Metal matrix composites (MMCs) were produced using iron (Fe) and niobium carbide (NbC) powders and synthesized with different NbC contents (0, 5, 10, and 20 wt.%) by high energy ball milling. As a result, a Fe_0.99Nb_0.01 solid solution was formed, which influenced the lattice distortion and peak shift. The Fe-NbC composites were subsequently consolidated by rapid sintering at 850°C and sintering pressure of 60 MPa. The hardness of Fe-NbC composites were ranged from 128.9±10.4 to 374.5±14.6 kg/mm², which was related to the hall petch relationship. This enhancement is attributed to the dispersion strengthening effect of the agglomerated powders through high energy ball milling, and the control of grain growth by the spark plasma sintering. Particularly, the oxidation resistance of Fe-NbC composites increased gradually as the NbC contents increased, indicating that the oxidation layer such as Nb₂O₅, Fe₂O₃, and Fe₃O₄ locally formed on the Fe-NbC composites surface. The oxidation layer decreased from 204.34 to 12.99 μm with the rise in NbC content.

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The monitoring of invasion/permeation hydrogen on entry/exit surfaces of cathodically charged SUS316 columnar crystals was conducted with a scanning Kelvin probe force microscope (SKPFM) under atmospheric pressure. Columnar crystal specimens covered with oxide films on their surfaces under room conditions were prepared for cathodic charging tests and subsequent SKPFM measurements. The invaded hydrogen on the entry surface was detected at the δ-ferrite phases for 7 d after charging, and the segregation of invaded hydrogen at the boundaries between the δ-ferrite and austenite matrix was prolonged for >10 d after charging. The permeated hydrogen on the exit surface was detected at the δ-ferrite phases for 3 d after charging, but was not substantial at some of the δ-ferrite phases regardless of the charging. Segregation of permeated hydrogen at the boundaries between the δ-ferrite and some of the intermetallic precipitates was prolonged for 7 d after charging. The behaviors of invaded/permeated hydrogen based on heterogeneous microstructures are discussed to improve understanding of the hydrogen embrittlement mechanism in weld metals.

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In this study, the electrical properties and stability of silver nanowire transparent conductive electrodes (TCEs) were improved through the platinum electroplating process (AgNWs@Pt TCEs). After electroplating, environmental and thermal stabilities increased considerably, whereas sheet resistance was greatly reduced. Sheet resistance sharply decreased from 181.3 Ω/□ to 16.59 Ω/□. Meanwhile, the thermal stability of the AgNWs@Pt TCEs was enhanced by 20 °C compared with that of TCEs based on silver nanowires. The sheet resistance of the AgNWs@Pt TCEs remained nearly constant after exposure to ambient air for five months. The optimal electroplating condition was achieved at an electroplating current of 10 µA for 30 s. Under this condition, the sheet resistance, transmittance, and figure-of-merit (FOM) values of the AgNWs@Pt TCEs were approximately 16.59 Ω/□, 83.89%, and 123 Ω⁻¹, respectively.

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The aluminum alloy shell fabricated by 'bending + high-frequency welding' is the core component of the Chinese new energy vehicle battery pack. Still, this process cannot produce the next generation of shell products with unequal wall-thickness. In this study, we take the unequal-wall-thickness square 3003 aluminum alloy battery shell with a wall thickness of less than 0.5mm and a tolerance range of ±30μm as the research object. According to the cold work, hardening characteristics of 3xxx series aluminum alloys, hot extruded hollow blanks were prepared, and a new cold drawing process was attempted to be developed on this basis. Based on the analysis of the stress-strain field during cold drawing of defective workpieces, the size of the die inlet's R angle and the blank's size were optimized to solve the problems of local fracture and tearing of the blank. The results show that the maximum stress during cold drawing occurs at the fillet where the sizing zone intersects with the wall-thinning zone. This location is subjected to tensile stress, normal pressure from the inner and outer dies, and tangential friction force, causing a material accumulation phenomenon; the material flow velocity along the cold drawing direction is inconsistent, which will cause U-shaped patterns on the surface of finished products; the strain value along the cold drawing direction first increases and then decreases with the rise of R angle, reaching the maximum when the R angle size is 1.5mm. After optimization, the maximum equivalent stress decreased from 205MPa to 190MPa, and the average strain along the cold drawing direction increased from 0.15-0.22 to over 0.3. This study successfully prepared precisely ultra-thin lithium iron phosphate battery shells by optimizing cold drawing process parameters and die structure.

