Cu-Cu₂S-X alloys specimens solidified at a cooling rate of about 20 K/sec have been examined by SEM, and the key factors in controlling the morphology of sulfide inclusions have been studied from a thermodynamic viewpoint. In the specimens containing some crystalline inoculants, such as Al₂O₃ and ZnO produced by the deoxidation in the molten state, the solidification proceeds according to the stable phase diagram, forming dendritic or polyhedral Cu₂S by primary crystallization, and rod-like or stringy Cu₂S by the eutectic reaction. Without crystalline inoculants, droplets of Cu₂S are formed by the monotectic reaction, because the eutectic temperature in the stable Cu-Cu₂S system is estimated to be only 1 K higher than the monotectic temperature in the metastable system. These findings are in good accordance with those on MnS in Fe-MnS-X alloys.

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Uniaxial compression tests were conducted on the Ti-52 mol%Al intermetallic compound at the temperatures and strain rates ranging from 1173 to 1473 K and 4.0×10⁻⁵ to 5.0×10⁻³ s⁻¹, respectively. The mechanism of dynamic recrystallization of the compound was examined on the basis of texture analysis. A fiber texture was formed during dynamic recrystallization. The main component of the texture is given approximately by (032) (compression plane) irrespective of the deformation temperatures, strain rates and strains. The sharpness of the texture varies depending on strains and the peak stresses appearing in the true stress-true strain curves. Thus the texture formation should be attributed to the deformation process; the recrystallization process has an effect of changing the texture sharpness. One to one correspondence exists between the texture sharpness and the peak stresses when the texture sharpness is evaluated at true strains about −1.7. When the peak stress is low, the texture sharpens monotonously with increasing strain, whereas the textures at high peak stresses stop developing at the strains more than −1.0. These results suggest that the dynamic recrystallization proceeds by the mechanism succeeding to the formation of the texture by crystal slip at low peak stress conditions and the mechanism at high peak stress disturbs the texture development. The existence of the two different mechanisms which have been proposed by microstructural observation, namely strain induced grain boundary migration and the nucleation and growth mechanism, are elucidated by the texture analysis.

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Hot deformation of prior warm-worked 7075 aluminum alloy was studied by means of 2-step tensile testing at 798 K and at various strain rates, and metallographic observations. The Al alloy samples before hot deformation contained high density of dislocations and fine particles precipitated on them, which existed quite stably at 798 K. Strain rate dependence of flow stresses as well as flow curves changes clearly in the three regions of strain rate, \dotε; i. e. region I (lower \dotε), II (medium \dotε) and III (higher \dotε). Typical superplasticity taking place in region II leads to the total elongation to fracture of over 750% and the stress exponent of 1.7. Rapid work softening after a peak stress can result from the fine grains evolved in high density dislocation matrices and subsequent gradual work hardening from grain coarsening taking place at high strains. The average size of new grains can be expressed only by flow stresses developed during hot deformation. It is concluded that hot deformation behaviors of 7075 aluminum are affected sensitively by the change of grain structures and then hot deformation in region II can be controlled mainly by grain boundary sliding.

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The measurement of the three-dimensional shape of secondary recrystallized grains, and delamination, creep and tensile tests are made to clarify the optimum interlocking grain structure which fills such two opposing roles as the improvement of creep resistance and the prevention of grain boundary fracture in P/M tungsten fine wires. Some parameters characteristic of the degree of interlocking among grains are derived and reliably reflect a distinctive change in the contours of grains which are three-dimensionally constructed. The effect of grain configuration to suppress creep rates with an increase in the degree of interlocking is detected in the structure which has a small area of grain boundary. However, the increase in creep rate is confirmed in the structure which has a large area of grain boundary because of an additional interlocking. On the other hand, the tensile strength increases monotonically at room temperature as the grains are interlocked. It is therefore possible to decide the optimum structure which realizes both high tensile strength and high creep resistance at the same time.

