In milling processes involving roughing and finishing operations, machining conditions selected during process planning not only affect machining efficiency but also influence the surface quality of subsequent finishing stages. However, the selection of machining parameters is still largely based on empirical knowledge, and the quantitative relationship between process efficiency, machining load, and surface roughness remains insufficiently clarified. To address this issue, this study proposes a digital twin–based decision-support framework to systematically analyze machining performance and surface quality in milling processes.

In the proposed approach, CAM-generated roughing and finishing G-code programs are analyzed using two complementary digital twin tools: Siemens Run My Virtual Machine (RMVM) for machining time estimation and MACHPRO for cutting force simulation. A three-level full factorial design is adopted to configure axial (AP) and radial (AE) machining parameters, enabling systematic evaluation of their effects on machining time and cutting force without extensive trial machining.

Representative machining conditions are then validated through physical finishing experiments, with surface roughness (Ra) measured as the primary quality indicator. Experimental results show that machining time and cutting force exhibit opposing trends with respect to AP and AE variations, revealing an inherent trade-off between process efficiency and machining load. Cutting force is further shown to correlate strongly with surface roughness trends, indicating its effectiveness as a process indicator for surface quality variation.

To support dual-objective decision-making, Gaussian Process Regression (GPR) is employed as a trend-fitting tool to construct continuous surrogate representations of machining time and cutting force, from which a Pareto front is derived. This Pareto-based representation enables flexible selection of cutting conditions according to different production requirements. The results demonstrate that the proposed digital twin–based framework can significantly reduce the reliance on extensive trial-and-error experiments during process planning.

By integrating simulation-driven evaluation, experimental validation, and Pareto-based decision analysis, suitable cutting parameter combinations can be identified in a virtual environment and directly transferred to actual machining, achieving a desirable balance between machining efficiency and surface quality in milling processes involving roughing and finishing operations.

Accurate material modeling is critical for reliable finite element simulation of aluminum extrusion processes. This work presents the development and industrial validation of a strain-compensated Arrhenius constitutive model for AA7075 aluminum alloy applied to porthole die extrusion. Isothermal compression experiments were performed using a Gleeble 3500 system at 450–500°C and 0.1–1.0 s⁻¹. Material constants were determined as sixth-order polynomial functions of strain, yielding a model with R = 0.997 and AARE = 1.50%. The constitutive relations were incorporated into the QForm software to simulate the extrusion of a complex curtain wall profile through a six-porthole die. Factory trials on a 2100-ton press confirmed the model’s reliability, with predicted forces deviating by only 1.11% from measured values, compared to 19.16% using default database parameters. TS-GHX1 tool steel with gas nitriding treatment was employed to address die failure issues associated with conventional H13 steel, demonstrating 6–8% reduction in peak die stresses and successful extrusion of the target profile.

A metallic sheet radiation device was keenly required for cooling the solar panel and giant antenna in space. Micro- and nano-texturing to metallic sheet surfaces, provided a way to significantly improve the infra-red (IR) emission property from optical insulation of polished metal sheets. Unit cell shape and alignment in this texturing has much influence on the IR-emissivity and the working wavelength range. A simplified theoretical model was proposed to design the micro-cone shaped unit cell. Two-step procedure was utilized to form the micro-cone textures into the copper sheet via the laser micro-machining and to build up the nickel nanotextures onto the micro-textured surface and copper clearance via the electroplating. IR-emission spectroscopy was used to demonstrate that micro-cone shaped microtextures enhanced the IR-emissivity and that nano-textures worked as a helper to further increase the IR-emissivity.

This study investigates the influence of Al and Ni content on the phase evolution, mechanical behavior, and fracture morphology of CoCrFe-based high-entropy alloys (HEAs). Quasi-static compression and dynamic impact tests were conducted to evaluate the sensitivity of these alloys to varying strain rates. X-ray diffraction (XRD) and metallographic analyses indicate that AlCoCrFeNi_2.1 exhibits a single-phase FCC structure and Al_1.2CoCrFeNi_1.9 possesses a dual-phase FCC/BCC structure. Al_1.4CoCrFeNi_1.7 transitions to a fully BCC structure, confirming that increasing Al content stabilizes the BCC phase.

Mechanical testing reveals that yield strength and flow stress increase with rising strain rates. This trend is attributed to significant lattice distortion caused by solute atoms, which effectively hinders dislocation motion and provides solid-solution strengthening. Scanning electron microscopy (SEM) of fracture surfaces shows that quasi-static failure is characterized by fish-scale dimples. In contrast, dynamic impact failure features a combination of tear dimples and cleavage facets, indicating a significant reduction in ductility at higher strain rates.

This study investigates the effects of molding-sand moisture content and compositional variations on the fluidity behavior and microstructural evolution of ductile and gray cast iron during mold filling. Green molding sands with varying moisture levels and formulations were prepared to create standard fluidity-test molds. The chemical composition of the molten iron, pouring temperature, and sand-mold parameters were systematically analyzed to evaluate their synergistic effects on melt fluidity and solidified microstructures. Metallographic analyses were performed on selected sections along the flow path to characterize microstructural changes arising from melt–sand interactions. Experimental measurements—including temperature gradients, flow velocity, and compositional depletion—were incorporated into a predictive model for flow length, which was validated against experimental results. The findings reveal that temperature reduction and elemental loss at the flow front significantly restrict the practical fluidity of molten cast iron, while contributing to microstructural degradation and diminished surface quality. This work provides new insights into flow-front chemical evolution and offers a framework for predicting fluidity and surface-quality outcomes in green-sand casting processes.

