Nb, Ta, and Zr are the favorable nontoxic and allergy-free alloying elements suitable for use in titanium alloys for biomedical applications. Low-rigidity titanium alloys composed of nontoxic and allergy-free elements are receiving considerable attention. The advantage of low-rigidity titanium alloys in the healing of bone fracture and bone remodeling is successfully proven by using tibia of rabbit as a fracture model. Ni-free superelastic and shape memory titanium alloys for biomedical applications are being actively developed. The mechanical properties such as fatigue and fretting fatigue are important from the viewpoint of mechanical properties, which may be collectively referred to as mechanical biocompatibilities in the broad sense, in addition to the rigidity, i.e. Young’s modulus. Bioactive surface modifications of titanium alloys for biomedical applications are very important for achieving further biocompatibility.

Friction stir welding (FSW) is a welding process which deals with joining parts in a solid state at low temperature to result in welded parts with excellent mechanical performance, such as low distortion and high tensile strength. Additionally friction stir welding is applicable to aluminum alloy products with precision dimensions. By using friction stir welding parameters, this research studies the tensile strength, hardness, elongation rates, and shrinkage of extruded 6061-T6 alloy. Results indicate that the joining strength of the extruded 6061-T6 alloy can reach 78% of the base metal after friction stir welding. Meanwhile, welding parameters can accurately predict and control the welding distortion of welded products. This research applies these results in the manufacturing of launch boxes to arrive at a technology that can be directly applied to welded products without expensive as-welded modifications.

A new Mg-Gd-Zn-base cast alloy was developed for high strength casting products. Effects of Zn content on microstructures and tensile strength were investigated. Both Mg-3.2%Gd-0.5%Zn-0.2%Zr (in mol%, 0.5GZ) and Mg-3.2%Gd-0.75%Zn-0.2%Zr (0.75GZ) alloys showed remarkable age hardening by precipitation of β′ phase with bco structure as similar to Mg-Gd-Y-Zr alloy. The precipitates are finer and denser than those of Mg-Gd-Y-Zn-Zr alloy by Zn and a large amount of Gd addition. Mg₃Gd compound particles remained at grain boundaries after solution treatment. Long period stacking ordered (LPSO) phase did not form. It is considered that Mg₃Gd particles suppressed grain coarsening during the heat treatment, and provided fine grain structure of about 30 μm in diameter. Tensile strength of the T6-treated 0.5GZ alloy was 410 MPa at room temperature and the high strength was kept by 473 K.

The notched tensile strength (NTS) of Ti-4.5Al-3V-2Fe-2Mo specimens with distinct heat treatment conditions was investigated and correlated to microstructures. The specimens were solution-treated at either 980 or 870°C (above or below the β-transus) and then water-quenched prior to aging treatments. After aging at 482, 593, and 704°C, titanium martensite (α′ or α″) decomposed into α and β with distinct sizes. Additionally, the specimens aged at 482°C were particularly susceptible to notch brittleness, regardless of the solution temperature. As the aging temperature increased, the lower hardness associated with coarsened α+β structures resulted in decreased notch brittleness of the alloy. In general, the specimens containing primary α in microstructure were prone to brittle fracture and reduced NTS. The alignment of martensite packets (or needles) with respect to the crack growth direction could affect the fracture appearance of the specimens, particularly for the coarse-grained specimens which were solution-treated at 980°C. Furthermore, the existence of grain boundary α for the specimens aged at 593°C or higher promoted grain boundary sliding during notched tensile tests.

The microstructural mechanisms during dynamic globularization were investigated for ELI grade Ti-6Al-4V alloy with initial martensite microstructure. For this purpose, compression tests were carried out isothermally at 1073 K up to the strains of 1.0 and 1.4 with the strain rates ranging from 10⁻³ s⁻¹ to 1 s⁻¹. Fully dynamically globularized specimen exhibited higher Vickers hardness values due to the finer grain size and higher dislocation density compared to the conventionally produced one, i.e., partial dynamic globularization by subsequent annealing. The strain rate sensitivity (m) values of the flow stresses at initial stage (ε≈0.05) and final stage (ε≈1.4) of deformation were ≈0.15 and ≈0.36, respectively, leading to the conclusion that deformation was controlled by dislocation glide/climb at low strains and grain boundary sliding at high strains. Also, microstructural evolution during dynamic globularization was rationalized by examining the microstructures associated with kinking and fragmentation of lamellar plates.

