Influences of the solidification microstructure and the stress concentration factor on the fatigue characteristics were investigated for the JIS-AC4B alloy containing 6.79%Si, 2.93%Cu, 0.17%Mg and 0.59%Fe, and also for a iron free AC4B-type Al-Si-Cu-Mg alloy. Solidification microstructures of specimens consist of dendritic alpha, eutectic Si, Al2Cu and Mg2Si phases in both alloys, and furthermore, Fe compound appears among the dendrites in AC4B alloy. However, a few gas and shrinkage porosities appear in every specimen. The rotating bending fatigue tests were carried out on specimens with notches of 2, 1, 0.3 and 0.1 mm radius. Both of AC4B alloy and iron free AC4B type alloy specimens show the same fatigue sequence with increasing notch size larger than 1 mm, indicating that the gas and shrinkage porosities act as the origin of cracking and govern the fatigue characteristics. However, when the notch radius becomes smaller than 0.3 mm, that is, the stress concentration factor becomes larger than 2.4, AC4B alloy has higher fatigue strength than Al-Si-Cu-Mg alloy, which indicates the Fe-compounds retard the crack propagation.
The effects of Cu-containing pigments on degradation of Japanese paper have been investigated. A hand-coloured wood-block print of the late Edo era is used as a naturally aged specimen. To clarify the degradation mechanism, sheets of modern Japanese paper painted with powdered malachite are aged in an environment of 353.15 K(80°C), 65%RH. Pigments are examined with XRD. Degradation of the paper is examined with a three-dimensional fluorescence spectrometer. Cu content in the specimen is measured by ICP-AES and EDS. The Cu concentrations of the cross-sections of naturally aged specimen decrease with increasing depth. In addition, the Cu concentrations at the same depth of the artificially aged paper increase with aging. These results show that the Cu species diffuse from the right to the wrong side of the paper. Although the green pigment of wood-block print contains Cu species and As species, only the Cu species has been detected in the fiber of the degraded part of the paper. The degree of degradation of the accelerated sample painted with malachite becomes higher than that of the unpainted sample. Therefore Cu is the main species that participates in the degradation of paper. The fluorescence intensity of the papers painted with malachite decreased with increasing aging time. This result shows that diffused Cu ions make impurity levels in the band gap of cellulose.
Resistivities, internal stresses and thermal stability of strongly (111) oriented Cu thin films, which are the most promising interconnect materials in advanced ULSI devices, have been studied comparing with those of non-oriented Cu films. Their internal stresses within a film plain were measured by a conventional X-ray diffraction technique, while the strain distribution with depth by a grazing incidence X-ray scattering (GIXS) methods. The resistivity and X-ray diffraction measurements revealed that present strongly (111) oriented Cu films showed high thermal stability, compared with non-oriented Cu films. The internal stresses of non-oriented Cu films start to saturate above 200°C, whereas those of strongly oriented films tend to decrease at high temperatures. Both internal stress and hardness for the strongly (111) oriented Cu films increase with decrease of film thickness. It was found that the residual internal stresses of highly oriented Cu films increased almost linearly throughout the thickness up to the oxidized Si substrate. The change of the stress distribution with depth was measured as a function of annealing temperatures for strongly oriented Cu films. It was revealed that the change of internal stresses with depth was nearly the same as that of plain stresses with temperature.
Si3N4 ceramics are often used as sliding parts in severe environments because of their properties of high hardness, light weight and superior abrasion resistance. Oil lubricant is applied to minimize their friction and wear. In addition to or instead of oil lubricant, lipophilic and self-lubricating materials and processes are being explored. In this study, Fe3O4 and Mo were added to Si3N4 to enhance the lipophilic properties and the abrasion resistance, while retaining strength. As a result, after adding Fe3O4 or Mo, the hardness, bending strength and density of Si3N4 ceramics decreased, while the lipophilic properties and abrasion resistance were enhanced. The lipophilic properties and abrasion resistance of Si3N4 ceramics after adding Fe3O4 and Mo were enhanced by either porosity or Fe3O4 on the material surface. The contact angle of macro-oil droplets became lower after adding Fe3O4, while the contact angle of micro-oil droplets remained almost the same.
A technique for analyzing the relationship between the local plastic deformation and microstructures of a tempered martensitic steel was developed by means of an atomic force microscope (AFM). The local plastic deformation had been induced by applying plastic strain near the tensile yield point. AFM observations were done at the same locations before and after deformation. In 1500 MPa-class medium-carbon low-alloy steel (0.4 mass%C, 1 mass%Cr, and 0.2 mass%Mo) tempered at 673 K, blocks, cementite, and prior austenite (γ) grain boundaries were visualized by using the AFM observation technique for the electropolished surface of the tensile test specimen and its etched surface where prior γ grain boundaries had been selectively corroded. AFM observation of the surface of the tensile test specimen at the same locations before and after applying plastic strains of 0.2%, 0.4%, and 0.6% showed that local deformations were concentrated in relatively large blocks close to prior γ grain boundaries and that surface steps (5-39 nm in height) were generated.
Chemical reaction process(Ti+CrB→Cr+TiB) of isolated CrB particle in a Ti powder compact was investigated to find a proper sintering condition for producing TiB/Ti composites by reaction sintering. EPMA analysis revealed that the formation of TiB starts at 1223 K during heated with the rate of 0.17 K/s. The reaction proceeds topochemically with the movement of a reaction band from the particle surface to inside. The unreacted-core model was applied to the reaction of a CrB particle for the analyse the reaction rate of CrB particle. It was found that diffusion of Ti and Cr atoms in a TiB layer controls the whole reaction rate, and then the time of reaction finish at 1223 K was estimated as a function of initial CrB particle radius.