Quantitative X-ray structural analysis using an in-house X-ray diffraction apparatus has been used for characterizing the atomic-scale structure of the γ-FeOOH (lepidocrocite) particles prepared by dipping a pure iron and an iron-silicon alloy into aqueous solutions containing sodium chloride. The morphology of the γ-FeOOH particles was observed by transmission electron microscopy (TEM), and their bonding structure were analyzed using Fourier transform infrared spectroscopy (FT-IR). The realistic atomic-scale structures in the γ-FeOOH particles were estimated by fitting the interference functions with the help of the reverse Monte Carlo (RMC) simulation technique. The results showed that the linkages of fundamental FeO₆ octahedral units in the particles were deviated from the ideal crystal structure. The structural deviation is considered to be due to the incorporation of foreign ions during the formation of these particles in the aqueous solutions.

In order to improve high-temperature oxidation resistance of titanium, fabrication of TiAl intermetallic compounds as a surface layer by plasma transferred arc surfacing (PTA surfacing) was investigated. Powder of unalloyed aluminum was fed into the plasma during the PTA surfacing and TiAl-based intermetallic layers were successfully synthesized. The surface layers had no cracks and porosities with optimized conditions of the PTA surfacing. The surface layers that largely consist of TiAl and Ti₃Al phase could be achieved, while the microstructures of them were significantly influenced by the conditions such as the arc current. The TiAl-based layers exhibited high resistance to oxidation under isothermal conditions at 1073 K or less and had practically the same resistance as SUS310S had.

The dc electrical conductivity, σ_dc, was measured for liquid (AgI)_x–(Ag₂O)_y–(B₂O₃)_1−(x+y) (x=0.7–0.9; y=0.05–0.2) by using an ac impedance method in particular concern with the precipitation mechanism in the α-AgI precipitated glass, which was prepared by a rapid quenching technique due to a twin-roller apparatus. The temperature dependence of σ_dc exhibits two inflexion points. The existence of two liquid phase separation was confirmed by the electrical conductivity measurements with the use of specially designed cell. In addition, the X-ray diffraction and the SEM (Scanning Electron Microscope) experiments were performed for the rapidly quenched samples. The α-AgI precipitated glass was obtained by adopting the higher holding temperature even for the composition for which the β-AgI precipitated glass was prepared in the case of a lower holding one. These results indicate the role of two liquid phase separation on the preparation process of nano α-AgI crystallites in the glass matrix.

Single-layer Pd membrane with the thickness of about 2.5 μm was successfully prepared by microfabrication technology. Hydrogen permeation of the as-prepared Pd membrane was investigated in the temperature range of 473–673 K under hydrogen transmembrane pressure of ∼40 kPa. Hydrogen permeation of Pd membrane with the thickness of 0.70 mm was also carried out for comparisons. It was found that the hydrogen permeability of the 2.5 μm-thick Pd membrane was about half of that of the 0.7 mm-thick Pd membrane. Surface resistance was less significant in hydrogen permeation through the thin microfabricated Pd membrane than thin Pd membranes supported by porous materials. Grain growth was observed in the thin microfabricated Pd membrane upon hydrogen permeation.

Transmission electron microscopy observation of cross-sectional specimens prepared by focused ion beam milling method have been applied to study the deep radiation damage and depth profile of point defects generated during ion irradiation in Cu–1 mass%Co alloy specimens by means of coherent precipitates. The specimens were irradiated at a temperature range of 250 to 500°C by 4 and 0.6 MeV self Cu ions to a dose of 0.3 dpa. The damage range has been observed at depths well beyond that expected from ion damage range calculations.

The preparation process of white heart malleable cast iron in Na₂O–SiO₂ oxide molten salts was studied. We investigated the effect of the molten salt composition on the decarburization of white cast iron. A specimen of white cast iron (φ8mm×8mm) containing 3.34 mass% carbon was immersed in a Na₂O–SiO₂ molten salt at 1323 K for 24–72 h. After the heat treatment of white cast iron in Na₂O–SiO₂ (64–36 mol%) at 1323 K for 48 h, low-carbon surface layer had a thickness of about 100 μm and contained 0.53 mass% carbon. This surface layer was formed as a result of the reaction of carbon in white cast iron with free oxygen in the oxide molten salt. However, no decarburized layer was observed on the specimen surface after the heat treatment in the Na₂O–SiO₂ (38–62 mol%) molten salt. As the Na₂O composition increased within the limit of 41 < Na₂O (mol%) ≤ 65, the thickness of the decarburized layer also increased. It was found that white heart malleable cast iron could be prepared from white cast iron in Na₂O–SiO₂ oxide molten salts, and the degree of decarburization depended on the composition of the molten salts.