The alloying effects of Ru and W on the hydrogen solubility, the resistance to hydrogen embrittlement and hydrogen permeability are investigated quantitatively for Nb-based hydrogen permeable alloys. It is found that the hydrogen solubility decreases by the addition of alloying element into niobium or by increasing the temperature. As a result, the resistance to hydrogen embrittlement is improved by reducing the hydrogen concentration. On the other hand, the hydrogen flux, J, through the alloy membrane increases linearly with increasing difference of hydrogen concentration, ΔC, between both sides of the membrane. It is shown that the Nb-5 mol%X (X = Ru and W) alloys possess excellent hydrogen permeability without showing any hydrogen embrittlement when used under appropriate permeation conditions, i.e. temperature and hydrogen pressures. Also, the hydrogen diffusion coefficients during the practical hydrogen permeation at high temperature are evaluated from the linear relationship between the hydrogen flux and the hydrogen concentration difference. It is found that the hydrogen diffusion coefficient of pure Nb is much lower than the reported values measured for dilute hydrogen solid solutions. Surprisingly, the hydrogen diffusion is found to be faster in Pd-26 mol%Ag alloy with fcc crystal structure than in pure niobium with bcc structure at 773 K during the hydrogen permeation. It is also interesting that the addition of Ru or W into niobium enhances the hydrogen diffusion of the practical hydrogen permeation at high temperature.

The morphology and crystallography of eutectic structures in several niobium-bearing hydrogen permeation alloys such as Nb₂₀Ti₄₀Ni₄₀, Nb₃₀Ti₃₅Co₃₅, Nb₁₃Zr₄₃Ni₄₄, and Nb₂₅Zr₃₅Co₄₀ have been investigated by means of transmission electron microscopy. The alloys Nb₂₀Ti₄₀Ni₄₀, Nb₃₀Ti₃₅Co₃₅, and Nb₂₅Zr₃₅Co₄₀ possess eutectic structures consisting of fine lamellar morphology with Nb-based bcc and B2 intermetallic phases. The Nb₁₃Zr₄₃Ni₄₄ alloy possesses a eutectic structure consisting of rod-shaped bcc-(Nb, Zr) phase and B33-ZrNi phase which displacively transforms from the B2 high-temperature phase. The eutectic structures in the Nb₂₀Ti₄₀Ni₄₀ and the Nb₂₅Zr₃₅Co₄₀ alloys exhibit a cube-on-cube orientation relationship between the bcc and B2 phases. The eutectic structure in the Nb₁₃Zr₄₃Ni₄₄ alloy also exhibits a cube-on-cube orientation relationship by considering the lattice correspondence between the B2 and the B33 structures. On the other hand, a unique orientation relationship is found out in the Nb₃₀Ti₃₅Co₃₅ alloy, as follows: (110)_{(Nb, Ti)}||(110)_TiCo, [\\bar221]_{(Nb, Ti)}||[001]_TiCo. The atomic arrangements at the eutectic interface are also discussed on the basis of high-resolution observations.

A series of Nb₄₀Ti_30+xNi_30−x alloys are characterized in terms of microstructure, crystal structure, ductility, susceptibility to hydrogen embrittlement, and hydrogen permeability as non-palladium-based hydrogen permeation alloys. The maximum hydrogen permeability and ductility of the alloy is exhibited by the alloy with composition of x=2 (Nb₄₀Ti₃₂Ni₂₈). The enhancement of hydrogen permeability correlates well with an increase in the volume fraction of the primary (Nb, Ti) phase. After cold rolling and annealing, the hydrogen permeability of the Nb₄₀Ti₃₄Ni₂₆ (x=4) alloy becomes superior to that of the Nb₄₀Ti₃₀Ni₃₀ (x=0) composition previously reported to be the best in the Nb₄₀Ti_30+xNi_30−x series. The present results indicate that the hydrogen permeability of the Nb-TiNi alloy can be optimized by annealing and appropriately adjusting the Ti/Ni ratio for a given niobium content.

A series of Nb₄₀Ti_xZr₁₂Ni_48−x alloys with different Ti/Ni ratios were prepared by arc melting in a purified argon atmosphere. The Ti/Ni ratio affected microstructures, crystal structures, ductility and hydrogen permeability (Φ) of these alloys. The values of hydrogen permeability Φ for the Nb₄₀Ti_xZr₁₂Ni_48−x alloys increased with increasing temperature and were higher than those of pure Pd above 573 K. Hydrogen permeability at 673 K, i.e., Φ_673K and the volume fraction of the primary phase in the Nb₄₀Ti_xZr₁₂Ni_48−x alloys increased with increasing Ti/Ni ratio. The present work demonstrated that hydrogen permeation properties of the Nb₄₀Ti₂₀Zr₁₂Ni₂₈ alloy are superior to those of the Nb₄₀Ti₁₈Zr₁₂Ni₃₀ one which was reported to be the best one in the Nb₄₀Ti_30−xZr_xNi₃₀ alloys.

