Owing to the quasiperiodic order, one independent term in the elasticity of quasicrystals (phonon–phason coupling) is characteristic of quasicrystals. It is not seen in conventional crystals and has continued to be a significant subject in the research field of quasicrystals. Recently, a novel method was applied to a Mackay-type Al–Pd–Mn icosahedral quasicrystal to prove the existence of phonon–phason coupling and to evaluate its strength based on the elasticity of quasicrystals. This study applied the method to a Tsai-type Ag–In–Yb icosahedral system to evaluate its phonon–phason coupling strength. We applied phonon strain to the quasicrystal at a temperature with active phason, and the induction of phason strain was successfully detected and evaluated using powder X-ray diffraction. We evaluated the phonon–phason coupling elastic constant of the Ag–In–Yb icosahedral quasicrystal to be 0.17 ± 0.04 GPa by quantitatively comparing the measured induced phason strain with our calculation results.

Dilute Mg–Zn–Y alloy with a mille-feuille structure (MFS) exhibits a mechanical strength comparable to Mg–Zn–Y alloy with long period stacking/ordered (LPSO) structure through kink deformation. In order to deepen understanding the thermal stability of the MFS-type Mg alloys, it is required to clarify the solute cluster structures composed of Zn and Y in solute enriched stacking faults (SESFs). In this study, electron energy-loss and energy dispersive X-ray spectroscopy based on scanning transmission electron microscopy (STEM-EELS/EDS) were conducted to investigate the electronic structure and composition of Zn and Y in the SESFs of the MFS-Mg alloy. Zn-L_2,3 spectra indicated that the valence charges of Zn in the dilute Mg alloy were different from that of the LPSO-type Mg–Zn–Y alloy. In addition, the intensity ratio of L₃/L₂ in Y-L_2,3 spectrum of the dilute MFS-Mg alloy was larger than that of the LPSO-Mg alloy, reflecting the electron occupancies of 4d_3/2 and 4d_5/2 orbitals of Y atoms were different from those of the LPSO-Mg alloys. STEM-EELS analysis of the SESF composition in the dilute MFS-Mg alloy indicated that the Zn/Y ratio should be lower than that of the LPSO-Mg alloy, which was confirmed also by STEM-EDS measurements. These results indicate that the cluster structure in the SESFs of the dilute MFS-Mg alloy should be different from the ideal Zn₆Y₈ cluster in the LPSO-type Mg–Zn–Y alloys.

The current study is an attempt made to synthesize nano B4C/Graphite reinforced Aluminum–Zinc–Magnesium alloy composites by altering the weight %age of B4C (2%, 4%, and 6%). SEM was used to examine the morphology and mechanical behaviour was done in accordance with ASTM standards (ASTM E8, E9, E23, and D790). The microstructure displays a nearly uniform dispersion of reinforcement particles in the matrix alloy, with no residual pore visible. From the XRD analysis it is identified that interfacial phases between the base material and ceramic strengthening particulates are identified as Al₃BC, AlB₁₂, Mg₂Si, SiAl₂ and it strive as strengthening mechanism of synthetic composites. The interfacial phases identified as Al₃BC, AlB₁₂, Mg₂Si, and SiAl₂, and serve as a strengthening mechanism for synthetic composites, according to XRD. When compared to the base material, intermixtures had higher hardness (28.07%), ultimate tensile strength (69.31%), compressive strength (18.58%). The flexural strength is improved (29.32%) due to higher dislocation density in the matrix and wider variations in the elastic modulus. The impact strength improved significantly (72%) due to a reduction in porosity and grain refinement.

β-type Au–Cu–Al alloy, which is known as Spangold, has been developed for biomedical applications due to its high biocompatibility and X-ray contrast. Despite that, the workability of the polycrystalline functional phases (i.e., L2₁ parent and martensite phases) is limited by grain boundary embrittlement. To enhance the mechanical properties of the martensite phase (M-phase) alloy, this study aims to introduce a ductile α-fcc phase with various fractions into the M-phase alloy by manipulating the alloy chemical composition. Fundamental analysis such as phase identifications, thermal analysis, microstructure observations, and tensile tests were performed. As a result, the dual-phase M+α-fcc alloys with varying α-fcc phase fractions were successfully practiced. Among all alloys, their lattice parameters and phase transformation temperatures showed merely slight alteration, suggesting that the chemical compositions of the functional M-phases are similar for all alloys. Hence, the variations in the mechanical properties mainly originate from the different α-fcc phase fractions. The tensile test results indicate that both the ultimate tensile strength and fracture strain are promoted as the α-fcc phase fraction increases. The 50Au–38Cu–12Al alloy with the highest α-fcc phase fraction performs the most optimized mechanical properties.