The microstructure of a mechanically finished calcium fluoride (CaF₂) was studied by transmission electron microscopy (TEM). The (111) oriented surfaces of high-purity CaF₂ single crystals were finished to a flat surface by ultra-precision mechanical polishing. A float polishing method—with 7-nm-diameter silicon dioxide powder, pure water, and a tin lap—was employed for the finishing. Prior to the float polishing, ultraprecision grinding was performed as the preliminary treatment. A cross-sectional TEM study indicated that the thickness of the subsurface damage introduced by ultraprecision grinding was relatively small when compared with that by the conventional optical polishing process. Further, the float polishing process did not introduce any mechanical damages in the CaF₂ crystals. The TEM images showed that the float-polished surface had a faceted structure consisting of (111) terrace planes and nanometer-sized steps. The size of a single terrace depends on the mismatch angle between the sample surface and the (111) plane. The high-resolution TEM observation suggested that an atomically smooth (111) surface with a bulk fluorite structure was obtained over a relatively wide area on the large terrace planes.

The average and local structures in the (Ti_0.45Cr_0.35Mo_0.20)–D system have been investigated by neutron powder diffraction and total neutron scattering. From the result of neutron powder diffraction, the crystal structure of the system was found to change from CaF₂-type structure to bcc structure in the hydrogen desorption process, and the D atoms occupy the tetrahedral (T) sites in both CaF₂-type and bcc phases. The D–Ti, D–Cr, D–Mo and D–D correlation lengths and the nearest neighbor coordination number around a D atom have been obtained by the RDF analysis of total neutron scattering data. The D atoms occupy the T sites surrounded mainly by the Ti atoms in both CaF₂-type and bcc phases.

Mechanical alloying and pulsed-current sintering were used to synthesize TiB₂–Fe–Al cermet alloys consisting of titanium boride and iron aluminide intermetallic compound. A mixture was obtained to which Fe was minutely distributed by mechanically alloying TiB₂ powder and Fe powder for 180 ks. Mixture powders of TiB₂–20 mass%Fe₃Al and of TiB₂–24 mass%FeAl were prepared by mixing an Al powder with this mechanically alloyed powder using a mortar. The added Al reacted with Fe after it had melted when these mixtures were heated. These powders were sintered for a short time and at low temperature using pulsed-current sintering process, but these sintered compacts had pores.
Several iron aluminide intermetallic compounds were generated in the TiB₂–20 mass%Fe₃Al. Therefore, the TiB₂–20 mass%Fe₃Al compact was hard and brittle. However, the TiB₂–24 mass%FeAl sintered body was composed only of TiB₂ and FeAl, and had better ductility. A slight weight increase resulted from oxidation even though it was heated to 800 K or more in the air, but both sintered compacts retained their pores.

Hf films have been deposited on Si(100) substrate with or without a substrate bias voltage using a non-mass separated ion beam deposition (IBD) method. Secondary ion mass spectrometry (SIMS) and glow discharge mass spectrometry (GDMS) have been used to determine impurity concentrations of Hf films and a Hf target. By the SIMS results with Cs⁺ and O₂⁺ ion beams, the Hf film deposited at V_s=0 V contains more impurities than the Hf film deposited at V_s=−50 V. In addition, from GDMS results for the Hf target and the Hf films deposited at V_s=0 and −50 V, almost all the impurities have reduced by applying a negative substrate bias voltage. It means that applying a negative bias voltage to the substrate can decrease the impurity concentrations in Hf films.

Porous Co–29Cr–6Mo (mass%) compacts without Ni were fabricated by hot pressing and their microstructure and mechanical properties were investigated. PREPed Co–29Mo–6Mo powder with a diameter range (300–500 μm) was hot-pressed under the uniaxial pressure of 40 MPa at 1223 K for 7.2 ks. Hot-pressed compacts were annealed at 1473 K for 7.2 ks for further sintering. X-ray diffraction analysis revealed that γ and ε phases appeared dominantly in the PREPed powder, while ε and σ phases coexisted in the compact which was hot-pressed at 1223 K. After annealing at 1473 K, only the ε phase was detected although the γ phase was stable at this temperature. Therefore, the ε phase formed during furnace cooling.
Tensile behavior of porous Co–29Cr–6Mo compacts was characterized by the stress–strain curves. The as-hot pressed compact showed linear deformation followed by sudden fracture. The annealed compact showed higher ultimate tensile strength (UTS) and lower yield strength than the as-hot pressed compact. Young’s modulus of the annealed compact was difficult to determine from the stress–strain curve. However, the annealed compact possessed a tensile strength of 116 MPa, which is comparable to that of human cortical bone.