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CeO₂-ZrO₂ powders with various ZrO₂ compositions, which were prepared by co-precipitation, were subjected to an evolved-oxygen gas-analysis. The samples were heated from 373 to 1323 K in Ar+H₂+H₂O gas mixtures. A closed-system oxygen analyzer developed by one of the authors was used to establish a constant ratio of H₂/H₂O and also detect the oxygen evolved from the samples. After the amount of evolved oxygen was recorded as a function of temperature, the samples were oxidized at 873 K in O₂ gas, then the 2nd deoxidation run continued by heating again from 373 K. The heating-deoxidation run was repeated three times, and the following conclusions were derived. (i): For CeO₂ powders, a peak on the J_O-T-t curve (1) was observed around 1073 K, and did not shift even on the 2nd and 3rd heating-deoxidation runs. (ii): On the 1st heating-deoxidation run, as the content of ZrO₂ was increased, a peak appeared around 873 K and became higher; the sub-catalyst at low temperatures was improved monotonously with the addition of ZrO₂. (iii): After the deoxidation and successive oxidation, the shapes of J_O-T-t curves (2) and (3) were essentially different from those of the 1st run. This came from the appearance of cubic φ′ phase, (Ce₂Zr₃O₁₀?), which had not been reported previously. (iv): By analyzing the J_O-T-t curves, two kinds of qualitative phase diagrams of the ZrO₂-CeO₂-CeO_1.5 ternary system were established. The evolution behavior of oxygen from ZrO₂-CeO₂ powders could be explained on the basis of the phase diagrams; it was proved that the oxygen evolution behavior of ZrO₂-CeO₂ powders at low temperatures as sub-catalyst is the best in the composition range of ZrO₂: 45∼65 mol% after the appearance of the φ′ phase.
It was inferred that oxygen vacancies played a part in the growth of φ′ phase, and therefore similar experiments were undertaken with the powders of X_Ce⁄X_Zr=2⁄3 doped with CaO. (v): When it was annealed at 1773 K for 50 h, almost a single phase of tetragonal φ was obtained. The φ phase turned to φ′ phase once deoxidized and successively oxidized. (vi): The structure of φ′ was approximated by a pyrochlore, though there was no oxygen vacancies; Zr and Ce atoms may take regular arrays. (vii): The grain of the powders became fine through the phase transitions: φ→pyrochlore→φ′, and the evolution rate of oxygen became fastest, along with a change in the phase diagram. (viii): Through the phase transitions, CeO₂-ZrO₂ powders with ZrO₂, 45∼65 mol% possess a regeneration property as automotive exhaust sub-catalysts, and may be durable at higher temperatures. (ix): Through the present investigation, it was demonstrated that the evolved-oxygen gas-analysis utilizing the closed-system oxygen analyzer with high sensitivity is highly effective for the evaluation of ternary phase diagram related to oxides and also the detection of plausible compounds.

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The effective valences Z^∗ and the non-dimensional number δ of carbon and nitrogen in γ-iron for the solid state electrotransport have been measured by the tangent method under the following conditions: electric field intensity=3.0-11.3 V·m⁻¹, temperature=1223-1323 K, initial carbon content=0.1-0.9 mass% and nitrogen content=0.025 mass%. The influences of these factors on Z^* and δ were examined, and the following results were obtained:
(i) At the electric field intensity below 5.0 Vm⁻¹, Z^∗ of carbon increased rapidly with decreasing electric field intensity, but δ kept constant. Above that value, Z^∗ of carbon was constant, and δ increased linearly with increasing electric field intensity.
(ii) Temperature did not influence Z^∗ and δ of carbon under the present experimental conditions.
(iii) Z^∗ and δ of carbon decreased gradually with increasing concentration of carbon.
(iv) Z^∗ of carbon and nitrogen increased slightly when both elements coexisted.

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The effect of prestraining on intergranular corrosion rate was studied to clarify the relationship between the preferential dissolution of grain boundary and the dislocation density for 423 K prestrained 304 stainless steel in H₂SO₄-NaCl solution.
The intergranular corrosion was not observed on solution treated specimen but was observed on prestrained specimens in 1.0 kmol/m³ H₂SO₄-0.2 kmol/m³ NaCl solution at −330 mV(vs S.C.E.). Localized intergranular corrosion was especially observed in 2.5% prestrained specimen. The amount of strain in the grain interior was 10.1% determined by an image analysis computer for 6.8% prestrained specimen. The intergranular corrosion rate and the dissolution rate for austenite were determined from the slopes of curves plotting the depth of intergranular corrosion or dissolution as a function of time. These rates were found to increase with increasing prestrain, that is, the dislocation density in the specimen. The dislocation density in the grain boundary for the prestrained specimen was predicted from the relationship between the dissolution rate of austenite and the dislocation density by using the intergranular corrosion rate for the grain interior. The dislocation density in the grain boundary was increased with increasing the amount of strain and was indicated higher values than the dislocation density in the grain interior. These changes of dislocation density in the grain boundary and the grain interior for the amount of strain were corresponded to the reported result of the dislocation density which was determined by using transmission electron microscopy.
It is considered that the intergranular corrosion is induced by the preferential dissolution due to the dislocation pile-ups to the grain boundary in this material.

