intermetallic compounds of Ti-Pt were formed around the Pt phases. The corrosion behavior of SPS’s specimens were evaluated by potentiostatic polarization measurement in a 5 mass%HCl solution. The Pt and Ti₃Pt phases may be responsible for high corrosion resistance, and the cathode reaction on Pt phases keeps passive state Ti. Therefore, the Ti matrix becomes appreciably more passive compared with the arc melted Ti-Pt alloys. In this method, the corrosion resistance was improved by adding only a few mass% of Pt.

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The present study was conducted in order to analyze the effects of sintering temperature on the microstructure and corrosion resistance of Ti-M (M=Ru, Rh, Pd, Ir, Pt) alloys prepared from titanium and M powders using spark plasma sintering (SPS). In addition, the practicality of the Ti-Ru alloy as a low-cost Ti alloy was discussed. The specimens were prepared at SPS temperatures of 800, 1100 and 1500°C. The microstructure of specimens were investigated using scanning electron microscopy (SEM) and X-ray diffraction. The corrosion resistances of specimens were determined by potentiodynamic polarization measurement at a scanning speed of 0.124 V/min using a 5% HCl solution open to air at 25°C. Measurement was performed at a specimen potential of from −1.0 to 2.0 V and the potential approached noble.
At a low SPS temperature, SPS alloys show a particle dispersion microstructure, in which the added element phases and intermetallic compound phases are dispersed in the Ti matrix. These phases affect the corrosion resistance of the alloys. At a high SPS temperature, the added elements and compounds are diffused in the Ti matrix, causing the alloy to approach a solid solution microstructure and increasing the formation of metastable βTi. In particular, at a high SPS temperature, in the Ti-Pt alloy increases slightly the amount of βTi, whereas increases greatly the amount of Ti₃Pt. High SPS temperatures reduce the added element phases that serve as the cathodic pole, thus diminishing the cathodic current. In the anodic area, the reduction or dispersion of compound phases reduces the compound active region, thus diminishing the anode current.
Furthermore, high SPS temperatures produce similar polarization curves among Ti-M alloys, and provide SPS alloys having the same corrosion resistance equivalent to that of arc-melted alloys. Therefore, no problem is associated with the replacement of Pd with Ru.

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With a view to developing the high-strength Al-Zn-Mg alloy for weld structure, the weld cracking sensitivity and the stress corrosion susceptibility has been investigated using the samples containing 1-2%Mg, 4-7%Zn, 0.1-0.6%Cu and 0.2-0.6%Ag. The additional elements of Mn, Cr and Zr were slightly added, and the weld cracking sensitivity was investigated to study the improvement of weldability. The results revealed that each element improved the weld cracking sensitivity, and particularly the improved effect proved to be remarkable with the addition of Zr. The reason is considered to be the grain size at the weld metal becoming finer due to the addition of Zr, causing the tensile stress exerted on the grain boundary at the time of solidification shrinkage to be dispersed and reduced. Various welded joints were produced by using the samples containing the chemical composition of final selection, and were subjected to the investigation of mechanical properties. The results have revealed that compared with the conventional weld metal of JIS7NO1, the proof stress of the newly developed alloy was found to be approximately 40% higher in the base metal, and approximately 30% higher in the weld metal.

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With a view to developing the high-strength Al-Zn-Mg alloy for weld structure, the mechanical properties and stress-corrosion cracking sensitivities have been investigated using the samples containing 1-2%Mg and 4-7%Zn, and under the different conditions of heat treatment. At the same time, the sample with 1.75%Mg and 6.0%Zn was selected as an alloy excelling in the aforesaid both properties. Next, 0.1-0.6%Cu and 0.2-0.6%Ag were added to improve the stress corrosion cracking sensitivity, then the stress corrosion cracking sensitivity was investigated. The authous have confirmed that the addition of Cu and Ag remarkably improves the stress corrosion cracking life, which can be explained by anodic dissolution of the grain boundary precipitates to be restrained, due to the reduction of the potential difference with the matrix.