A single phase Mg(BH₄)₂ was successfully synthesized and its hydrogen storage properties were systematically investigated. Depending on the synthesis conditions, Mg(BH₄)₂ forms low- and high-temperature phases with different crystal structures. The dehydriding reaction of Mg(BH₄)₂ starts at approximately 500 K, and 14.4 mass% of hydrogen is released through a multi-step reaction. Furthermore, 6.1 mass% of hydrogen can be rehydrided for the sample of Mg(BH₄)₂ after the dehydriding reaction, through the formation of a possible intermediate compound such as MgB₁₂H₁₂.

The effects of the partial substitution of Y for La in La_1−xY_xNi_3.55Mn_0.4Al_0.3Co_0.75 (x=0, 0.1 and 0.2) alloys were reported in this paper. The single-phase CaCu₅-type structure is retained after La is partially substituted by Y. However, the increase of Y content leads to decrease of the lattice parameters and unit-cell volume. Y substitution for La in the alloys is effective to improve the electrochemical properties at room temperature and high temperature. A critical substitution content of Y is found at x=0.1.

When the polished Ni-Ti alloy plates were hydrogen charged cathodically, it was newly found that the plates were bent spontaneously as the hydrogen charging time increased. The degree of the spontaneous bending was closely related to the structural change on the surface of the plates. When only one side of the specimen surfaces was polished by an emery paper or buffed, the spontaneous deformation was clearly identified after hydrogen charging. In contrast, when both sides of the specimen surfaces were polished in the same level, such deformation was not observed. Thermal hydrogen desorption analysis showed that the degree of the spontaneous bending was clearly related to the difference of the hydrogen concentration, probably in the thickness direction. It was also found that when hydrogen was released from the specimen by heating, the spontaneous bending was disappeared. Based on the X-ray diffraction analysis of the polished specimen surfaces before and after hydrogen charging, it was revealed that the amount of hydrogen entered into the specimen was promoted by the polishing because of the crystal lattice distortion and the strain-induced martensite transformation.

Effect of hydrogen charging on mechanical properties in tensile and fatigue tests was investigated for the Ni-Zr amorphous alloy membranes with and without palladium plating. As a result of the tensile test, it was shown that both tensile strength and fracture strain decreased by continuous hydrogen charging in all the specimens. It was also found that palladium plating reduced effectively the hydrogen embrittlement sensitivity. Fatigue properties were also lowered by hydrogen charging. In the specimen without hydrogen charging, fatigue limit was about 600–700 MPa, while in the specimen with hydrogen charging, no clear fatigue limit was observed. Fracture morphology was changed from the vein-like patterns to the shell patterns by hydrogen charging, both after the tensile test and the fatigue test.

Stress-controlled fatigue tests were performed for 5% and 15% cold-worked 304 stainless steels under in-situ irradiation with 17 MeV protons at 300°C. Increase of fatigue life with prolonged crack propagation length under in-situ irradiation was detected for 5% cold-worked specimens, whereas no significant difference was observed in fatigue life or crack propagation length between in-situ irradiation and unirradiated conditions for 15% cold-worked specimens. Fractographic analysis of the fatigue fracture surface suggested more significant participation of strain-induced martensite in fatigue behavior for 15% cold-worked specimens. The strain-induced martensite in 15% cold-worked specimens would play an important role in reducing the in-situ irradiation effect on fatigue behavior based on the interaction between radiation-induced defect clusters and moving dislocations.

Mg-Y-Zn alloys have attracted much attention in recent years due to their excellent mechanical properties, which are said to be the effect of the intermediate phase (X phase) in the Mg solid solution (α phase). The formation behavior of the X phase has been reported to be a eutectic type reaction in the Mg-Y-Zn pseudo-binary system. However, the phase diagram of this system still requires clarification. In the present study, the 97.0Mg-1.3Zn-1.7Y (at%) alloy was prepared to clarify the liquidus and solidus in the liquid-solid coexistence region, and the solubility limit in the α phase. The chemical compositions of the alloy were analyzed by electron probe X-ray microanalysis after isothermal heat treatment. The results indicate that the Mg-Y-Zn ternary system can be represented as a pseudo-binary system between the α and X phases. In addition, the solidus line for the α phase has been clarified. The solubility limit for the α phase is not much different from that of the previous report, whereas the formation behavior of the X phase is not in the manner of a eutectic reaction, but rather that of a peritectic one.