Changes in the microstructure and various properties of heavily cold-rolled Cu–Zn system alloys with small amounts of Ag were systematically investigated. While a typical heterogeneous nanostructure (HN) was evolved in all the alloys, the texture and ratio of the microstructural components developed were slightly varied depending on the added amount of Ag and Zn. The characteristic “eye”-shaped twin domains tended to evolve more significantly with increasing addition of these elements. Thermal stability of the HN structure appeared to be improved by Ag addition. This was due to grain-boundary segregation (GBS) of Ag, which enabled sufficient age hardening. The GBS in the HN structure also resulted in the improvement of electrical conductivity. In this way, all the alloys showed quite high-tensile strength over 900 MPa along transvers direction with superior electrical conductivity around or over 30% IACS. Maximum tensile strength achieved was 990 MPa with 34.5% IACS for Cu–30 mass%Zn–1 mass%Ag alloy.

This Paper was Originally Published in Japanese in J. Japan Inst. Copper 61 (2022) 1–8. Figure 1 and Table 3 were slightly modified from the original version.

Dies with high thermal conductivity (TC) can not only speed up heat transfer but also improve the production efficiency of parts and extend the life of the dies. Taking advantage of the high axial TC of carbon fibers (C_f), thermal channels are established in the composite. To protect C_f from being destroyed, C_f was electroless plated with Cu to form copper-plated C_f (C_f-Cu). Pores impede heat conduction, and the TC of the matrix is corrected by Bruggeman’s equation. C_f-Cu has high anisotropic, and its orientation can significantly affect the TC of iron-based composites. The mathematical equation between the orientation of C_f-Cu in the 3D model, the orientation of C_f-Cu on 2D cross-section, and the aspect ratio of an ellipse were obtained by C_f-Cu intersects with cross-section was determined by establishing a model of the orientation of C_f-Cu in 3D space. The simulated TC of the composite was calculated by 2D image analysis (finite element method). The effect of the orientation of C_f-Cu on the TC of composites with different C_f-Cu contents was investigated. When the volume fraction of C_f-Cu was 20%, the measured and simulated TC reached the maximum of 68.89 W m⁻¹ K⁻¹ and 71.02 W m⁻¹ K⁻¹, respectively. Before rolling, there is a significant difference between the simulated and measured TC. After rolling on the side surface of the rolling plane of the composite, both the simulated and measured TC on the rolling plane and its side surface show the same trend with the increasing of C_f-Cu content.

SPD-processed Al alloys have an ultra-fine-grained microstructure and extremely high strength. The strength of SPD-processed Al alloy exceeds the estimated it by the grain size using Hall-Petch relationship. SPD-processed Al has high dislocation density because the excess introduced strain remains in dynamically recrystallized grains. The excess dislocation may form the low angle grain boundary during dynamic recrystallization. Al–Mg alloy represents especially large strengthening by dislocation hardening after SPD not only smaller grain size than pure Al. This is because the stacking fault energy (SFE) of the alloy is lowered by Mg solute atom. The dislocation movement become suppressed during DRX in low SFE alloys. As a result, SPD-processed Al–Mg alloys have extremely fine-grained (∼0.25 µm) microstructure. SFE of the alloy may also affect the formation of low angle grain boundary and dislocation accumulation in the grain interior. The dislocation distributions could result the degree of extra-hardening. The distributions of dislocation and low angle grain boundary in ECAE processed Al–3 mass%Mg alloy were investigated by EBSD and XRD techniques. Annealing after ECAE for recovery the strain provides the relaxation of the strain hardening, in spite of the LAGB fraction remains static.

In this work, the hot processing maps of CF170 maraging stainless steel were generated by using flow stress data obtained from an isothermal compression experiment on the Gleeble-3800 hot compression simulator. The microstructure corresponding to the stable regions in the hot processing map was observed with an optical microscope. The results showed that the steel is susceptible to deformation temperature, strain, and strain rate, and the optimal hot working parameter is a strain rate range of 0.01∼0.1 s⁻¹ and a temperature range of 1350∼1373 K when the strain is 0.6. In addition, the texture evolution of prior austenite during hot compression was investigated based on reconstructing a parent grain by Electron Back-Scattered Diffraction. The results showed that twinning-induced dynamic recrystallization is another mechanism except for strain-induced dynamic recrystallization at a higher strain rate. Further, the deformed microstructure with a Cube texture (1 0 0) 〈0 1 0〉 will preferentially nucleate, and the increase in temperature makes the Cube texture (1 0 0) 〈0 1 0〉 change to the rotated Cube texture (1 0 0) 〈1 1 0〉, and the increase of strain rate inhibits the growth of recrystallized grains and weakens texture.