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The use of biosynthesis is considered an environmentally friendly and more sustainable method for the production of metal nanoparticles. In this study, copper nanoparticles (Cu-NPs) were synthesized using tea stem extract as a reducing agent. Spectroscopic identification revealed that the CuO is the major crystalline structure with a particle size of 14.9 nm. The B_g mode of the Raman active mode is associated with the symmetric oxygen stretching of Cu-O and is consistent with the monoclinic crystal CuO in X-ray powder diffraction (XRD) measurement. X-ray photoelectron spectrometer (XPS) deconvolution revealed the split peaks for Cu 2p_3/2 and confirmed the coexistence of Cu⁺ and Cu²⁺ in the Cu-NPs. The Cu-NPs possessed effective catalytic ability for the degradation of methylene blue (MB) from the aqueous phase in a Fenton-like system. These results provide important evidence for the potential application of tea stem in synthesis of nanoparticle.

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Pure magnesium and Mg-(0.2-0.9 at.%) Y rolled sheets were subjected to three-point bending tests to individually investigate the effects of texture and yttrium addition on bending deformation behavior. Yttrium addition increased bending yield stress in both Specimen TR with the neutral plane parallel to the rolled plane and Specimen TN with the neutral plane perpendicular to the rolled plane, resulting from the increase in critical resolved shear stresses (CRSSs) for basal slip and {1012} twinning with yttrium addition. Bending ductility increased with increasing yttrium addition until 0.5 at.% yttrium addition, and then decreased at 0.9 at.% yttrium addition in Specimen TN. On the other hand, bending ductility increased until 0.9 at.% yttrium addition in Specimen TR since non-basal slip activities increased with increasing yttrium addition. Since neutral planes in Specimen TN with 0.9 at.% yttrium addition moved more to the center than those in Specimen TN with 0.5 at.% yttrium addition, resulting in the higher tensile strain at the tension side. Therefore, the bending ductility in 0.9 at.% yttrium addition was lower than that in 0.5 at.% yttrium addition.

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Empirical formulas were derived for the interface shape, mechanical properties, and electrical characteristics of accumulative roll bonded (ARB) Cu/Nb laminated materials, based on relevant literature data. These formulas were incorporated into a forward analysis model using finite element analysis, enabling the calculation of yield stress and conductivity from the spatial distribution of Cu/Nb two phases. By randomly varying the layer thickness and interface shape in the two-phase spatial distribution and conducting repeated forward analyses, a database linking microstructural descriptors with yield stress and conductivity was created. These microstructural descriptors include volume fraction, geometric features, topological features, spatial correlation functions, and persistent homology. The significance of each microstructural descriptor on yield stress and conductivity was quantified using machine learning techniques. The results revealed that the Cu volume fraction, layer thickness, and 0th Betti number are crucial for yield stress, while for conductivity, the Cu volume fraction has the strongest influence, followed by layer thickness and layer continuity. Based on these outcomes, the Pareto front for ARB Cu/Nb laminates in the strength-conductivity space was presented.

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Die casting has many advantages, such as high precision, mass production, and excellent recyclability. However, gas defects in the product have become a problem. One countermeasure to this problem is to design the injection input of the plunger appropriately. Recently, CFD has been used to design plunger injection inputs, and by combining with optimization techniques, auto-design of plunger injection inputs has been possible. However, CFD is difficult to apply because of the high cost of CFD resources, the need to resource IT engineers, and the time required for its auto-design. Therefore, we propose a new injection input design method based on an algebraic approach, enabling anyone to design a plunger injection input that prevents gas defects with ease and at a low cost. Simulation and experimental results verified the effectiveness of the proposed method.