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Tensile properties and stress corrosion cracking (SCC) resistance of Al-8wt.% Zn-1wt.% Mg system alloys with various Cu and La contents were investigated. The influences of additional elements on mechanical properties and SCC life were discussed on the basis of experimental results. The results obtained in the present work are as follows;
(1) Additions of elements of Cu and La were effective to decrease the grain size of those materials. In particular, the grain sizes in alloys containing La contents of more than 1.7wt.% were small at 20μm, comparing with that in the master alloy.
(2) For the present alloys containing La, the second phase particles, consisting of Zn and La, have the capacity of hydrogen storage. These particles were between 5 and 10μm in size, and were dispersed in the matrix homogeneously.
(3) Tensile properties were improved with increasing Cu or La content. For the alloys with Cu and La, the tensile strength was from 450 to 500MPa, and the elongation between 14 and 17%.
(4) The alloys containing La had high resistance to SCC. Their SCC lives were about 15 times as long as that of the master alloy. In conclusion, the alloys added Cu more than 0.6wt.% and La 4.0wt.% were much superior to the master alloy in both the tensile properties and the SCC resistance.

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The present study was conducted in order to analyze the microstructure and corrosion resistance of Ti-M (M=Ru, Rh, Pd, Ir, Pt) alloy prepared from titanium and M powders using spark plasma sintering (SPS). The microstructure of SPS’s specimens were observed by scanning electron microscope and X-ray diffraction. Corrosion resistance was determined by measuring the potentiodynamic polarization at a scanning speed of 0.124 V/min using a 5 mass%HCl solution open to air at 25°C. For this measurement, each specimen was scanned beginning at a potential of −1.0 to +2.0 V (SCE), and potential approached noble.
The microstructure observed that the SPS alloys were the particle dispersion type, with added element phases dispersed in the Ti matrix.
Most of the added elements (Ru, Rh, Pd, Pt) formed Ti-M intermetallic compounds on the border between the Ti matrix and added element phase.
Low dispersion of the added element phase reduces the current density in the cathodic area of the SPS alloy polarization curves, and the current density may also decrease if several compounds are generated. Compared to other Ti-M alloys, the current density of Ti-Ir is low because the dispersion is low and that of Ti-Pt is low because several compounds are generated.
Since the active area of the Ti-M (Ru, Rh, Pd, Pt) compound phase is 0 to 1 V (SCE), the compounds increase the current density in the anode area. In the Ti-Pd and Ti-Pt alloys, corrosion marks were observed where the TiPd and TiPt phases were eluded. The Ti-Ir alloy generates no compounds and its current density in the anode area is smaller than those of other Ti-M alloys.
Consideration about Ti-M alloys prepared using SPS is that added element phases are dispersed in the Ti matrix as smaller particles and, moreover, no Ti-M compounds are generated. If Ti-M intermetallic compounds are generated, raising the SPS temperature disperses the compounds into the Ti matrix and reduces the related active area, reducing the corrosion resistance.

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The effect of alloying elements, Fe, Co, Ni, Cr, Mn, Sn, Al, Nb, Ta, V, and Zr, at additions of 1, 3, and 5wt%, has been determined on the corrosion of Ti-Mo alloys by the steeping test, measurement of anodic polarization characteristics, and observation of the test piece surfaces after the steeping test. Addition of Nb, Ta, V, or Zr to the Ti-15Mo base alloy produced the alloys highly resistant to boiling HCl. Preferential attack at the grain boundaries was not observed with the Ti-15Mo-5Nb alloy; the type of corrosion was general corrosion. Corrosion resistance of Ti-15 Mo binary alloys, however, was found to be lower than that of the Ti-15 Mo binary alloys. Polarization curves for the highly corrosion resistant Ti-15 Mo base ternary alloys, containing Zr, Nb, V, or Ta as an alloying element, indicate that the passivation potential decreases in the order of Zr, Nb, Ta, and V. The maximum potential value was obtained at an addition of 1wt% of each alloying element. The secondary passivation range was observed in the polarization curves for all alloys tested, but the effect of the alloying elements was not recognized.

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ベンゼソを種々の過酸化ペルフルオロアルカノイル (C_nF_2n+1(CO) OO(CO)C_nF_2n+1;n=1, 3, 4, 6, 8) でフルオロアルキル化し, さらにスルホン化してフルオロアルキルベンゼンスルホン酸ナトリウム塩 (C_nF_2n+1C₆H₄SO₃Na;Jn=4, 6, 8) を台成した。合成したアルキルベンゼンスルホン酸ナトリウム塩は優れた表面張力低下能を示し, フルオロアルキル鎖長の増加に伴い到達最低表面張力値は低下した (60℃で, n=4の場台, 32.8 (mN/m);n=6の場合, 19.5 (mN/m);n=8の場合, 15.5 (mN/m)) 。また, ミセル内部の微視的極性はフルオロアルキル鎖長の増加に伴い低下した。さらに, フルオロアルキルベンゼンスルホン酸ナトリウム塩の濃厚水溶液において, 液晶 (ラメラ相) が生成した。

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