Silicon (Si) has attracted considerable interest as a negative electrode material for next-generation lithium (Li)–ion batteries because of its high capacity density. In this study, ex situ electron microscopy was applied to observe Si negative electrodes under different charge states within an actual battery structure to reveal the Li intrusion direction and the effects of Li concentration on the electrode structure. All of the processes from disassembly of the charged battery and preparation of specimens for use in electron microscopy observation to specimen transport to the electron microscopes were performed under non-atmospheric exposure conditions. The orientation of the single-crystal Si powder in the charged state was observed by electron backscatter diffraction, indicating that lithiation occurred preferentially along the (110) plane of Si. The initial stage of amorphization was observed by high-angle annular dark field-scanning transmission electron microscopy, demonstrating that the Li atoms occupied the tetrahedral sites of Si crystals, and that the crystal structure was destroyed via the severing of Si–Si bonds between the {111} planes. During the charge reaction, Li occupied the tetrahedral sites via intrusion along the 〈110〉 direction of Si, and amorphization proceeded as the Li concentration increased. Thus, the amorphous region grew preferentially in the 〈110〉 direction of Si.

Five Ir–Rh–Ru–W–Mo alloys selected based on alloy design with valence electron concentration (VEC) were examined for their formation of single, dual, and triple phases of bcc, fcc, and hcp structures. These structures were predicted with Thermo-Calc 2019a and the TCHEA3 database on a cross-sectional phase diagram along a composition line: Ir_{0.415254(100−2x)}Rh_{0.415254(100−2x)}Ru_{0.169492(100−2x)}W_xMo_x (x: 0–50 at%). At T = 2100 K, four types of phases were predicted: (1) a single bcc, fcc, and hcp phase, respectively, at x = 35 (Alloy A, VEC = 6.849), 15 (Alloy C, VEC = 7.981), and 5 (Alloy E, VEC = 8.574); (2) a mixture of bcc+hcp and hcp+fcc at x = 24 (Alloy B, VEC = 7.472) and 8 (Alloy D, VEC = 8.378), respectively; (3) a triple mixture of bcc+hcp+fcc; and (4) a mixture of bcc+fcc in Alloys A–E at low temperature. Experiments at 2100 K revealed that Alloys C–E tended to exhibit better reproducibility and that Alloy E can be regarded as a new refractory high-entropy alloy (HEA) with fcc structure. Alloy C annealed at T = 1273 K for 200 h maintained a single-hcp structure. The non-appearance of thermodynamically stable phases at low temperature in the Ir–Rh–Ru–W–Mo system was analogically explained as slow diffusion. The VEC analysis for HEAs with hcp structures was extended by including the range of 7.5 ≤ VEC ≤ 8.4 for alloys consisting of 4d and 5d transition metals annealed near their solidus temperature. The Ir–Rh–Ru–W–Mo system was significant in providing all possible simple solid solutions of bcc, hcp, and fcc phases.

High-entropy alloys (HEAs) with a single hexagonal close-packed (hcp) structure were found in Ir₂₆Mo₂₀Rh_22.5Ru₂₀W_11.5 and Ir_25.5Mo₂₀Rh₂₀Ru₂₅W_9.5 alloys annealed at 2373 K for 1 h. These HEAs were designed based on a sandwich strategy for valence electron concentration (VEC) of the constituent elements and by referring to their crystallographic structures in the periodic chart. The initial component and composition of these alloys were determined by considering exact and near equiatomic sub binary phase diagrams, followed by optimizing the composition by Thermo-Calc with the TCHEA3 database for HEAs as well as the SSOL5 database for solid solutions. The X-ray diffraction analysis, scanning electron microscopy observation, and energy-dispersive X-ray spectroscopy analysis revealed that the Ir₂₆Mo₂₀Rh_22.5Ru₂₀W_11.5 and Ir_25.5Mo₂₀Rh₂₀Ru₂₅W_9.5 alloys annealed at 2373 K for 1 h were formed in an hcp single phase. The formation of the hcp structure was principally evaluated by the VEC values of 7.855 and 7.865 for Ir₂₆Mo₂₀Rh_22.5Ru₂₀W_11.5 and Ir_25.5Mo₂₀Rh₂₀Ru₂₅W_9.5 alloys, respectively, such that these values were close to VEC = 8 for pure elements Ru and Os with an hcp structure. It is considered that Ru is a strong hcp-forming element under this strategy because the other pure constituent elements have different crystallographic structures. The formation of Ir₂₆Mo₂₀Rh_22.5Ru₂₀W_11.5 and Ir_25.5Mo₂₀Rh₂₀Ru₂₅W_9.5 HEAs with an hcp structure is unique because these alloys, which consist of only transition metals, can be produced without applying high pressure, similar to a CrMnFeCoNi HEA with an hcp structure.