To improve the stretch flange deformation limit of ultrahigh-strength steels, a partial edge heating method was investigated. The effect of the strain gradient on the stretch flange deformation limit when a partial edge heating method was applied was investigated by the hole expansion test and FEM analysis. The stretch flange formability was improved by application of a partial edge heating method because of the recovery of the shearing microstructure and the reduction of the hardness difference of microstructure. It was found that the improvement of the deformation limit strain for the strain gradient with edge heating depends on the strain gradient region. In the low strain gradient region, the improvement margin of the deformation limit strain with edge heating was small. On the other hand, in the high strain gradient region, the deformation limit strain was markedly improved compared with that without heating. It was confirmed that the strain gradient in the direction perpendicular to the maximum principal strain could be used for the prediction of the deformation limit and also the determination of the stretch flange fracture by the FEM analysis of actual parts even under edge heating conditions.

This Paper was Originally Published in Japanese in J. JSTP 63 (2022) 59–64.

A numerical investigation of the kink strengthening mechanism in long-period stacking ordered magnesium alloy is presented. A higher-order gradient crystal plasticity model is introduced, and the reproducing kernel particle method is adopted for the numerical procedure. The specimen, including a kink band with several kink angles, which is defined as the angle between the inside and outside of the kink band, is considered. A simple shear analysis is conducted to evaluate the kink strengthening due to the kink band. The numerical results suggest two main origins of kink strengthening, namely, orientation and defect strengthening. The former is caused by the spatial distribution of the slip direction due to kink, and the latter is the strengthening induced by crystal defects around the kink boundary. The amplitude of kink strengthening depends on the kink angle, and an optimal kink angle, which maximizes the kink strengthening, might exist. The kink strengthening exhibits a Hall–Petch-like behavior, i.e., the correlation between the inverse of the square root of the kink band width and flow stress is almost linear.

To improve the corrosion resistance of Mg alloys, composite coatings of layered double hydroxide intercalated with carbonate (LDH-CO₃, hydrotalcite) particles and magnesium and aluminum hydroxide gel were formed on AZ31 Mg alloy by electrophoretic deposition (EPD) using the LDH-CO₃ suspension with Mg(NO₃)₂ and Al(NO₃)₃ in total of 1.25–125 mmol/L. Wet-dry cyclic corrosion tests were performed for the coated specimens after ultrasonication. LDH-CO₃ particle-rich layer and magnesium and aluminum hydroxide gel-rich layer almost alternately piled up to form a composite layer. The hydroxide gel adhered the particles together and to the substrate. At the bottom of the composite layer, flake-shape LDH-structured substance densely covered the substrate surface. The coverage and thickness of the composite layer increased from sub-micrometers to 30 µm with an increase of Mg and Al ion concentrations of the suspension. By ultrasonication, parts of the composite layer delaminated to expose the LDH-structured substance layer, while the coverage by the remaining composite layer increased with an increase of Mg and Al ion concentrations. The LDH-CO₃ particles and hydroxide gel composite coatings prevented corrosion initiation even in the areas where the LDH-structured substance layer was exposed.

WO₃-based photochromic composite films were fabricated using a translucent urethane resin and a peroxoisopolytungstic acid - methanol solution as raw materials. Moreover, and polyethylene glycol (PEG, molecular weight 1000) was added to the composite as a sensitizer. The WO₃ mean particle sizes in the obtained composite were 46–55 nm, which implies that by PEG addition caused a slight reduction in the particle size. Additionally, the coloring/bleaching rate and the transmittance module of the composite films were drastically increased by PEG addition. These improvements in photochromic properties were previously considered to be due to the effect of the particle size of WO₃ particles in the composite, but were mainly assumed the effect of photoinduced electron transfer, which is caused by the presence of PEG in the composites.

Copper–Chromium (Cu–Cr) pseudobinary alloys are promising materials for electrical application. Nevertheless, their fabrication remains limited by traditional techniques, which are not suitable for manufacturing homogeneous Cu–Cr alloys with uniformly distributed elements. Recently, semisolid-liquid manufacturing method has emerged as a promising technique route to fabricate Cu–Cr alloys. In this work, the laser-directed energy deposition (L-DED) as one of the laser additive manufacturing (LAM) technology, was successfully introduced for semisolid-liquid fabricating the homogeneous Cu–30 mass%Cr alloys. The obtained Cu–Cr alloys are constituted by fully melted Cu metallurgically combined with semisolid-liquid Cr. The close combination of Cu and Cr is benefit to improve the electrical conductivity of the alloy.