The L_I and L_III edges of Hg and the K edge of Rb in liquid Hg-Rb alloys were measured by the absorption spectroscopy of X-rays. On increasing the Rb concentration, the absorption edges of Hg show an opposite behavior each other, the decrease of L_I and the increase of L_III compared with the case of pure liquid Hg. This difference was discussed from the polyanion formation of Hg atoms on alloying. With the increase of alkali concentration, the p like state or polyanion seems to be situated on the lower energy side than that of s band. The electronic structure of this polyanion was discussed based on a simple LCAO analysis. Such an existence of polyanions may be responsible to the curious phenomena of liquid Hg-alkali alloys, the maximum of the electrical resistivity at 60 at% alkali and the positively enhanced tendency in the intermediate alkali concentration range of the magnetic susceptibility in the overall negative deviation.

Tungsten-based model alloys were fabricated to simulate compositional changes by neutron irradiation, performed in the JOYO fast test reactor. The irradiation damage range was 0.17–1.54 dpa and irradiation temperatures were 400, 500 and 750°C. After irradiation, microstructural observations and electrical resistivity measurements were carried out. A number of precipitates were observed after 1.54 dpa irradiation. Rhenium and osmium were precipitated by irradiation, which suppressed the formation of dislocation loops and voids. Structures induced by irradiation were not observed so much after 0.17 dpa irradiation. Electrical resistivity measurements showed that the effects of osmium on the electrical resistivity, related to impurity solution content, were larger than that of rhenium. Measurements of electrical resistivity of ternary alloys showed that the precipitation behavior was similar to that in binary alloys.

A permeable reactive barriers (PRBs) column test was carried out to remove arsenic (As) and manganese (Mn) from groundwater using zero valent iron (ZVI), sheep manure, compost and woodchips as reactive materials. Arsenic was mainly immobilized through sorption and co-precipitation with iron-bearing minerals, and also possibly precipitation as FeAsO₄. The presence of sulfate-reducing bacteria (SRB) in the inoculated column was suggested by decrease of sulfate concentrations and increase of δ³⁴S in the effluent. Arsenic was more effective to immobilize in the inoculated than in the sterilized column due to co-precipitation with sulfides formed by reduction of sulfate in addition sorption and/or co-precipitation with carbonates. The Mn was mainly immobilized through adsorption onto compost and ZVI, and partly by precipitation as carbonates. Manganese was more effectively immobilized in the sterilized than in the inoculated column. Since compost is biodegraded, the capability of compost to immobilize Mn²⁺ decreased in the inoculated column. The result demonstrates that As is more effective to immobilize using mixture of sheep manure with ZVI than only ZVI as reactive materials in PRBs.

Permeable reactive barriers (PRBs) column tests were performed to investigate the contribution of anaerobic microbial community in sheep manure on the removal of As from groundwater. The column was packed with zero valent iron (ZVI), sheep manure, compost, wood chips, glass beads and gravels. All materials were sterilized except for sheep manure that contains anaerobic bacteria. Decrease in sulfate concentration was observed at the maximum rate of 0.26 mmol dm⁻³ day⁻¹. In addition, the sulfur isotopic ratio of δ³⁴S increased from the influent (−4.3\\ extperthousand) to the effluent (0.2\\ extperthousand), suggesting that there was sulfate-reducing activity in the microbial community. Arsenate was more effectively immobilized on ZVI than arsenite. Bacterial community analysis using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) on 16S rRNA sequences suggested that majorities of bacteria were several Clostridium species and one species of Proteobacteria, Geobacter metallireducens GS-15, independently of PRBs column heights. Some of them might have contributed to the removal of arsenic.

The resistivity-temperature curve of 7050 aluminum alloy prepared in different casting methods (DC and LFEC) has been measured with D.C. four-probe method. By analyzing the curve, it was found that a change occurred to the slope at 250°C when the samples were heated, and the resistivity of LFEC sample changed with temperature more quickly than that of DC. Both the solidus and liquidus temperatures of LFEC samples were higher than those of DC samples during the process from room temperature to 900°C. However, the resistivity of DC samples increased remarkably while the temperature was kept at 900°C, and even before it was decreased to 600°C. With the microstructure observation, the characteristics and phenomenon of the resistivity evolution with temperature were studied.

