The methodology of the CALPHAD approach including construction of the thermodynamic databases is reviewed. The thermodynamic description for multicomponent systems can be predicted on the basis of the thermodynamic data evaluated in the low order systems. Some examples of alloy design, for advanced materials such as Fe, Co and Ni-based and electronic materials, are shown. It is demonstrated that the CALPHAD approach is very useful for the development of new materials, and new powerful tool for computational materials design.
In order to examine the risk to resource security in Japan, this paper quantifies the outflow of base metals (iron, aluminum, copper, lead, and zinc) through export of end-of-life vehicles (ELVs) from Japan from 1988 to 2005 using the Trade Statistics of Japan and vehicles composition data. Estimates were also made for engine-related rare metals (manganese, nickel, chromium, and molybdenum) under statistical restrictions. This analysis shows that 45% of iron, 68% of aluminum, 27% of copper, 70% of lead, 25% of zinc, and 67% of rare metals in ELVs in Japan were not recycled and flowed out of the country, mostly in the form of used vehicle and parts. The destinations of these metals were mainly developing countries with rudimentary recycling technology. These results strongly indicate that many metal resources that could be utilized domestically from automobiles in Japan were instead scattered and lost overseas.
In our previous paper (J. Japan Inst. Metals 71(2007) 620-628), anomalous plastic deformation behavior accompanied by propagation of X-shaped strain localization was found in tensile test of SUS304 stainless steel at low strain rate less than 10-4 s-1. In this paper, the phenomenon was further investigated related to strain induced martensitic transformation (SIMT). Tensile tests for a plate specimen were conducted at room temperature at higher strain rates of 6.7×10-4 s-1 where no propagating strain localization was found and at lower strain rate of 6.1×10-5 s-1 where propagating strain localization was found. The volume fraction of martensite (VFM) that generated accompanied by propagation of plastic deformation was quantitatively estimated by X-ray diffraction. In the case of higher strain rate, the VFM was followeded as predicated by the kinetic model of Olson and Cohen. On the contrary, in the case of lower strain rate, the VFM increased almost linearly depending on the strain increase. It is clearly shown that the anomalous plastic deformation behavior found in the condition of low strain rate is caused by strengthening by SIMT.
Multidirectional warm caliber rolling process using oval grooves and square grooves was developed. Microstructure and mechanical properties obtained by this process in a low carbon steel were investigated. Ultrafine grains with high angle grain boundaries were generated in the center region in a material by just 2-pass oval-square caliber rolling. The region having ultrafine ferrite grains expanded along with rolling and almost all of region was occupied with ultrafine ferrite grains with high angle grain boundaries by 6-pass oval-square caliber rolling. Although apparent rolling reduction in this 6-pass oval-square process is 71%, large plastic strain larger than 3 can be introduced into materials due to the effect of multidirectional deformation. Comparing with square-square caliber rolling in which 21-pass is required to obtain fully ultrafine grained structure, oval-square caliber rolling is very efficient process to create ultrafine microstructure.
The characteristics and adhesive strength of a high Cr-Fe alloy plasma spray coating applied to the inner surface of cylindrical aluminum containers of 17 NAS battery cell used to leveling electrical power for 0.2 to 10 years were studied. The operating temperature of the batteries was 593 K±15 K, and the number of charge/discharge cycles per year was 300 on average. A Sulfide layers consisting mainly of Cr2S3 and Cr3S4 was formed on the surface of the high Cr-Fe alloy plasma spray coating, and the growth rate of sulfide layer was approximately 2 μm per year. Chromium sulfides also formed within the spray coating. Molten sulfur and Na2Sx which are positive electrode active materials, penetrated the coating through the interfaces of the sprayed particles. The deepest sulfides almost reached the wall surface of the aluminum container. The adhesive strength of high Cr-Fe alloy plasma spray coatings operating history of 3, 5, and 10 years, was in the range of 42-44 MPa, showing that the adhesive strength from the time of coating was maintained. After tensile testing, peeling only occurred at the middle region of the sprayed layer, indicating that the reason for the peeling of the coating was formation of chromium sulfide formed at the interfaces of the sprayed particles.