In recent years, casting molds made by sand-type additive manufacturing (AM) technology are increasingly being used to build prototypes and small-lot production casting products.

The development of this technology aiming at Mass-production applications in the future is progressing through the advancement of AM technologies and casting technologies.

The application to Mass production is expected to increase the potentials of the whole casting, by realizing more complicated internal structure, reducing product thickness and weight by improving the cavity precision, etc. One method which can meet such needs is the current AM technique using furan sand molds. It is performed on large molding machines and is based on the organic self-hardening process utilizing mainly furan binder.

This 3D AM sand mold using furan binder (hereafter referred to as “furan AM sand mold”) contains sulfurous acid gas generated by the thermal decomposition of the catalyst used or organic gases generated by the thermal decomposition of the cured binder during pouring. In some cases, it is necessary to take measures such as removal of the gases from the molds. Other issues also need to be improved in terms of the working environment and casting quality. Examples of practically applied 3D AM methods using inorganic binders are; ink jetting water to plaster or cement, or ink jetting water to coated sand (laminated sand coated with water glass).

However, various challenges are met with these methods, such as lack of high-speed large 3D printers and mold collapsibility is difficult after pouring.

Under these circumstances, we attempted to fill a furan AM sand mold with an inorganic binder consisting of phosphate and sulfate, and then sinter the sand mold in an atmosphere of 850°C so that the furan AM sand mold changes into inorganic mold. With this mechanism, strong bonded layers are formed by the formation of polyphosphoric acid by the high molecularization of phosphate and the fusion of sulfate, while the thermal decomposition of the cured furan binder is progressing.

As a result, this transforms the sand mold into a mold composed of only the inorganic binder. The resultant mold has been found to be sufficiently practical with almost no gas generation even under the condition of 1000°C. As for the problem of mold breakage, when water is added to the mold, the sulfate that forms the adhesion layer dissolves in the water, and this action allows the mold to be collapsed easily.

These results confirm that this mold has a balanced combination of good heat resistance, reduced harmful gases, and good mold collapsibility.

This Paper was Originally Published in Japanese in JFS 94 (2022) 181–186.

For the purpose of understanding the mechanism of grain refinement in cast metal by mechanical vibration, demonstration tests were conducted using an ammonium chloride solution. Ammonium chloride solution and molds with various shape were prepared for the water model experiment. In the case of an open mold, ammonium chloride crystals crystallized on the mold wall and grew toward the center of the mold without vibration. However, when vibration was applied, countless crystals generated at the upper side of the solution immediately after pouring. In the case of a full plugged mold, no wave and convection occurred in the solution even when vibration was added, and the behavior seen was similar to the case without vibration. When only convection occurred in the full plugged mold, crystals were found to move from the mold wall into the solution. When a weir was set in the riser, it helped prevent the generation of crystals on the mold wall of the riser from migrating to the specimen. When a mold with a weir was used for Al–2%Cu alloy, crystals in the specimen did not become refined as seen in the water model experiments.

These results demonstrate that a large amount of crystals are generated at the boundary between the surface of the molten metal and mold wall when molten metal is vibrated, and these fine crystals fill into the mold due to sedimentation or convection, thereby achieving grain refinement.

This Paper was Originally Published in Japanese in J. JFS 94 (2022) 62–68. Figure 4 and a reference number were corrected.

In this paper, the NiCoCrAlY coating prepared by laser cladding was modified by a high-current pulsed electron beam technique. Scanning electron microscopy and X-ray diffraction analysis were used to characterize the microstructure and composition of the coatings before and after irradiation, and then the changes in mechanical properties were revealed by comparing the hardness and friction properties of the two coatings. The results showed that the pulsed irradiation purified the coating surface, formed an evaporative recondensation layer and a plastic deformation layer, and produced a dense remelting layer with a thickness of 3–4 µm. The remelted layer led to an increase in the hardness of the irradiated coating and a decrease in the friction coefficient and wear. The pulsed irradiation effectively improved the mechanical properties of the coatings.

We grew ZnO films at different temperatures on glass substrates using thermal atomic layer deposition and investigated the current conduction mechanism of Pt/ZnO junctions. For ZnO samples grown at 46 and 96°C, the current flow through the ZnO layer was not possible at low temperatures such as 298 and 320 K because the ZnO layer under Schottky contacts were wholly depleted. However, the current conduction was observed with increasing the temperature, which was found to be dominated by the Schottky emission at 360 and 380 K and the Poole–Frenkel emission at 380 and 400 K. For ZnO sample grown at 141°C, the strong tunneling current could occur because very thin depletion region was formed because of the high carrier concentration of ZnO layer. The observed difference in the current conduction can provide a guidance how growth temperature of ZnO should be controlled to design the low-temperature grown ZnO based devices built on glass substrates.