These vertically aligned Ta₂O₅ nanorods were deposited on Si (100) substrates by thermal deposition in a vacuum of the order of 10⁻² Torr at about 600°C. When excited by 514 nm Ar⁺ laser, they showed a strong photoluminescence at ∼622 nm, which was attributed to the oxygen vacancies. In addition, their dielectric constant is ∼20 in the frequency range from 1 kHz to 10 MHz, far larger than that of SiO₂ and Si₃N₄. Due to this cone-shaped morphology, the Ta₂O₅ nanorods exhibited a threshold field of ∼8.5 V/μm in field emission and a field enhancement factor of 764 that are sufficiently high for field emission application.

A new approach on the modelling of isothermal recrystallisation in cold rolled ferritic steels based on Avrami equation is presented here. The new model corrects some of the fundamental shortcomings of the classical JMAK modelling, such as non-random (clustered) nucleation and decreasing grain growth velocity. It is shown that the new model successfully predicts the recrystallisation degree of the deformed material during an isothermal annealing, depending on the cold rolling grade and annealing conditions. Finally, an application for back annealed cold rolled steels is illustrated.

In Sn-2 mass%Ag-0.5 mass%Cu solder alloy, recrystallization was induced by thermal cycles and the homogenized effect of thermal aging promoted the vibration resistance. Due to the inner stress induced by thermal cycles, the thermal cycle specimen not only possessed a finer structure but also a large number of grain boundaries that were able to increase the vibration life. During vibration, dynamic recrystallization (DRX) was able to occur. In addition, DRX and grain growth had an obvious tendency to increase as the tensile strain rate was increased in the Sn-1 mass%Ag-0.5 mass%Cu solder alloy with a high β-Sn content. Also, high temperatures and plastic deformation had a significant influence on the recrystallization of the solders.

The effects of carbon and/or alkaline earth elements Ca and Sr on the grain refinement and tensile properties of the AZ31 alloy have been investigated in the present study. A significant grain refining efficiency could be obtained for the AZ31 alloy modified by carbon inoculation and the grain refining efficiency could be further improved by the combination of 0.2 mass%C and alkaline earth elements of 0.2 mass%Ca or 0.2 mass%Sr. Compared to the AZ31 alloy without any treatment, the tensile properties of the AZ31 alloy were remarkably improved after being modified by the combination of carbon and a little addition of alkaline earth elements. The ultimate tensile strength and elongation to failure were improved by about 20% and 40%, respectively. After being refined either by 0.2 mass%C or by the combination of 0.2 mass%C and a little addition of alkaline earth elements (0.2 mass%Ca or 0.2 mass%Sr), the main fracture mechanism was changed from cleavage mode with large cleavage planes for the unrefined AZ31 alloy to mixed mode of cleavage and quasi-cleavage fracture. The fracture surfaces were almost composed of small cleavage planes with thin river patterns and quasi-cleavage planes with small dimples and severe plastic deformation.

CaSiO₃/Ti₃SiC₂ composites with different Ti₃SiC₂ volume fractions were fabricated by spark plasma sintering. The mechanical properties and hydroxyapatite formation ability in simulated body fluid were investigated. The results showed that no reaction occurred between the CaSiO₃ and Ti₃SiC₂, and mechanical properties were improved significantly with the increase of the Ti₃SiC₂ volume fraction. Bending strength and fracture toughness reached 271±12 MPa and 2.47±0.17 MPa·m^1⁄2 respectively, with the addition of 30 vol% Ti₃SiC₂. However, bioactivity is reduced due to the presence of large amount of Ti₃SiC₂. In order to retain the enough bioactivity, the Ti₃SiC₂ volume fraction should not be above 30%.

The effects of vacancies on deformation of nanocrystalline Ni have been investigated by experiments and molecular dynamics (MD) simulations. In the experiments, nanocrystalline Ni specimens containing different numbers of vacancies were produced by electrodeposition and annealing, and their mechanical properties were investigated by tensile tests. As a result, the yield stress and fracture stress for the specimen containing more vacancies were lower than those for the one containing fewer vacancies. The MD simulations showed that the grain boundary energy is increased by the presence of vacancies in the grain boundary, however, that an increase in grain boundary energy with straining is reduced by the presence of vacancies in the grain boundary. The results of the experiments and simulations suggested that there is a correlation between the grain boundary energy characteristics and the mechanical properties of the nanocrystalline Ni.