A computational study for the modeling of lath martensitic steels, considering morphological and crystallographic features, is presented. A two-dimensional multi-scale tessellation is proposed to generate idealized microstructures with several scales of heterogeneities. The proposed approach is applied to lath martensite where prior austenite grain, packet and block boundaries are explicitly considered as well as their crystallographic relationships. The role of the different sources of heterogeneity on fatigue crack initiation is then investigated by finite element simulations including a single-crystal plasticity model. A fatigue criterion based on the Tanaka-Mura model is evaluated. The results indicate that block morphology and their orientation relationship significantly affects the strain distribution and the predicted location of crack initiation. In this regard, the effective critical size for crack initiation in low-carbon steels appears to be the block size as the Tanaka-Mura model mainly predicts cracks initiation along the block direction.

The grain boundary region of NdFeB sintered magnets were modified by reduction-grain boundary diffusion (r-GBD) process using Heavy Rare-Earths (HRE = Dy or Tb) metal which generated via reduction of HRE compounds such as oxide or fluoride with Ca metal vapor. After modification, magnetic properties were measured accurately by superconducting magnet-based vibrating sample magnetometer (SCM-VSM). The coercivity of DyF₃ and TbF₃ treated magnets with the assistance of reduction by Ca metal vapor (H_cJ = 1451 kA/m and 1778 kA/m, respectively) were effectively enhanced compared to untreated magnets (H_cJ = 1003 kA/m) without severe decreasing of remanence value. The resultant coercivity was higher than that of the magnets modified with DyF₃ (H_cJ = 1319 kA/m) and TbF₃ (H_cJ = 1580 kA/m) without using any reducing agent such as Ca metal vapor.

The high temperature deformation and microstructure evolution of Ni–Co base superalloy TMW-4M3 during the isothermal forging process were studied. A uniform compression test of TMW-4M3 where both the strain rate and compression temperature were controlled showed dynamic recrystallization flow stress. The peak stress and steady stress of the deformation resistance curve were characterized with the Zener-Hollomon parameter. The average grain size after dynamic recrystallization was also correlated with the Zener-Hollomon parameter, but this relationship changed with compression temperature. We found that this temperature dependency was related to the pinning effect of the γ′ precipitates in the γ matrix and proposed a new prediction model for dynamic recrystallization grain size considering not only the Zener-Hollomon parameter but also the volume fraction of the γ′ precipitates. This enables us to calculate the average grain size after isothermal forging within an error of 12%.

In this work, acoustic emission (AE) monitoring was correlated with in-situ optical microscopy observation and electron backscatter diffraction (EBSD) measurements to investigate the evolution of a single stress corrosion crack in SUS420J2 stainless steel subjected to chloride droplet corrosion. A single dominant crack evolution was observed to transition from a slow initiation of active path corrosion-dominant cracking to a rapid propagation of hydrogen-assisted cracking. The initiation-to-propagation was concomitant with a significant increase in the number of AE events. In addition, a cluster analysis of the AE features including traditional waveform parameters and fast Fourier transform (FFT)-derived frequency components was performed using k-means algorithms. Two AE clusters with different frequency levels were extracted. Correlated with the EBSD-derived kernel average misorientation (KAM) map of crack path, low-frequency AE cluster was found to correspond with the location of plastic deformation in the propagation region. High-frequency AE cluster is supposed to be from the cracking process. The correlation between AE feature and SCC progression is expected to provide an AE signals-based in-situ insight into the SCC monitoring.