Flux leakage in the rotor core bridges is a problem specific to interior permanent magnet motors and has been unsolved till date. It is widely known that if the bridges are partially non-magnetically improved with low magnetic polarization, the leakage flux will be smaller, and the rotor will have a higher magnetic flux. We proposed that the portion of the silicon steel sheets that becomes the bridge after pressing can be non-magnetized and laminated to fabricate the rotor core. Partially non-magnetic material with a polarization of almost zero was obtained by melting and mixing Ni–Cr alloy powder with the silicon steel sheets. This non-magnetic improvement treatment was applied to the bridge in the rotor core sheet, in which the non-magnetic area width was 1.45 mm, and the prototype rotor core was fabricated by laminating 60 rotor core sheets. Upon measurement, the rotor core showed approximately 35% higher magnetic flux than a conventional one, with the actual value nearly identical to that obtained from the magnetic field analysis.

We have evaluated local elastic properties at kink boundaries in dilute Mg–Zn–Y alloys based on scanning transmission electron microscopy (STEM), first-principles calculations, and geometrical phase analysis (GPA) by measuring atomic-scale strain fields around dislocation cores. STEM observations showed that dislocations constituting kink boundaries are extended into Shockley partial dislocations by accompanying solute-enriched stacking faults (SESF). Using GPA analysis, we found that strain distributions around the partial dislocation cores are asymmetric across the Mg matrix and the SESF, showing local elastic heterogeneity. Comparison with the calculated strain field model, it is indicated that the observed asymmetric strain profiles are essentially caused by a softening of the Mg matrix. This anomalous elastic softening can be interpreted as a change in strain energy of dislocations at the kink boundary, which may contribute to the unique deformation mechanism of kink in dilute Mg alloys.

Me-substituted W-type ferrites (AMe₂Fe₁₆O₂₇ with A = Sr, Ba, …, and Me = Co, Ni, Zn, Mg, …) can be obtained by standard solid state reaction but always contain secondary phases. Phase stability of SrMe₂Fe₁₆O₂₇ with Me = Co, Ni, Zn, and Mg sintered in various oxygen pressures of p_O2 = 0.2, 1, 10, and 387 atm were investigated using X-ray diffraction analysis, wavelength dispersive X-ray (WDX) analysis, and transmission electron microscopy (TEM). WDX analysis revealed that the W-type ferrites are described as SrMe_2−δFe_16+δO₂₇ because Fe³⁺ is partially reduced to Fe²⁺ even when synthesis is initiated from SrMe₂Fe₁₆O₂₇. Increasing the oxygen pressure suppresses the reduction of Fe³⁺ and the formation of the secondary phases. In addition, TEM analysis shows that the SrCo₂Fe₁₆O₂₇ single crystal is free of stacking faults. We conclude that the single-phase formation of the Me-substituted W-type ferrites is hampered by the discrepancy between initial and actual chemical composition caused by the appearance of Fe²⁺.

This Paper was Originally Published in Japanese in J. Jpn. Soc. Powder Powder Metallurgy 69 (2022) 455–460.

In order to prevent water pollution in closed waters such as inner bays and lakes, it is essential to establish a method to remove phosphorus and organic substances which cause water pollution. We have tried to give organic substances removal ability to a crystallization type phosphorus remover composed of gypsum and CaCO₃ by supporting useful microorganisms on the surface of the remover. In this study, the effects of types of microorganisms derived from activated sludge or culture solution on the water purification ability of the phosphorus remover supported with microorganisms were investigated. The porous phosphorus removal material was obtained from solidified gypsum containing NaCl by washing to dissolve the NaCl, silica coating and carbonating. The phosphorus removal material supported with micro-organisms by immersing in activated sludge showed high organic matter removal ability, and there was almost no change in phosphorus removal ability before and after the micro-organisms were supported. In contrast, when microorganisms were supported by immersing materials in culture solution, the phosphorus removal capacity was significantly lower than that before immersing in the culture solution. In addition, the removal capacity of organic substances was lower than that of the materials immersed in activated sludge. The decrease in phosphorus removal ability and low organic matter removal ability of the materials immersed in the culture solution are caused by the detachment of the silica coating layer and CaCO₃ on the surface of the phosphorus removal material. Therefore, activated sludge as the type of microorganisms is more effective than culture solution to prepare the water purification material which has both the phosphorus removal and organic substances removal capabilities.