Hypoeutectic cast irons containing 16 mass% and 26 mass% Cr with single additions of Ni, Cu, Mo and V as well as without alloy addition were prepared to investigate variations of micro-hardness of matrix during heat treatment. In the as-hardened state, Ni and Cu decreased the micro-hardness but Mo increased it slightly. By contrast, V increased the micro-hardness in 16 mass% Cr but reduced it in 26 mass% Cr cast irons. The volume fraction of retained austenite (V_γ) was positively correlated with alloy content except for V addition and it was high at elevated austenitizing temperatures. Tempered micro-hardness curves showed secondary hardening and the degree of secondary hardening (ΔH_D) was greater in alloyed specimens comparing with alloy-free specimen. The ΔH_D was closely related to V_γ in as-hardened state, and the more the V_γ, the greater the ΔH_D. The maximum tempered micro-hardness (H_MTmax) was obtained in the specimen tempered at 698 to 873 K depending on the kind and the amount of alloying element where the V_γ was less than 20%. The H_MTmax values of Mo and V containing specimens increased with the V_γ in the as-hardened state. The highest value of H_MTmax was obtained in those samples containing 3 mass% Mo in both series of the cast irons. The mechanism of secondary hardening in Mo and V containing cast irons was mainly by both the precipitation of special secondary carbide and the transformation of destabilized as-hardened retained austenite into martensite providing the high micro-hardness.

This work addresses at the development of the use of interlayer of different materials for TiB₂ coatings with increased adhesion to the substrate and retained high hardness. Ti and Cr were deposited on stationary high speed steel and silicon wafer substrates by magnetron sputtering as an interlayer material. The resultant coatings were evaluated with respect to fundamental properties such as structure, coating roughness, hardness, modulus and adhesion. It was found that the adhesion of resultant TiB₂ coatings was increased tremendously with Cr interlayer, whilst the hardness was slightly increased.

TiB₂-TiC-Ti₃SiC₂ composites were reaction-sintered from B₄C-xSiC-(3+2x)Ti (x=0 to 1) powder mixtures using reactive hot pressing, and the phase relation of reaction products and sintering behavior were investigated. The reaction B₄C+xSiC+(3+2x)Ti→2TiB₂+(1−x)TiC+xTi₃SiC₂ proceeded fundamentally during hot pressing. Although the reaction demands no production of TiC phase at x=1, TiC phase was formed due to the nonstoichiometry of TiC and Ti₃SiC₂ phases produced. The hot-pressed composites containing the layered compound Ti₃SiC₂ had no preferential texture. Both TiB₂ and TiC were first produced near 960°C during heating, and then Ti₃SiC₂ near 1200°C. The product Ti₃SiC₂ contributed effectively to the densification of the composites above 1450°C.

A unique behavior of acoustic signals occurred for each type of defect as evident in their respective time and frequency domains. Straight pinhole shows that the faster the gas leakage passes through the defect the greater the magnitude of amplitude of the generated AE signals was recorded. Scattered AE signals took place above the critical pressure due to large scale flow instability. For stepwise pinhole, the magnitude of amplitude is higher for a thicker wall dimension and has a common characteristics with a sudden dropped of amplitude over the transition of flow. In a similar manner, the cone-type pinhole shows other distinct characteristics for two different dimensions. When pressure is over 370 kPa unusual sound is generated for 1.0 mm wall thickness. On the other hand, only straight pinhole shows a decreasing peak frequency after reaching the critical pressure, which is attributed to screech tone characteristics. While for stepwise pinhole with 1.0 mm wall thickness, the peak frequency is generally higher compared with 2.0 mm wall thickness. The cone-type orifice have similar pattern with stepwise pinhole in terms of peak frequency. Generally, the dissimilarity of AE generated signals revealed a distinct characteristic for every type of pipe defect. And the effect of stepwise deviation is extremely obvious in various depths.

The characteristics of the crescent bond process with insulated Au wire are investigated. Au wire with a sub-micron thick insulation coating is bonded on standard Ag plated leadframe diepads at 493 K. The wire loops are oriented perpendicular to the ultrasonic horn. The pull force obtained with a basic bonding process of insulated Au wire and bare Au wire are optimized by iteration and compared. Subsequently, the process is modified for the application with insulated wire. To increase the pull force an insulation layer removing stage (cleaning stage) is inserted before the bonding stage. The cleaning stage consists of a scratching motion (shift) toward to the ball bond in combination with ultrasound. The pull force obtained in this way with the insulated wire is 90.1±7.9 mN which is 2.4±2.0 mN larger than that obtained with bare Au wire.