The dissipated amounts of rare metals (Au, Ag, B, Ba, Cr, In, Ni, Pb, Sb, Sn, Sr, Ta, Zn and Zr) in WEEE (Cathode Ray Tube TV, liquid-crystal display TV, plasma display panel TV, refrigerator, air conditioner, washing machine, microwave oven and cleaner) have been estimated. For the estimation, the number of WEEE was also estimated using the population balance model. The composition of the WEEE were examined by interviews and the measurement using energy dispersive X-ray diffractometer. The estimated amounts of the dissipation were evaluated by both the ratio of the dissipation to domestic demand and the weight amount of the dissipation by “total materials requirement” (TMR).
We report on the temperature dependence of the electrical resistivity and the Seebeck coefficient for the p-type Fe2(V1-x-yTixTay)Al alloys with compositions 0≤x≤0.10 and 0≤y≤0.10, in addition to the composition dependence of the thermal conductivity at room temperature. While Fe2VAl (x=0, y=0) exhibits a semiconductor-like behavior in the electrical resistivity, a slight doping of Ti and Ta causes a significant decrease in the resistivity at low temperature and a large enhancement in the Seebeck coefficient, reaching 90 μV/K for x=0.03 and y=0.10. The power factor is found to be substantially larger than that for the p-type Fe2(V1-xTix)Al alloys so far reported. Although the thermal conductivity for Fe2(V1-xTix)Al remains in the range of 24∼28 W/mK for 0≤x≤0.10, it decreases significantly with the Ta substitution, reaching 11∼12 W/mK for 0≤x≤0.10 and y=0.10. We conclude that doping of heavier atoms such as Ta reduces more effectively the lattice thermal conductivity.
Reduced activation ferritic/martensitic steels (RAFs) have a complex and fine lath martensitic structure consisting of several kinds of microstructural units, namely, lath, block, packet and prior austenite grain. However, it is by no means easy to distinguish the contributions of such units to the strengthening mechanism. In this study, the instrumented indentation test was carried out under a wide range of maximum indentation loads using the crept specimens of the RAFs, JLF-1, in order to clarify the contribution of each grain boundary to it's strength and degradation. Experimental results revealed that the block boundary was the most effective boundary and at least seven block grains were necessary for reflecting fully the effect of block boundary in the macroscopic hardness. In addition, it was also revealed that the decrease in matrix strength of block grain was predominant factor of the reduction in macroscopic hardness due to creep. The retardation of the decrease in block boundary strength restrained the significant reduction in macroscopic hardness in JLF-1.
Making the angle of a hair clipper blade edge acute improves its cutting ability but causes the edge to be susceptible to wear, resulting in decreased cutting service life. When we used an electric hair clipper with a movable blade having a 45° acute angle on its edge, the edge caused significant wear and thus shortened its cutting service life. In this research, we conducted experiments on the cutting service life by cutting artificial hairs and, according to the experiment results, verified that using a high-hardness blade would suppress the wear of the blade edge to increase the cutting service life. Furthermore, assuming that “degradation in blade sharpness is subject to the wear loss of the blade edge and the wear loss depends on the distance at which the blade edge slides on the cross section of the hair; in other words, on the total number of strands of hair cut and the hardness of the blade materials”, we estimated the cutting service life from the blade hardness, and obtained excellent agreement between the estimated and test results. When using blades having different initial edge angles and radii, the concept of this cutting service life estimation enables us to facilitate estimation of their cutting service life.