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The effect of pre-oxidation on hot corrosion for Ni-20 mass%Cr-5 mass%Al alloy in molten Na₂SO₄-25 mass%NaCl at 1173 K has been examined by the measurement of corrosion loss, the electrochemical measurement and the analysis of surface oxide film formed on the alloy by pre-oxidation. Particular attention was given to the influence of pre-oxidation temperature. The pre-oxidation at 1173 and 1273 K led to a stop of the vigorous corrosion for the alloy in the molten salt, whereas the pre-oxidation at 1373 K did not lead to an inhibition of the corrosion. The anodic polarization curve measured for the alloy after the pre-oxidation, which stopped the vigorous corrosion of the alloy, showed the spontaneous passivation behavior, while that measured for the alloy without the pre-oxidation showed a large current peak due to the active dissolution reaction. This suggests that the pre-oxidation treatment inhibits the electrochemical corrosion reaction for the alloy. Such an inhibition effect on the corrosion was investigated by the analysis of surface oxide film formed by the pre-oxidation. The formation of oxide films consisting mainly of Cr₂O₃ was observed for the alloy after the pre-oxidation at 1173 and 1273 K, while that consisting mainly of Al₂O₃ was observed for the alloy after the pre-oxidation at 1373 K. Consequently, it was found that the difference in inhibition effect on the hot corrosion due to the pre-oxidation temperature resulted from a difference in the kind of oxide constituting the oxide film formed by the pre-oxidation.

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Dependence of the light emission yields on discharge voltage and current in glow discharge spectrometry (GDS) were discussed. The emission yield varies inversely to voltage and increases linealy with current. This dependence on voltage and current is not affected by the causes to alter the voltage or the current: argon gas pressure or element composition of specimen. The current/voltage dependence of the emission yields implies that the influence of voltage change on the emission yield is larger than that of current change. For this reason, the measurements on the constant voltage mode should be employed for quantitative analysis by GDS. However, correction of emission yields using its voltage dependence reduces the standard deviations of analytical values in the case of the constant current mode.

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It has been considered that glass to metal joining is realized by the effects of mechanical anchoring and chemical composition gradient. These effects contribute to prevent glass peeling off caused by the difference in thermal expansion coefficient between glass and metal coupled. In order to clarify these ideas, the interfacial microstructures were studied with a high resolution analytical electron microscope. From the experimental results we found that the interfacial zone was composed of a very complex shape acting as the anchoring effect, and the transitional layer of ∼20 nm in thickness between glass and steel substrate was formed in the layer subjected to the chemical effect. The glass region in the transitional layer with the gradient of the iron component into the glass matrix was kept under the compressive displacement of ∼10%.

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Fe-Cu super-saturated solid solution powders were prepared by mechanical alloying of the elemental Fe and Cu powders, and the sintering behavior of the mechanically alloyed powders was investigated in association with the separation behavior of the liquid Cu phase. The chemical compositions of the mechanically alloyed powders were 10∼33 mass%Cu. The powders obtained were very hard in the as-milled state, so that they were subjected to a softening treatment of 1173 K-0.6 ks, and then compacted to test pieces using metallic die. Sintering of the powder compacts was performed at 1373 K which is just above the melting point of copper.
During the ball-milling of Fe-Cu powder mixtures, an extremely large energy is stored within powder particles and single-phase bcc solid solutions are synthesized for the alloys of up to 25 mass%Cu. The large stored energy leads to grain-refining of the (α-Fe+ε-Cu) two-phase structure formed in subsequent softening treatment. In the early stage of sintering, the liquid Cu phase oozes onto the grain boundaries to separate fine γ-Fe grains, and the rearrangement of separated γ-Fe grains results in densification of Fe-Cu powder compacts. For example, an Fe-25 mass%Cu powder compact, in which the liquid Cu phase oozed homogeneously, was densified to 98% in relative density only by sintering treatment, without singnificant coarsening of the microstructure. The sintered material has fine α-Fe grains of less than 20 μm even after sintering of 1373 K-3.6 ks.

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Recently, electrolytic capacitor of tantalum have been demanded to be smaller in size and higher in performance. But there is few reports about sintering of tantalum. Then, in this work, the tantalum was sintered by hot isostatic pressing (HIP ping) without capsule, so-called a capsule-free HIP (CFHIP), under the high pressure of argon gas and was sintered also in vacuum furnace at 1523 and 1623 K for 1 h. The volume shrinkage with sintering was measured and the properties of pore of the sintered tantalum were measured by a mercury pressure porosimeter, too. The surface was observed by SEM and capacitance was measured. The sintering behavior and characteristics of pores of the porous tantalum compact sintered under CFHIP and in vacuum were investigated. The results obtained are as follows. The shrinkage of volume under both sintering conditions became larger with the higher sintering temperature. The volume shrinkage of tantalum sintered under CFHIP was samller than by sintering in vaccum. From the SEM image, it was obviously clear that tantalum powder was lumped larger by sintering in vaccum as compared with under CFHIP. The pore of these sintered compacts, in this experimental region, was open. The mean diameter of pores of the sintered compacts with CFHIP was smaller as compared with those sintered in vaccum and the specific surface area of the sintered compact with CFHIP was larger than that sintered in vacuum. The capacitance of the sintered compact increased with increase of its specific surface area and the capacitance of the specimen treated at 1623 K was larger.