A combination of X-Ray Magnetic Circular Dichroism and PhotoEmission Electron Microscopy (XMCD-PEEM) was applied to the magnetic domain analysis of Nd-Fe-B sintered magnets. The XMCD-PEEM high-resolution images revealed both the magnetic domain structures and the microstructural morphologies. In the thermally demagnetized state, each grain in a polycrystalline sample exhibits a multi-domain structure, which is magnetically coupled across grain boundaries. After the DC field-demagnetization, it changed to a single domain structure. The magnetization vector in each surface grain reversed to the negative direction during the field-demagnetization procedure because of the small coercivity in the surface region. In the present study, we observed this surface domain reversal for the first time by means of XMCD-PEEM imaging method, which is important in order to understand the surface phenomena of Nd-Fe-B magnets.

An Ag-Pd-Cu-Au casting alloy was subjected to solution treatment at various temperatures. The dynamic hardness of each resultant microstructure and the Vickers hardness of the whole alloy were measured to investigate their relationship with changes in metal and crystal structure of the alloy and microstructural elemental concentration. The samples following solution treatment at 650, 700, 750, and 800°C consisted of a fine-layer structure (Structure A), a rough-layer structure (Structure B), and an island-like structure (Structure C). Structures A and B, after treatment at 850°C, were indistinguishable. The composition of Structure A was very similar to that of the alloy. Structures B and C were Ag-rich/Pd-poor/Cu-poor and Ag-poor/Pd-rich/Cu-rich, respectively. The composition of Structures B and C approached that of Structure A with increasing treatment temperature. The dynamic hardness, which was highest in Structure A, lower in Structure C, and lowest in Structure B, increased with increasing treatment temperature. These findings suggest that solid solution strengthening, due to elemental diffusion between structures during heating, contributes to hardening at elevated solution treatment temperatures.

The objective of this study is to promote understanding of the structural evolution of fractures that affect the transport of contaminants in geological media. Highly soluble potassium alum was used as an analogue material, and was grown in an open fracture from a solvent transported by advection along the fracture, in order to observe decreases in the aperture of the fracture. In addition, the growth rate law of K-alum was experimentally determined based on the relationship between relative supersaturation and linear flow velocity. The sealing result was compared with simulations based on a simplified numerical model using the experimentally determined growth rate law, and it was found that the time necessary for sealing was longer for the simulation than for the experimental sealing. This discrepancy was explained by the additive growth rate of the original seed crystal and secondary crystals nucleated near the fixed seed crystal. Thus, it was shown that primary and/or secondary nucleation is an additional factor for prediction of the structural evolution of fractures in geological media.

This study investigated the effect of the addition of wetting agents on automobile shredded residue (ASR) wettability, and found that the surfactants diisooctyl sodium sulfosuccinate (AOT) and sodium dodecyl sulfate (SDS) were effective to improve immersion of the ASR, due to their ability to reduce the solution surface tension and the contact angle of ASR. Urethane foam is a bulky compound in ASR and its immersion and wetting behavior showed similar changes as those of the ASR samples. With SDS the surface wettability of urethane was improved. The surfactant solutions were also effective in the detachment of the entrapped particles from the agglomerate of entangling fiber like materials. The effects of the surfactant concentrations on ASR wettability and the amount of detached particles are described.

The biodegradable chelating agents [S,S]-ethylenediaminedisuccinic acid (EDDS), citric acid and the low biodegradable chelating agent ethylenediaminetetraacetic acid (EDTA) were investigated for their applicability for the removal of lead from soil by soil washing and electrokinetic processing.
In the soil washing tests at 298 K, the removal efficiency of lead with EDDS and EDTA was high in the pH range from 7 to 10 and the ability of lead removal with EDDS in this pH region is comparable to that with EDTA. Meanwhile, the removal efficiency of lead with citric acid was approximately 50% at pH 4 and decreased with increasing pH. Therefore, citric acid was hardly useful. Acid contribution was predominant for the removal of lead with EDDS and citric acid at pH 4 and the complexation between these chelating agents and lead were negligible.
In the electrokinetic tests at ambient temparature, EDTA was more effective than EDDS and citric acid for lead transport through the soil by electrokinetic processing.

This paper describes studies on the recovery of metals from spent hydro-processing catalyst using mixed acidophilic culture in presence of pyrite. This culture was initially grown in the 9K⁻ medium (absence of 9 g/L Fe(II)) where ferrous sulphate (FeSO₄) was replaced by pyrite, and then applied in this bioleaching study. Bacterial action on pyrite catalysed the formation of ferric ion (Fe⁺³), proton (H⁺) and sulphate ions (SO₄⁻²) in the solution which leached metals (Ni, Mo and V) from the spent catalyst. Experiments were conducted by varying the reaction time, amount of spent catalyst and pyrite, and temperature. After 7 days with 30 g/L of spent catalyst and 50 g/L of pyrite, the leaching of Ni, V and Mo into the solution was 85, 92 and 26%, respectively. With increasing spent catalyst loading, the extent of metal dissolution was decreased, probably due to the precipitation of Fe⁺³ as a residue. Under all conditions tested, Mo showed recovery due to its precipitation with leach residues as MoO₃ observed by applying EDAX and XRD techniques to the leach residues.