Austenitic stainless steel (SUS304) specimens were sputter-etched by using argon ions, and the formation process of protrusions on the surface was investigated by changing the sputter etching time. In addition, tensile and bending tests of the specimens were carried out to examine whether the delamination between the protrusion and matrix occurs or not. When the sputter etching time is 0.9 ks, fine conical protrusions with diameter smaller than 2 μm are formed relatively homogeneously on the surface. When the sputter etching time is 1.8 ks, they grow to more than 5 μm. In some cases, the holes and cracks are formed on the wall of protrusions. When the sputter etching time is 3.6 ks, the protrusions grow further and occupy whole surface, and finally they collapse to form ring-shaped protrusions. The tensile test of the specimens with conical protrusions shows that, even at a fracture strain of 0.53, the shape of the cones is almost maintained and the plastic deformation occurs mainly in the region around them without delamination of the cones. Also in the bending test, the similar behavior to the tensile test is observed. The tensile test of the specimen with ring-shaped protrusions also shows that the deformation does not largely occur in the protrusion but occurs in the region outside of them. The reasons for the above characteristics seem to be that the outer shell of the protrusion with higher Cr content is strong and the protrusion grows from interior of specimen keeping high coherency to matrix.
In this paper, recycling potential of copper was analyzed by using a dynamic material flow analysis and a material pinch analysis. In the dynamic material flow analysis, the amount of copper stock in use was quantified as the potential of secondary resources. The amount of stock in use of copper in Japan in 2005 was estimated as 160 kg/cap, which is similar to the result in North America. Next, we applied the material pinch analysis to the material flow of copper-based materials in Japan in 2005 to investigate the maximum recycling potential of copper products. The copper-based materials were classified into high-purity copper, brass, bronze and copper-nickel-zinc alloy so that the difference of their chemical compositions could be taken into account. We focused on the concentration of Zn, Sn, Fe, and Pb in copper-based material as indicators of the quality of the materials. Then, the quantity and quality of generated scrap were estimated. We assumed that the copper-based materials were collected without class-by-class separation from the end-of-life products, and the composition of scraps recovered from end-of-life products was calculated as a weighted average of the copper-based materials used in the products. The results of material pinch analysis showed that copper and copper alloy scraps were being recycled in almost optimum way in the current situations of separation and collection. Then, scenario analysis was performed by altering the separation technology, collecting rates, in order to quantify the reduction potential of virgin materials inputs in the material flow in Japan. It was predicted that the consumption of virgin materials could be reduced by half if the collecting rate was increased to 100% and each copper-based material was completely separated from end-of-life products.
A sliding wear test was conducted on a copper single crystal having (001) surface. Formation of fine grains was recognized locally near the worn surface. To find a criterion for generation of low-angle boundaries during the sliding wear, lattice rotation of the matrix and misorientation between adjoining points were measured using electron backscatter diffraction (EBSD) analysis. Particularly, we paid attention to the low-angle boundaries that were distant from the worn surface. Beneath the fine-grained area, orientation of the matrix continuously changed along the direction of depth. The continuous lattice rotation was understood from a concept of geometrically necessary (GN) dislocations whose density is proportional to a lattice rotation gradient ∂φ/∂x. Increase in the lattice rotation gradient that was measured from the EBSD analysis was recognized near the worn surface. However, at the subsurface layer where low-angle boundaries were generated, the lattice rotation gradient was no longer a function of depth, and was smaller than that of the region where the continuous lattice rotation occurred. Accordingly, the generation of the low-angle boundary could be caused by rearrangement of the dislocations that was induced by the sliding wear.
Phase transformation behaviors of the austenitic 301 stainless steel was studied under Fe+, Ti+ and Ar+ ions implantation at room temperature with 100, 200 and 300 keV up to fluence of 1×1021 ions/m2 and the microstructures were observed by means of transmission electron microscopy (TEM). The plane and cross-sectional observations of the implanted specimen showed that the induced-phases due to implantation from the γ matrix phase were identified as α′ martensite phases with the orientation relationship of (110)α//(111)γ and α//γ close to the Kurdjumov-Sachs (K-S). The ion implantation induced phases nucleated near the surface region and the depth position of the nucleation changed depending on the ion accelerating energy and ion species. It was also found that the induced marten sites phases nucleate under the influence of the stress distribution, which is introduced due to the concentration of implanted ions, especially due to the stress gradient caused by the corresponding concentration gradient.