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A residue containing TiO₂ and PGMs is generated in the hydrometallurgical process used for recycling platinum-group metals (PGMs). In this study, a pyrometallurgical process was considered in which PGMs from the residue generated in the hydrometallurgical process were concentrated in a molten copper phase as a collector metal and TiO₂ was separated into the SiO₂–CaO–TiO₂ slag phase with SiO₂ and CaO flux. The dissolution of PGMs must be reduced to minimize the loss of PGMs to the slag. Therefore, the distribution ratios of Pt as representative PGMs between the liquid SiO₂–CaO–Al₂O₃–TiO₂ or liquid SiO₂–CaO–TiO₂ slag and molten copper were measured at 1773 K under an oxygen partial pressure of p_O2 = 10^-10. The experimental results showed that the distribution ratio of Pt increased with TiO₂ concentration in the slag, and the distribution ratio of Pt reached a maximum value at a TiO₂ concentration of approximately 10 mass%, and decreased with a further increase in TiO₂ concentration with the SiO₂–CaO–Al₂O₃–TiO₂ slag. However, as TiO₂ concentration in the slag increased, the distribution ratio of Pt decreased with the SiO₂–CaO–TiO₂ slag. Additionally, the experimental results showed that the distribution ratio of Pt between the SiO₂–CaO–Al₂O₃–TiO₂ slag and liquid copper increased with the slag basicity B, defined as B = (mass%CaO)/(mass%SiO₂) when the TiO₂ concentration in the slag was greater than 10 mass%.

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The Heusler-type Fe₂VAl alloy is a promising candidate for use in fabricating a thermoelectric power generation device because of its large Seebeck coefficient and high electrical conductivity. However, the high thermal conductivity of this alloy, as a thermoelectric material, degrades its power generation capacity. In this study, to reduce its thermal conductivity, the microstructure of a sintered Fe₂V_1.08Al_0.92 alloy prepared via a powder metallurgical process was modified by adding oxide nanoparticles. Via the dispersion of Al₂O₃ nanoparticles, a sintered Fe₂V_1.08Al_0.92 alloy with fine grains of approximately 200 nm in size was obtained due to the pinning effect on grain growth during sintering. The thermal conductivity was reduced from 16 to 11 W/mK. Upon La₂O₃ addition, the grain size of the Fe₂V_1.08Al_0.92 alloy was reduced to approximately 100 nm and the thermal conductivity was further reduced to 10 W/mK. The difference in grain refinement could be caused by the lower stability of La₂O₃, which facilitated dispersion during ball milling, compared to that of Al₂O₃. As these microstructure refinements negatively affected the electronic properties, the thermoelectric performance of the Fe₂V_1.08Al_0.92 alloy could not be enhanced. However, partial microstructure refinement with sparsely distributed La₂O₃ could slightly enhance the thermoelectric performance due to an appreciable reduction in the thermal conductivity without a considerable degradation in the electronic properties. By using these thermoelectric properties, a simple estimation of thermoelectric power generation, assuming a thermal resistance between the heat sources and thermoelectric module, was conducted. Remarkably, the results suggested that the reduction in thermal conductivity could enhance the output power density and conversion efficiency and reduce the optimal leg length. Thus, practically, controlling the balance between the electronic and thermal properties via microstructural modification is favorable in improving the practicability of the Fe₂VAl alloy by enhancing the power generation capacity and reducing the sizes and masses of thermoelectric devices.

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Announcement Concerning Article Retraction
The following paper has been withdrawn from the database of Mater. Trans., because a description based on a misinterpretation of the experimental results was found by the authors in advance of publication after acceptance.
Mater.Trans. 52(2011) Advance view.
Improvement in Fatigue Strength of Biomedical β-Type Ti-Nb-Ta-Zr Alloy while Maintaining Low Young’s Modulus through Optimizing ω-Phase Precipitation

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