The wrought Co–Cr–Mo alloys with C contents of 0.02, 0.09 and 0.18% (mass%) were fabricated by hot-forging process to study the influence of carbon contents on the microstructures and mechanical properties. The microstructures of Co–29Cr–6Mo–0.02C and Co–29Cr–6Mo–0.09C consist of equiaxed uniform grains which contain stacking faults, twins and ε martensite bands. No carbide found at inter- and intra-granular region. Co–29Cr–6Mo–0.18C consists of irregular grain sizes and carbide found at inter- and intra-granular region. The carbide in Co–29Cr–6Mo–0.18C was identified as M₂₃C₆ type carbide from the XRD pattern analysis. It is found that the amount of stacking fault and ε martensite are strongly dependent upon the C content. The density of stacking faults and ε martensites observed in Co–29Cr–6Mo–0.09C decrease as compared with those observed in Co–29Cr–6Mo–0.02C. Moreover, the volume fraction of the γ phase slightly increased with C content. Within an extent of C addition that no carbide precipitation occurs, the carbon addition reduces the amounts of crystal defects such as stacking faults and twins, and ε martensites. In addition, tensile strength slightly increases with C content and ductility reaches a maximum at C content of 0.09%, though 0.2% proof strength shows no noticeable differences.

A novel family of bond coats designed to be in EQuilibrium with their nickel-base superalloy substrates has been developed. These coatings have hence been termed ‘EQ coatings’. The first step taken for EQ coating development was to examine the γ–γ′ tie-lines of several superalloys. In these superalloys, γ and γ′ are in equilibrium with each other, and elemental activities are thus equal in these two phases. With equal activities, there will be no chemical potential differences between the two phases, and there is thus no driving force for diffusion. Applying γ,γ′, or a combination of both as bond coat candidates will ensure that no inter-diffusion zone (IDZ) will form. This is desirable, as IDZ causes gross local mechanical property degradation.
In this paper, the γ′ volume fraction was varied from 0 to 100% at 25% intervals along the γ–γ′ tie-line of a nickel-base single-crystal alloy, TMS-82+. Cyclic and isothermal oxidation tests were conducted at 1100°C in ambient atmosphere. The resultant oxide structures, and the element concentration profiles from around the oxide/substrate interface, through the depletion zone, into the sound substrate, were analyzed by SEM/EDX.
All samples started with the same element activities; hence, at the onset of oxidation, all samples were expected to form the same oxide structure. However, experiments showed that the specimens formed vastly different oxide structures, and that γ′ had the best resistance against high temperature oxidation.

Gallium zinc oxynitride (Ga_0.93Zn_0.07)(N_0.90O_0.10) is a new type of photocatalyst that is capable of overall water splitting under visible light. The crystal structure of the (Ga_0.93Zn_0.07)(N_0.90O_0.10) was refined by Rietveld analyses of neutron powder diffraction data. The (Ga_0.93Zn_0.07)(N_0.90O_0.10) was confirmed to have a wurtzite-type structure (space group: P6₃mc). The present work demonstrates that oxygen substitutes for nitrogen in the crystal structure, and may be responsible for the desirable optical properties of (Ga_0.93Zn_0.07)(N_0.90O_0.10) as a photocatalyst for visible light-driven overall water splitting. The neutron scattering amplitude distribution through the maximum-entropy method (MEM) and MEM-based pattern fitting revealed that the crystal structure of the (Ga_0.93Zn_0.07)(N_0.90O_0.10) is free of interstitial sites and large disorder.

At the fractured tip of thin foil metals, heavy deformation takes place. At this heavily deformed region, vacancies play an important role. In Al–Pb alloy, lead precipitates are separated into small particles which are considered to be a result of enhanced diffusion by excess vacancies. The production source for these vacancies is considered to be internal nanocracks. In order to test this hypothesis, voids were searched in thin foil aluminum and gold, and void formation was confirmed in gold. It is considered that nanocracks not only become nuclei of voids but also contribute to the growth of voids by glide motion. The “Nanocrack fragment” model was proposed in order to account for the slide motion of nanocracks.