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The interface microstructure and peculiar wetting phenomena observed in the α-SiC single crystal and liquid Cu reaction system has been examined. α-SiC decomposes into Si and C in contact with Cu liquid at 1100°C. Si dissolves in Cu liquid and no silicide was observed. C forms fine grains of glassy carbon. The reaction layer is deeply formed into the α-SiC side. A specific orientation relationship was found between α-SiC and Cu as following.
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\ oindentThe hexagonal spreading of Cu on α-SiC single crystal is caused by fine hexagonal pits formed on the surface of α-SiC.

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Sn-Ag eutectic solder has been examined as one of the candidates of the lead-free solder comparing with Sn-Pb eutectic solder and pure Sn. All interfaces have Cu₃Sn and Cu₆Sn₅ reaction layers. Cu₆Sn₅ grows into solders like “peninsula”. Kirkendall voids are formed at the Sn/Cu and Sn-Pb/Cu interfaces but not at the Sn-Ag/Cu interface. The tensile strength of the Sn-Ag/Cu joint is higher than those of the Sn/Cu and Sn-Pb/Cu joints. Fracture takes place along the Cu₆Sn₅ layer and the linkage of preceding microcracks at the bottom of Cu₆Sn₅ peninsulas is responsible for the fracture. Sn-Ag solder has fine dispersion structure of Ag₃Sn particles forming subgrains. Ag₃Sn particles have a specific orientation relationship with the Sn matrix as shown below.
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The reactivity between titanium di-oxide and aluminum in aluminum alloy composites dispersed with rutile-type titania has been investigated by the thermal analysis and the morphological observation. The reaction of practical grade TiO₂/Al composites has proceeded by the heat-treatment at the solidus temperature of aluminum alloys, while the reaction has never occurred at the solidus temperature in the case of high purity TiO₂/Al composites. The difference of the reactivities between these composites at the solidus temperature is attributed to the effect of a small amount of Na which was one of the impurity elements in the practical grade TiO₂. Furthermore, the high purity TiO₂/Al composites doped with Na have shown an exothermic reaction at the solidus temperature. The difference between the morphology of Na doped TiO₂/Al composites heat-treated at the solidus temperature and that of high purity TiO₂/Al composites heat-treated at the liquidus temperature, suggests that the reaction mechanism between these cases is different. The apparent activation energy of the reaction at the solidus temperature has been estimated as 255.7 kJ/mol by calculating from the measurement of DSC. The present results suggest the possibility to control the reaction between inorganic materials and metals in the composites by the addition of small amount of an impurity element for the novel processing of composite materials.

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The compound semiconductor crystals of CuInSe₂ were grown by the traveling heater method using pure In or Cu-40 at%In alloy as the solvents. The EPMA composition mapping was stoichimetric and homogeneous throughout the crystals. By using the pure In and Cu-In alloy solvents, the n- and p-type conductions resulted, respectively. The carrier concentration and mobility were 4×10²²∼1×10²³ m⁻³ and 3×10⁻²∼9×10⁻² m² V⁻¹ s⁻¹ for the n-type, while in the order of magnitude of 10²¹ m⁻³ and 10⁻³ m² V⁻¹ s⁻¹ for the p-type at 300 K, respectively. The photoluminescence spectra indicated the characteristic features depending upon the solvents. In the case of the n-type, the origins of the emissions were identified as free exciton and V_Se, while those were free exciton, Cu_In and V_Se in the p-type. The emission intensity measurements indicated that the excitonic emission was predominant in the crystals grown by THM and increased from bottom to top end in the crystals, where lattice defects almost remain constant. The results for the crystals grown by THM showed a clear contrast to that obtained from that by the Bridgman method in which the nonradiative recombination centers were predominant. The laser Raman spectra were almost similar among the CuInSe₂ bulk crystals grown by THM and the Bridgman method.

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We have developed a device for in-situ measurement of the amount of photo-electron emission (PEE) at high temperature. The relation between the amount of PEE and the initial oxidation behavior of pure iron, pure nickel and SUS04 stainless steel was studied. The amount of PEE increased rapidly and then decreased gradually with the increase of temperature on the environment where oxidation occurred. The visible oxidation occurred after the peak of PEE. The amount of PEE decreased with oxidation time at high temperature, while it increased with time at low temperature and became more than 4 times that at high temperature in the case of iron. The amount of PEE was independent of the temperature, because the amount of PEE did not change in such a metal as gold that is not oxidized. The difference in the amount of PEE with temperature is considered to be assigned to the difference in adsorption behavior of oxygen and water molecule.

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