The effects of elapsed time following gas metal arc welding (GMAW) on the static strength of lap fillet-welded joints were investigated using a static tensile test. It was observed that the static joint strength did not exhibit a time dependency for cases where the fracture was located in each base metal or the softened heat affected zone (HAZ). In addition, the static joint strength was not observed to have a time dependency for cases where a wire with low-hardness weld metal was used and where the fracture was located in the weld metal. However, the static joint strength was low immediately after welding, and increased over time when a wire with high-hardness weld metal was used. It was found that diffusible hydrogen that entered the weld metal during arc welding and was emitted over time was the cause of the time dependency of joint strength. High-hardness weld metal was sensitive to diffusible hydrogen; therefore, time dependency was observed only when wires with high-hardness weld metal were used and the fracture positions were located in the weld metal during tensile tests. In addition, a correlation between the storage temperature following welding and the static strength or diffusible hydrogen content of welded parts was found: the higher the storage temperature, the earlier the joint strength increases, and the earlier the diffusible hydrogen decreases.

This study tries to reveal the mechanism of forming fine and dense oxide particles in oxide dispersion strengthened (ODS) ferritic steel during heat treatment after mechanical alloying (MA). The MAed powders with and without titanium are set to the heat treatment from 873 K to 1423 K and analyzed by small angle X-ray scattering and X-ray diffraction using synchrotron radiation, transmission electron microscopy, and 3D atom probe. Yttrium and oxygen are segregated along the grain-boundaries induced by MA and form clusters after 873 K annealing. Fine oxide particles are densely formed before primary-recrystallization of the nano-sized grains induced during MA, at 973 K. The formation of cubic-Y₂O₃ and Y₂Ti₂O₇ are observed at 1273 K and above, where the size reduction of the oxide particles by Ti-addition is clearly shown.

The corrosion potential and corrosion rate of steel under wet/dry transitions were investigated using the Kelvin probe/pressure difference measurement system in order to elucidate the effect of Sn on the corrosion of steel covered by a thin electrolyte film in wet/dry environments containing chloride ions (Cl⁻). The corrosion rate in the case of an electrolyte containing Cl⁻ during the drying stage was higher than that in the case of an electrolyte containing sulfate ions (SO₄²⁻). Cl⁻ accelerate the hydrolysis of Fe³⁺ and lead to the acidification of the anode site in the thin electrolyte film, while also contributing to corrosion during the drying stage. The Sn-bearing steel showed a lower corrosion rate during the drying stage than that of the mild steel. This was because the Sn ions from the steel can exist stably in the acidic thin electrolyte film and inhibit the anodic reaction during the drying stage. Thus, the superior corrosion resistance of the Sn-bearing steel under atmospheric conditions is attributable to the retardation of the anodic reaction during drying by Sn ions.

In the case of metals, it is considered that the crystal grain refinement due to plastic deformation is caused by the operation of various slip systems in a grain. In order to understand the initial stage of the grain subdivision, a simple shear test was performed on a low-carbon-steel polycrystal having an average grain size of approximately 150 μm.

After the application of 10% shear, several regions having different slip lines were observed in a grain. The slip lines were explained by {110}<111> slip-system of body-centered cubic iron, and the operated Burgers vectors were estimated. The crystal orientations were different for the subdivided regions, and misorientation angles of the crystal rotation were approximately 10°. The rotation axes of the crystal rotation across the subdivided regions were determined. The rotation axes were almost perpendicular to either of the estimated Burgers vectors in the subdivided regions. The directions of the rotation axes are discussed.