A Concurrent process for the synthesis and fabrication into rods of the machinable ceramic Ti₃SiC₂ by using a traveling-zone sintering method was investigated. Two different powder mixtures were prepared for the synthesis of Ti₃SiC₂. The first (TSC1) had the stoichiometric composition of Ti/Si/C = 3:1:2. In the second (TSC2), TiC was used instead of C to give a molar composition Ti/Si/TiC = 2:2:3. In the production of Ti₃SiC₂ rod from TSC1, there was a tendency for the cylindrical mold to become cracked during the sintering, because the synthesis of Ti₃SiC₂ from the simple mixture of Ti, Si and C occured by a tandem process and the primary exothermic reaction of Ti with C to form TiC caused a large thermal expansion of the material compact. On the other hand, Ti₃SiC₂ rod was successfully produced from the TSC2 mixture. Their density was elevated as increasing the sintering temperature and reducing the rate of movement of the stage, but employing too high temperature caused a reaction between the material powder and the mold, resulting in the product having unsatisfactory properties. The Ti₃SiC₂ rod produced contained varying amounts of TiC phase, the percentage of which showed a tendency to decrease under the same sintering conditions required to obtain a high density. We concluded that a well-densified, homogeneous Ti₃SiC₂ rod with high purity can be produced by the traveling-zone sintering method under the sintering conditions of a high temperature and a prolonged sintering time, if attention is paid to preventing reaction between the material compact and the mold.

Thermal barrier coatings (TBCs) with different levels of segmentation crack densities (D_s) were sprayed at different substrate temperatures (T_s). Thermal cycling resistance of the TBC specimen was examined. The segmented coating significantly improved the thermal cycling resistance as compared to the traditional non-segmented coating. Maximum thermal cycling lifetimes were achieved in the coating with a crack density level of 2.2 mm⁻¹. New segmentation cracks were hardly generated during thermal cycling testing. Spallation of segments within the segmented coating occurred, which is different from spallation of the whole coating from substrate in the case of traditional coating. Oxidation of bond coat and limited phase decomposition of YSZ topcoat were considered as not responsible for the failure of TBCs.

Characterizing of directional solidification mode of Fe–Cr–Ni alloys during welding was performed using intense synchrotron radiation probe. Consequently, the crystal growth in the rapid solidification process was revealed in detail and the peak profile was systematically analyzed in order to acquire the essential information for controlling the weld microstructure. Then, the crystallization timing of the primary and secondary phases was discussed. Furthermore, the possibility of the lattice rotation to commensurate (i) each dendrite and (ii) crystallites in the dendrites is suggested.

The wetting of a molten solder on metallic surfaces is a rather complex phenomenon. In addition to physical spreading due to surface tension reduction, there are interfacial metallurgical and flux chemical reactions with the metallic substrate surface. Substrate dissolution and intermetallic formation take place rapidly during soldering. Since lead-free soldering requires substantially higher soldering temperatures (around 250°C), the rates of intermetallic growth and substrate dissolution for lead-free solders are expected to be significantly greater than those for the current Sn–Pb eutectic solder. This study systematically investigates the metallurgy of the solid–liquid interface reactions and intermetallic growth kinetics for three lead-free solders: Sn–Ag eutectic (96.5%Sn–3.5%Ag), Sn–Cu eutectic (99.3%Sn–0.7%Cu) and Sn–Ag–Cu eutectic (Sn–3.8Ag–0.7Cu, SAC 387) with three metallic substrates: Cu, Ni, and Alloy 42 (42%Ni–52%Fe) over temperatures ranging from 225 to 280°C for reaction time from 10 s to 16 h. Wetting behavior of these three alloys on PCBs with OSP, immersion Sn, and Ni/Au finishes, was also examined from 220°C up to 260°C. A thorough understanding of lead-free solder/substrate interfacial reactions should give guidance to the optimum lead-free soldering processes and to the optimum lead-free coating thicknesses for component and PCB terminal finishes, as well as for under-chip metallurgical coatings for flip-chip and BGA applications.

Precursor phenomenon on the martensitic transformation was studied in Au_50.5Cd_49.5. For the precursor study, single variant of ζ₂′ martensite was produced and the reverse transformation process was utilized to avoid a superposition of several variants in diffraction experiments through the martensitic transformation, i.e. from parent to martensite phase. Atomic parameters in martensite state were refined with use of single crystal structure determination procedure by X-ray at various temperatures approaching the reverse transformation temperature. Atomic positional parameters of some atoms which are expected to have relatively large displacements from parent phase showed first-order feature.