The aim of the work described in this paper was to establish the effect of physical parameters such as pH and temperature on the microbial growth and iron oxidation rate of an isolated iron oxidizing bacterial strain from mine effluent. The bacterial lag phase was reduced to zero by repeated subculturing in fresh nutrient media. The rate of iron oxidation was considered as the growth rate of the microorganism in its logarithmic phase. Variation of pH showed an inadequate effect within the range from 1.5 to 2.5 ensuing growth flexibility in acidic medium. With variation of temperature from 293 to 313 K, the rate increased up to 303 K and gradually decreased beyond this temperature. At the optimized values of pH 2.0 and temperature 303 K, the iron oxidation rate was 2.17×10⁻⁴ kg·m⁻³·s⁻¹.

In order to develop a process to obtain a functional layer on the surface of a magnesium alloy, the composite layer including in situ Mg₂Si was formed on the surface by a gravity die-casting. The optimum fabrication condition to form the composite layer and the formation mechanism of the layer were clarified by observing the microstructure, and then the wear properties of the composite layer were also investigated. By casting the magnesium alloy melt into the permanent mold on which the slurry mainly consisting of Si particles was coated, the magnesium alloy composite layer in which the in situ Mg₂Si particles were dispersed was formed. The melt temperature and mold temperature required to form the composite layer, which perfectly covers the casting, were above 1073 K and above 673 K, respectively. The composite layer was a magnesium alloy in which the fine Mg₂Si particles of approximately 40 vol% were dispersed. The thickness and hardness of the layer was about 600 μm and 180 HV, respectively. Under the dry sliding wear, the weight loss of the composite layer was lower than that of the magnesium alloy. These results lead to the conclusion that the wear resistant magnesium alloy composite layer in which the in situ Mg₂Si particles were dispersed can be formed in the present process.

Aluminum alloy composites reinforced with short potassium titanate fibers were fabricated by squeeze casting, and the effect of the fiber reinforcement on the machinability of the alloy under various cutting conditions were investigated. The fibers were randomly arranged in the alloy matrix, and no agglomeration of the fibers or porosity was observed. Although the cutting force of the AC4A alloy decreased as the cutting speed increased, that of the composites little changed even though the cutting speed increased. When the cutting speed was 50 m/min, the cutting force of the AC4A alloy significantly decreased due to the fiber reinforcement. When the cutting speed was 100 and 150 m/min, the cutting force of the composites was equivalent to or less than that of the AC4A alloy. The variation in the fiber volume fraction only slightly affected the cutting force values of the composites. The roughness of the machined surface of the AC4A alloy increased as the feed rate increased, and decreased as the cutting speed increased. The fiber reinforcement diminished the variation in the roughness due to the feed rate and cutting speed. When the feed rate was high, the roughness of the composite having a high fiber volume fraction was almost equivalent to the theoretical roughness. This indicates that the fiber reinforcement suppresses the formation of the built-up edge. The machined surface and chip forms indicated that the fibers in the composite facilitated the shear deformation of the chips because the fibers were easily sheared by the cutting. These results lead to the conclusion that the machinability of the composite is superior to that of the AC4A alloy.

The effect of microstructural evolution on the creep properties in Mg-Sn-Ca system has been investigated. As-cast microstructure of Mg-Sn-Ca alloy consists of two or three phases depending on the Ca/Sn ratio, i.e. Mg₂Sn, CaMgSn and Mg₂Ca phases. Ternary CaMgSn phase has two types of morphology by its pseudo hyper-eutectic reaction with α-Mg; coarse rod-like primary or feather-like eutectic phase. Primary solidified CaMgSn phase exhibit negative effect on the tensile properties in spite of its high thermal stability up to 500°C. According to the creep test results, apparent stress exponent value (n=7) indicates climb controlled creep mechanism by core diffusion above 150°C. Activation energy of Mg-5Sn-2Ca alloy (74 kJ/mol) is close to grain boundary diffusion for pure magnesium, 92 kJ/mol. Creep resistance is remarkably improved with the presence of Mg₂Ca phase.