Phase equilibria among the refractory bcc solid solution (bcc_ss), B2, and Laves phases in Nb-Cr-NiAl and Nb-V-NiAl isothermal sections were studied with the aim of introducing the NiAl-B2 phase and/or Al-containing Laves phase for improvement of the oxidation resistance of the bcc_ss phase as an Al reservoir layer for the Al₂O₃ surface layer. Laves phases appear in a wide composition range in both of the isothermal sections, which prevent equilibration of NiAl-B2 with the Nb-rich bcc_ss phase. The geometrical model proposed by Edwards was applied to understand the site-substitution behavior of the multi-component AB₂ Laves phase. In the Nb-Cr-NiAl, Nb-V-NiAl, and Nb-Mo-NiAl systems, the site-substitution behavior of the Laves phases could be explained by comparison of the average atomic diameters of NiAl-B2, Cr, V, and Mo.

A high-purity palladium film with a three-dimensional nanoporous structure was fabricated from a reactive sputtered Al–N–Pd alloy film by a dealloying method that used citric acid chelation. Its characteristic porous structure could be controlled by the concentration of nitrogen gas in the Ar sputtering gas. The added nitrogen gas inhibited the formation of the intermetallic Al₄Pd phase in the as-deposited film, thereby improving the purity of Pd in the dealloyed nanoporous Pd film up to 99 at%. Furthermore, the formed structure of the dealloyed film changed with the nitrogen gas concentration during initial sputtering, i.e., the structure of the film could be controlled from a three-dimensional nano-network to an aggregated nanoparticle-like structure with increasing N₂ gas concentration.

It has been reported that hydrophilicity and hydrophobicity of implants influenced the bioactivity. However, it is hard to maintain the hydrophilicity in case of being stored in air. So it is critical to find a way to maintain implants’ hydrophilicity. In general, silicate has been known to contribute the hydrophilicity. In this study, the silicate containing CaTiO₃ films have been prepared on Ti substrates by two-step treatment for biomaterial applications. The hydrophilicity, osteoconductivity and protein adsorption of treated specimens have been investigated. The 1st step treatment for Ti is to form TiO₂ as precursors, either by anodizing in sulfuric acid solution at 298 K, liquid phase oxidation in nitric acid solution with hydrogen peroxide at 353 K, or thermal oxidation at 673 K in air. Hydrothermal treatment in silicate containing alkaline solution is the 2nd step to convert TiO₂ to silicate containing CaTiO₃ films. The SEM, XRD, XPS, WCA (water contact angle) investigations and protein adsorption measurements have been carried out to characterize the surface properties. This surface maintained 10 deg. in WCA after 7 d exposure in air, while the specimen without silicate has WCA of more than 40 deg. The osteoconductivity is evaluated based on the contact ratio of formed hard tissue on the implanted specimens after 14 d implantation in rats’ tibia at in vivo test. The as-prepared film not only has exhibited smooth and superhydrophilic surface, but also has achieved high osteoconductivity and great protein adsorption capacity.

This review confirms that the Love equation which connects the load on a rigid cone loaded normally on an elastic half-space, and its penetration into the half space, has been verified by several theoreticians. Furthermore, the predictions of the Love equation have been experimentally validated. It is argued here that a modification of the Love equation made about 20 years ago is incompatible with several theoretical treatments as well as with the expression for radial surface particle displacement outside the contact. Moreover, it is also shown that normal loading behaviour of a rigid cone on an elastic half-space cannot be likened to that of the normal loading behaviour of a rigid three-sided or a four-sided pyramid. Lastly, corrections are made to some important expressions given in a well cited paper by Sneddon (1965).

In this study, the effect of Cl removal in bottom ash via a carbonation treatment with CO₂ was investigated by comparing it with a water washing treatment. First, this was also focused on examining the existence of Cl contained in the bottom ash. The overall (soluble and insoluble) Cl content was close to that of bottom ash with fine particle. Next, the washing with water was confirmed and it was not effective in decreasing the Cl content because of the existence of insoluble Cl. Whereas, the removal effect of Cl via carbonation with CO₂ was very high compared to the washing treatment because of the decomposition of Friedel’s salt (main insoluble Cl).