Interdiffusion coefficients of the refractory elements in Ni–X–Y (X, Y=W, Re, Ru, Al) ternary systems, which are the fundamental systems of Ni-based superalloys, were estimated by a series of experiments using diffusion couples. The modified ternary Boltzmann–Matano method was employed for analyzing the experimental data. The cross interdiffusion coefficients were smaller than the main interdiffusion coefficients in all systems. Especially, the cross interdiffusion coefficient \\ ildeD_ReRu^Ni is much smaller by an order of magnitude than the main interdiffusion coefficient \\ ildeD_ReRe^Ni in Ni–Ru–Re system. This result indicates that the thermodynamical interaction parameter (Wagner’s interaction parameter) between Ru and Re is negligible, and implies that Ru does not affect the distribution behaviour of Re into γ and γ′ phases.

Change in nanocomposite structure in rapidly solidified Fe₈₆Nd₉B₅ alloy during electron irradiation was investigated. Nanocrystalline structure composed of α-Fe, Fe₃B, Nd₂Fe₁₄B and Nd₂Fe₂₃B₃ crystalline phases was formed by rapid solidification. Electron irradiation can introduce amorphization of intermetallic compounds and crystallization of an amorphous phase, resulting in the formation of a novel nanocomposite structure in which α-Fe and Nd₂Fe₁₄B nanocrystals are embedded in the amorphous matrix. The mechanism of nanocomposite structure formation was discussed based on the phase stability of amorphous and crystalline phases under electron irradiation.

The triangular phase in Ti–15V–3Cr–3Sn–3Al is observed after two-step aging. The three-dimensional shape of the phase is a triangular pyramid that is composed of three precipitates. The reason for the formation of the triangular shape is investigated by means of crystallographic analysis and high-resolution TEM observations. According to the HR-TEM observations, it is possible that the triangular phase has Potters OR with the matrix despite the existence of Burgers OR in an intragranular precipitate, as reported in previous studies. This suggests that in the alloy under consideration, the OR between the precipitate and the matrix is selectable in terms of lattice correspondence. As for the growth direction of the precipitate, an invariant line is investigated. Although the three precipitates have a common direction, which is [2\\bar1\\bar10]α⁄[111]β, their invariant lines are not parallel with each other, i.e., [\\bar447]α1, [\\bar744]α2, and [4\\bar74]α3. Therefore, the precipitates expand along each direction while growing and form a triangular shape.

In this study, high temperature tensile properties of high strength steels, POSTEN60 and POSTEN80, whose tensile strengths were 600 and 800 MPa respectively, were investigated through the elevated temperature tensile test. Residual stress measurements were also carried out to estimate the residual stress relaxation due to phase transformation (martensite transformation) in the process of cooling after welding. A finite element (FE) model which was able to include the volumetric changes due to the austenite → martensite phase transformation was developed on the basis of the experimental results. The three-dimensional thermal elastic-plastic FE analyses using the FE model were conducted to determine residual stresses in weldments of the high strength steels.
The results show that the extents of residual stress relaxation due to the austenite → martensite phase transformation in the process of cooling after welding are approximately 0.85 σ_x⁄σ_Y0 and 0.75 σ_x⁄σ_Y0 in the FZ and HAZ of POSTEN60 and POSTEN80, respectively. And residual stresses of weld line direction in the base metal (BM) which is adjacent to HAZ, therefore, do not undergo martensitic transformation increase (655MPa<870MPa) with increasing tensile strength of the high strength steels (POSTEN60 < POSTEN80).

The dynamic mechanical properties of high strength aluminum–scandium (Al–Sc) alloy are investigated using a compression split Hopkinson bar. Dynamic impact testing is carried out at nominal strain rates (abbreviated to strain rate hereafter) ranging from 1.2×10³ to 5.8×10³ s⁻¹ at room temperature. The effects of strain rate on the mechanical properties, microstructural evolution and fracture characteristics are investigated and the relationship between the mechanical properties of the alloy and its microstructure is explored. The measured strain–stress curves reveal that the dynamic mechanical behaviour of Al–Sc alloy is highly dependent on the strain rate. The flow stress, work hardening rate and strain rate sensitivity increase with increasing strain rate, but the fracture strain and activation volume decrease. The Zerilli–Armstrong fcc constitutive law is used to model the shear flow response of the Al–Sc alloy. A good agreement is found between the predicted and measured shear flow responses. The Al–Sc alloy specimens fracture as a result of shear band formation and crack propagation within the shear band. SEM observations indicate that the fracture features are dominated by a transgranular dimple-like structure. The density and depth of the dimples decrease with increasing strain rate. TEM microstructural observations reveal that the presence of Al₃Sc precipitated particles in the matrix and at the grain boundaries prevents dislocation motion and leads to a significant strengthening effect. An analysis of the dislocation substructure indicates that a higher strain rate increases the dislocation density, thereby reducing the size of the dislocation cells. The variations of the dislocation cell structure reflect different degrees of strain rate sensitivity and activation volume, and correlate well with the impact flow stress–strain response.

