Unidirectional orientation of the carbon fiber is essential in the fabrication of Cu-carbon fiber composites with high thermal conductivity, because the fiber exhibits its very high thermal conductivity only in the longitudinal direction. In this study, hot extrusion of a mixture of Cu powder and carbon fiber was applied to fabricate the unidirectionally orientated carbon fiber reinforced Cu-based composite and the effects of the volume fraction of carbon fiber on the thermal conductivity have been investigated. It has been demonstrated that hot extrusion of the Cu powder-carbon fiber mixture successfully align the fiber to orient along the extrusion direction, and consequently, the thermal conductivity in this direction increases with the volume fraction of carbon fiber. For the composite with more than 30 vol% carbon fiber, the application of ultrasonic vibration treatment to the powder-fiber mixture is effective for improving the homogeneity of the mixing and hence increasing the relative density and the thermal conductivity of the composite.

The effect of Ti addition on the oxidation resistance of high-purity 19%Cr ferritic stainless steels has been investigated during isothermal heat treatment at temperatures between 1073 K and 1273 K in air. The microstructures of scale and the scale/metal interface were investigated in detail by means of SEM-EBSD and FE-TEM together with μ-EDS.

The Ti addition increases the oxidation mass gains but simultaneously improves the critical temperature of the oxidation resistance. The formed scale is mainly Cr₂O₃ regardless of the addition of Ti but Ti addition increases the thickness of Cr₂O₃. Considerable reduction in the grain size of Cr₂O₃ by Ti addition was recognized, which was inferred to increase the oxidation mass gain due to the easy diffusion through the grain boundary. Furthermore, Ti is oxidized beneath the scale/metal interface as internal complex oxides, such as Al₂TiO₅ and Al₂Ti₇O₁₅because of the small amount of aluminum in the steels used. In a somewhat deeper region from the interface, θ-Al₂O₃ forms where Ti cannot be oxidized. The oxygen getter effect by Ti atoms is postulated to be responsible for improving the oxidation resistance.

In this study, TbFeCo thin films were prepared using DC-magnetron sputtering technique utilizing a conventional batch-type sputtering machine. The magnetic properties such as magnetic hysteresis loops and magneto-optical properties of the obtained films were measured. Furthermore, we precisely evaluated the “effective” amounts of elements, i.e., the amounts of constituents released by oxidation, in TbFeCo thin films. We also attempted to control the amounts of effective elements by changing the pre-sputtering condition before film preparation. This is because the pre-sputtering process greatly affected the effective amounts of elements in the prepared TbFeCo thin films, such that the magnetic properties were drastically different from sample to sample by altering the pre-sputtering condition. Insufficient pre-sputtering led to a relatively high oxygen content in the films in comparison with those prepared with sufficient pre-sputtering. Outstanding perpendicular magnetic anisotropy in the out-of-plane direction was observed in a film prepared after 60 min of pre-sputtering, which exhibited a coercivity (H_c⊥) value of 6.4 kOe from magnetic hysteresis measurements and 8.2 kOe from magneto-optical polar Kerr hysteresis measurements at an incident light of wavelength 700 nm. The saturation value of the polar Kerr rotation angle (θ_K) of this film was approximately 0.3°, which is comparable to the theoretically optimized value. Therefore, we demonstrated that high-quality TbFeCo films can be obtained with high reproducibility by using a simple batch-type sputtering machine and that there is a strong correlation between effective amounts of elements in TbFeCo thin films and their magnetic properties.

Fe-Cr-Al ferritic steel is one of candidate structure materials for next-generation nuclear and fusion reactor due to its good corrosion resistance by alumina layer formed on surface. While, the effect of aluminum on microstructural evolution under neutron irradiation seems not to be clear. In this study, in-situ electron irradiation experiment was carried out for Fe-12Cr-5Al and Fe-12Cr in order to investigate the difference of damage evolution between with and without aluminum. Electron irradiation to Fe-12Cr-5Al resulted in less number density and larger size of dislocation loops compared with that in Fe-12Cr. This suggested that aluminum in matrix would have a strong interaction with vacancy, leading to more interstitial flow into dislocation loops.

Many studies have been done so far about the occurrence of whiskers in Sn-plating. However, very few study has been conducted on the suppression method of whiskers, how to prevent occurrence of whiskers. It is empirically known that whiskers are suppressed by heat treatment. However, its suppression mechanism is still unknown.

In the present study, we investigated that how the amount and form of the intermetallic compounds, generated by heat treatment, change with an elapsed time. Then, effect of the amount and form of the intermetallic compounds on the occurrence of Sn whiskers was studied in detail. As a result, it was clarified that, in order to suppress the whiskers, the amount of the intermetallic compounds should be above 15%. The parameter, named as contour-length ratio, was introduced for expressing the uniformity of occurrence of the intermetallic compounds. This value should be above 1.2 to suppress the whiskers.

Polycrystalline Ti₂AlC alloys were prepared by spark plasma sintering of high purity elemental materials, and subsequently annealed at 1500℃ for 24 h. Nanoindentation behavior was studied on the grains with their surface normal directions parallel to 〈3362〉, 〈4481〉, 〈0001〉 and 〈1120〉. During loading of nanoindentation, pop-in events were found to occur for all the indentation directions. The critical loads of the first pop-in observed for the indentation directions parallel to 〈1120〉 and 〈0001〉 were higher than those for 〈3362〉 and 〈4481〉. Surface topography around the residual indents suggests that the basal slip dominates the plastic deformation upon indentation. These results suggest that the nucleation of the basal dislocation is a major barrier for the onset of plastic deformation underneath the indenter.

A precise characterization of fine precipitates is crucial because these precipitates control mechanical properties of steel materials. Different types of carbide precipitates appear in heat resistant Cr-Mo steels. Their identification requires characteristic X-ray and diffraction analysis because it is usually not possible to differentiate carbides from their size and morphology alone. Latest scanning electron microscopes that are equipped with multiple image detectors can give rich information on microstructures. Thus, in this paper, we study the conditions where secondary electron (SE) and/or backscattered electron image contrast will clarify the types of precipitates in a common 2.25Cr-1Mo steel. A mechanically polished bulk specimen was observed by systematically changing the SEM the acceleration voltages and working distances. We have found that low accelerating voltages with a short working distance enables differentiation of four types of carbides and AlN precipitate in this steel. A small penetration depth of primary electrons and selective acquisition of SE/BSE is the key to extracting material contrast. This technique will allow quantification of size, distribution and area fraction of each precipitate for a large area using a bulk specimen.

The dislocation structures in polycrystalline Fe-1 mass% Si after cyclic deformation were observed using high voltage electron microscopy in order to investigate the formation mechanism of the dislocation structures. Vein, wall, and cell structures were found in a deformed specimen. Detailed orientation and structure of the walls were analyzed. Burgers vectors of dislocations in the walls were a/2[111] and a/2[1  11]. A set of walls was arranged parallel to the (110) plane and it was found to be a part of labyrinth structure consisting of the (110) and (001) walls. It is suggested that the formation mechanism of the labyrinth structure in bcc metal is reasonably understood by extending the mechanisms in fcc metals.