In addition, the kinetics data pertaining to the decomposed Friedel’s salt as the carbonation process proceeds was confirmed. The theoretical was well fitted to the kinetics data. The variation of the rate is constant upon decomposition with the reaction temperature followed the Arrhenius equation (19.676 kJ/mol of activation energy) and the orders with respect to water-to-solution and particle size were also obtained. The decomposition rate of Friedel’s salt based on diffusion through the product layer of shrinking core model could be expressed by the equation.

In this study, pH measurement was performed in a thin electrolyte droplet with a thickness <1000 µm by the measurement of the equilibrium electrode potential of an Sb/Sb_xO_y electrode used as a pH sensor. The equilibrium potential of the Sb/Sb_xO_y electrode was evaluated by using the Kelvin probe (KP) technique. To investigate the potential response of the Sb electrode in a thin electrolyte droplet, the dependency of the Volta potential difference between the Sb and a gold wire as a KP on electrolyte droplet thickness was measured. The Volta potential difference had a linear response with respect to the buffer solution pH, independent of the droplet thickness. This result indicates that the KP technique, combined with an Sb electrode, is sensitive to the pH of a thin electrolyte droplet of thickness ≥50 µm. This pH measurement technique was also applied to measure pH in a corrosion model of steel. The corrosion model consisted of two steel plates in the same plane as the anode and cathode, with a constant current between them. During the corrosion process, the pH value decreased from 6 to 5 near the anode and increased from 6 to 12 at the cathode. The changes in pH measured in the thin electrolyte droplet were in good agreement with the color changes of the solution containing pH indicators.

The compressive deformation behavior and magnetic volume susceptibility were investigated for Au₂CuAl biomedical shape memory alloys in a compositional range from 25 to 45 mol%Cu. Compression tests revealed that the stress for martensite variant reorientation was 282 MPa in Au₂CuAl, and the value increased with the Cu content. On the other hand, the slip stress was higher at intermediate compositions. Moreover, intergranular fracture was suppressed during compressive deformation. Calculated antiphase boundary (APB) energies suggest the dissociation of superlattice dislocation, which leads to the active slip of 〈111〉-type. The measured magnetic volume susceptibility was −2.7 × 10⁻⁶ in Au₂CuAl, hence, this alloy is judged to be metal-artifact-free in magnetic resonance imaging (MRI). The magnetic susceptibility increased up to +7.0 × 10⁻⁶ with increasing Cu content.

We study plastic flow in the vicinity of an indenter-material interface in wedge indentation of aluminum using high speed in situ imaging and particle image velocimetry (PIV) analysis. Displacement and strain fields in the indentation zone are obtained at high-resolution for different indenter angles and two lubrication conditions. These fields can be used to demarcate essential features of the material flow phenomena. The deformed layers close to the indenter wall fit a classical boundary layer profile in the framework of a Bingham-solid. Equivalent Bingham viscosities and boundary layer scaling relations are obtained. The viscosity values appear to reflect the nature of the friction interaction at the indenter-material interface and can potentially be used as a discriminating parameter for evaluating contributions to deformation and dissipation arising from interface friction.

In the present study, a newly established in situ indentation technique by the use of an optically transparent indenter and an immersion liquid, so-called “modified optical indentation microscopy”, was applied for an investigation on the plastic deformation behavior of various samples during indentation. In this technique, the gap between the indenter and the specimen surface is filled with the immersion liquid such as silicone oil and kerosene to widely observe the specimen surface during indentation. In the in situ observations by this technique using polycrystalline pure Mg, the occurrence of various plastic deformation mechanisms and the increase of the anisotropic contact area during indentation can be recognized. Moreover, the increase and the decrease of the contact area which is corresponding to superelasticity during indentation were observed by this technique using the TiNi superelastic alloy. The results of the in situ observations were consistent with the analysis results based on the Hertz theory.