A stress corrosion cracking (SCC) test was carried out at room temperature in aqueous solutions containing both H₂SO₄ (0–5.5 kmol·m⁻³) and NaCl (0–4.5 kmol·m⁻³), in order to study the influences of both solutes on the corrosion type of SUS304 steel. The two solutes have synergistic influence on the corrosion type, that is, SCC and general corrosion occur within a specific concentration range and elsewhere, respectively. For a constant H₂SO₄ concentration the mass loss of corrosion shows a V-shape when it is plotted against NaCl concentration. On the other hand, maximum crack length of the SCC increases with increasing NaCl concentration up to a certain value, and then decreases. This gives a nearly inverse V-shape curve. In addition, the NaCl concentration ranges for the minimum mass loss and for the maximum crack length are almost the same. It was also confirmed that NaCl concentrations showing the minimum mass loss and the maximum crack length are inversely proportional to H₂SO₄ concentrations.

A green process has been successfully developed to mass-produce carbon nano-tubes (CNTs) using electric-arc-furnace (EAF) dusts as the catalyst. The CNTs were prepared by a thermal CVD process with the gas mixture acetylene and nitrogen flown directly on the EAF dust that was firstly treated by a reduction period. Preliminary experimental results illustrated that CNTs were easily synthesized in large quantity and in curly shapes. The characteristics of as-grown CNTs were evaluated by transmission electron microscopy and Raman spectrometry to be of good graphitic structure. This production method is extremely meaningful both environmentally and industry-wise.

The formation and ejection behavior of droplets created by a squeeze mode piezoelectric inkjet printing device using a double pulse voltage pattern are investigated in this study. Two types of fluid, de-ionized (DI) water and ethylene glycol, are used. The effects of operating frequency, positive voltage keeping time and pulse voltage magnitude on the volume and velocity of the droplets are discussed. The experimental results are consistent with the propagation theory of acoustic waves. The maximum allowable pulse frequencies in DI water and ethylene glycol are 2,000 and 22,700 Hz respectively. If the positive voltage keeping time equals the time required for the acoustic waves to propagate through the printhead, optimal ejection behavior is achieved. As the pulse voltage increases, both the velocity and volume of each droplet become larger.

A plastic deformation process and ratio study of p-type Bi_0.5Sb_1.5Te₃ was performed. The ingots were grown by the Bridgman method. Disks were cut from the ingots and deformed by either cold-pressing or by hot-pressing under pulse current heating. The plastic deformation ratio was controlled from 55 to 90%. The crystal structures of the deformed samples were identified by X-ray diffraction and pole figure analyses. The diffraction patterns indicate that the surfaces and bottoms of the samples were highly oriented in the hexagonal (00-l) plane. Thermoelectric properties change depending on not the plastic deformation ratio but the kind of plastic deformation process. The power factor for hot-press deformed samples exceeded those for the original ingots and cold-press deformed samples. The results suggest that the process of hot-press deformation enhances the thermoelectric properties of p-type Bi_0.5Sb_1.5Te₃.

Amorphous Al₂FeZr₆ alloy was prepared from elemental powders by mechanical alloying. The microstructure evolution was identified by X-ray diffraction. The thermal stability of amorphous Al₂FeZr₆ was determined by DTA. There are two overlapped exothermic peaks observed in curves of DTA. This indicates that two exothermic reactions in the procedure of crystallization of amorphous Al₂FeZr₆ alloy. The effective activation energies of crystallization were evaluated using Kissinger’s plot. The evaluated values of effective activation energy corresponding to the first and the second exothermic reactions are 266 and 299 kJ/mole respectively. The products of crystallization of amorphous Al₂FeZr₆ alloy are binary intermetallic compounds AlZr₂ and FeZr₂ instead of intermetallic compounds Al₂FeZr₆. It was explained by comparing their relative stabilities based on enthalpies of formation of intermetallic compounds.

The effects of electromagnetic vibration on macrosegregation in AZ80 magnesium alloy billets have been investigated experimentally. Comparing to conventional direct-chill casting, the enrichment for the alloying elements close to the billet surface is significantly reduced by the electromagnetic vibration. Increasing the stationary magnetic field, i.e., increasing the intensity of the electromagnetic vibration results in uniform distributions of the metallic elements in the billet. The distribution of impurity iron has the same tendency with alloying element manganese with and without the electromagnetic vibration. The uniformity in the concentration profile of iron is higher than that for the alloying elements in the billet and increases with increasing the stationary magnetic field of the system used for generation of electromagnetic vibration.

Five carbons with different graphitization degrees, which were heat-treated at temperatures of 1273 to 3273 K, were prepared. These carbons were bonded to nickel in a vacuum, using an RF-induction furnace, with joining temperatures of 1073 to 1273 K. On the basis of the results of these experiments, the effects of the graphitization degree on the solid-state bonding of carbon to nickel were examined. Carbon heat-treated at 1273 K remains amorphous, whereas most of the carbons heat-treated at 3273 K change into graphite because the graphitization degree increases with increasing heat treatment temperature. Strong bonding of amorphous carbon to nickel is not accomplished. The bending strength or joinability of carbon (with a graphitization degree lower than 0.28)/nickel joints depends on the joining temperature. Good bonding of carbon with a graphitization degree higher than 0.28 to nickel is achieved regardless of the joining temperature. The graphitization degree and thermal stress affect the joinability and bending strength of the joints.

The effect of melting of LiAlH₄ on its dehydrogenation properties was examined using Differential Scanning Calorimetry (DSC). LiAlH₄ samples purified in advance were examined on their hydrogen desorption behaviors in the various heating conditions in which some of them were melted and the others not. Some of the as-received samples were mechanically ground in an Ar atmosphere for a short time of period using a ball milling machine and then supplied to DSC measurements. The color of the sample after milling changes from gray-beige to grey, probably due to contamination of metal elements such as iron and chromium from hardened steel vessel and balls during grinding. The rapid hydrogen desorption was observed for the samples melted by heating, whereas the insignificant hydrogen desorption was observed for the ones which were not melted by heating, in spite that heating and cooling were repeated three times. The time from melting to decomposition of LiAlH₄ accompanied by hydrogen desorption was 90±30 s, independent of hydrogen desorption temperature. The samples milled in hardened steel vessel using a planetary-type ball milling machine exhibited about 2 K lower melting temperature and 15 K lower hydrogen desorption temperature than the as-purified samples. These changes can be considered to happen because contamination metal elements contributed to lowering a melting temperature and worked as a catalyst to decrease the activation energy for decomposition of liquefied LiAlH₄. These results indicate that metal elements such as iron and chromium certainly contribute to improve hydrogen desorption temperatures of alanates, as reported in many papers, but it is more important to lower their melting temperatures in order to improve their hydrogen desorption kinetics.

High-cycle fatigue tests were conducted to investigate the effects of temperature, stress ratio (R), specimen orientation, welding and specimen size on the fatigue behavior of type 316L stainless steel. The high-cycle fatigue test results indicated that the fatigue limits significantly decreased when the stress ratio (R) decreased. The corresponding fatigue limits were reduced to lower values when tests were conducted at 300°C, compared to those obtained at room temperature. The fatigue behavior and fatigue limits of standard and subsize specimens were observed to be consistent at both room temperature and 300°C. The constant life diagram was established from the S–N curves acquired. The fatigue limit strongly depended on the materials strength, which was a function of specimen orientation, test temperature, and welding processes. The dimension of the fatigue damaged area on a fracture surface increased as the stress ratio decreased. In the case of R=−1.0, the fatigue damaged region extended over the whole fracture surface. The subgrain boundaries after high-cycle fatigue tests were clearly demonstrated by their diffraction patterns, which were related to the dynamic recovery of multiple dislocations.

TiC/Ti and TiC/Ti–15Mo cermets were fabricated for the bearings of joint prostheses and were then evaluated in terms of their mechanical properties, such as density, hardness, bending strength and fracture toughness, as well as biocompatibility. The cermets were fabricated by spark plasma sintering. When the volume fraction of the metal phase was increased, the fracture toughness and the bending strength of the TiC/Ti and TiC/Ti–15Mo increased. The TiC/Ti and the TiC/Ti–15Mo cermets show high biocompatibility and corrosion resistance. These results indicate that TiC/Ti–15Mo cermets are suitable for use in the bearings of joint prostheses.

Hot Isostatic Pressing (HIP) is widely used in the casting industry to remove the internal porosity generated during the casting process. It combines higher pressure and temperature to produce materials and parts with substantially better properties than those by other methods. This results in improved strength, ductility and fatigue life of castings. The aim of this paper is to discuss the methods and to find a suitable soaking time of HIP for Inconel 718 superalloy castings. In this study, the HIP temperature was maintained at 1453 K, pressure was kept 175 MPa and three different soaking time are 2, 3 and 4 h. The experiment results show that HIP treatment at 1453 K under the pressure of 175 MPa for 4 h for Inconel 718 superalloy is the optimum condition. It can decrease the porosity of Inconel 718 superalloy castings. In this study, it can reduce porosity about 86% after HIP treatment. For the tension test at a fast strain rate (0.001 s⁻¹) that it increased the tensile strength by 31% at room temperature, 27% at 813 K, and 24% at 923 K. While at a very slow strain rate (0.0001 s⁻¹), it increased the tensile strength by 24% at room temperature and 20% at 813 K. For a 3-point bending test, it showed that the optimum soaking time of HIP procedure could enhance the bending strength by 38% at room temperature and 26% at 813 K.

In this study, the effect of RE content on the microstructure and creep properties of Mg–8Al–xRE (x=0, 1, 2 or 3 mass%) alloys were investigated. The microstructural analysis and phase characterizations of Mg–8Al alloy with 1–3 mass% RE (La-rich Mischmetal) additions were conducted. (i) The as-extruded Mg–8Al–xRE alloys consisted of an α-Mg matrix, β (Mg₁₇Al₁₂) and Al₁₁RE₃ compounds. (ii) Raising the extent of RE in the alloy also increases the amount and coarsening of the Al₁₁RE₃ compounds, but the amount of β phase diminishes and turns into the fine particles. The creep rupture life increment measured at 423 K is around 40–100 MPa, and the creep rupture life over 423 K is also prolonged. The marked improvement in high-temperature tensile creep properties is attributed to the fine rod-like Al₁₁RE₃ compound having high thermal stability in the alloys.

The creep behavior of the Ti–40Al–16Nb alloy and the effect of the minor addition of Sc are investigated by creep tests at 1073 K under constant load from 200 to 280 MPa. The creep curve of the alloy with high Nb contents does not exhibit a steady-state region, and the minor addition of Sc added to the alloy has no effect on minimum creep rate. The creep responses of the alloys with high Nb contents are strongly correlated with tertiary creep behavior. The effects of Sc addition are apparent on the properties of tertiary creep rate and rupture life. The tertiary creep rate of the Sc containing alloy is reduced and the creep fracture life is increased. Subgrain structures of dislocations are absent in the alloys with high Nb contents during secondary creep, and the deformation of creep converges mainly at the B2 phase. A stress exponent of 4.5 estimated indicates that the mechanism of controlling creep behavior is dislocation climb. The creep fracture of the alloys is dominated by cleavage fracture over the entire fracture surface. Sc₂O₃ particles are an effective obstacle to the propagation of cracks and the motion of dislocations.

The Cadmium Chloride flux increases the weld penetration evidently in the Alternating Current Tungsten inert gas (AC TIG) welding of magnesium alloy. In the present study, in order to investigate the effect of the CdCl₂ active flux on the weld shape and arc voltage, bead-on-plate specimens are made on AZ31B magnesium alloy pre-placed with CdCl₂ active flux by the AC TIG process. Weld pool cross-sections and the arc voltage are analyzed under different welding parameters, welding speed, weld current and arc length. The results showed that compared to the conventional AC-TIG, welding penetration and the weld depth/width with CdCl₂ flux are both two times greater than that of without flux under optimal parameters. The voltage decreases with decreasing of travel speeds and arc length decreasing. Besides, the phenomenon of arc trailing in the EN period and arc contraction in the EP period were observed in AC TIG welding of magnesium alloy with CdCl₂ flux. It found that the arc voltage increases with the increases of welding current, more energies are supplied for welding, resulting in the increases of arc voltage and weld penetration.

Effects of yttrium and erbium additions on glass-forming ability (GFA), thermal stability and mechanical properties of glassy Zr₅₅Al₁₀Ni₅Cu₃₀ alloy were studied. (Zr_0.55Al_0.10Ni_0.05Cu_0.30)_100−xRE_x (RE = Y, Er and x=0,0.5,1,2,3,5 at%) metallic glasses were formed by melt-spinning and copper mold casting. It was found that the addition of Y or Er greatly enhanced the glass-forming ability, thermal stability and mechanical properties of Zr₅₅Al₁₀Ni₅Cu₃₀ alloy. The alloys containing 1–3 at% Er can be cast into glassy rods with a diameter of 15 mm, which is larger than the critical diameter (10 mm) of the base alloy in the present work. With the addition of 1 at% Y, supercooled liquid region ΔT_x of the base alloy was extended from 89 to 102 K, compressive strength was increased from 1650 to 1800 MPa and plastic strain reached a value as high as 3.5%.