This study focuses on developing an internal state variable (ISV) model for predicting the flow stress and microstructure evolution of pure copper subjected to cold drawing. The experimental work involved cold drawing of oxygen-free copper to a cumulative strain of 8.1, followed by tensile testing and microstructural analysis using electron backscatter diffraction. Observations revealed progressive grain refinement and transition from low-angle grain boundaries (LAGBs) to high-angle grain boundaries (HAGBs) attributable to continuous dynamic recrystallization (cDRX). The ISV model, incorporating dislocation dynamics and cDRX, successfully predicted trends in flow stress and microstructural characteristics, although certain discrepancies highlight the need for further model refinement. This research advances our understanding of copper’s response to deformation and supports enhanced modeling approaches for industrial applications.

Flatness defects in hot-rolled coils are primarily caused by non-uniform plastic deformation introduced during continuous processing. Each stage of the coil production line can contribute to such deformation. In the absence of effective analytical tools, issues like the C-bow defect have traditionally been addressed through empirical, trial-and-error methods. This study presents a method for identifying the fundamental mechanism responsible for the C-bow defect by employing residual stress measurement and analysis techniques. As the distribution of residual stress reflects the cumulative plastic deformation induced throughout the production process, the slitting method was adopted to obtain through-thickness stress profiles. Analysis of the residual stress characteristics enabled identification of the dominant deformation mechanisms. Based on these findings, a high-speed cooling strategy is proposed to improve material strength and minimize coiling induced deformation. The implementation of this approach demonstrates notable improvements in sheet flatness.

High-strength aluminium alloys of the 7xxx series, particularly AA7075-T6, present significant challenges during conventional cold forming due to their limited ductility, high flow stress, and pronounced springback, which restrict the manufacturability of complex structural components. In this study, a comprehensive experimental and analytical investigation is conducted to evaluate the warm forming behaviour and forming limits of AA7075-T6 by integrating tensile testing, hardness evolution, transmission electron microscopy (TEM), and forming limit diagram (FLD) analysis. Solution heat treatment (SHT) optimisation demonstrated that a holding time of 15 min at 477°C is sufficient to achieve complete precipitate dissolution, yielding mechanical properties and hardness recovery comparable to longer treatments while substantially reducing processing time. Warm tensile tests performed over a temperature range of 100–180°C and strain rates of 0.1–1.0 s⁻¹ revealed a pronounced reduction in flow stress and enhancement in ductility relative to room-temperature forming. An optimal forming window was identified at 160°C and 0.5 s⁻¹, achieving up to a 28% reduction in ultimate tensile strength while maintaining high elongation. Strain-assisted ageing led to significant post-forming hardness enhancement due to dislocation-assisted precipitation, with peak hardness exceeding the original T6 condition under appropriate ageing temperatures. FLD results showed a clear expansion of the safe deformation domain with increasing forming temperature, indicating delayed strain localisation and improved biaxial formability. The experimentally determined forming limit curves were accurately represented using a shifted parabolic model implemented in MATLAB, enabling consistent quantitative comparison across different forming conditions. TEM analysis revealed deformation-induced microstructural evolution, including dislocation structures and precipitate–dislocation interactions, which directly govern strain redistribution and forming limits. The combined experimental–analytical framework establishes a clear structure–formability relationship and confirms that warm forming is an effective and industrially viable strategy for improving the formability of AA7075-T6 while preserving or enhancing mechanical performance.

High efficiency of electric motors is an essential requirement for an electrified society. Amorphous electrical steel sheets are supplied as thin foils with a thickness of approximately 25 µm and exhibit a high tensile strength of about 2.2 GPa, limited elongation of around 1%, and a high hardness exceeding 900 HV. During the shearing process of motor cores, these materials tend to exhibit brittle fracture behavior, and their high hardness often leads to frequent tool damage. To suppress tool damage, introducing a chamfer at the punch edge is an effective approach to avoid excessive stress concentration during shearing. However, the chamfer length in the punch stroke direction induces inward drawing of the work material toward the die center during shearing, resulting in bending deformation and crack formation on the punched hole surface. In this study, a chamfer of 20 µm was introduced in the radial direction at the punch edge, and an additional chamfer of 1–2 µm was provided in the stroke direction. Furthermore, a condition with a nano-texture applied to the punch surface was also prepared. Half-shearing experiments were conducted on amorphous electrical steel sheets to observe crack initiation behavior, and the fracture propagation and fracture mechanisms were discussed.

Industrial pick-and-place automation requires rapid inspection of PU suction cups (vacuum cups) whose defects are subtle, low-contrast, and expensive to annotate at the pixel level. To address the combined challenges of normal-only training and shop-floor latency constraints, we propose SpecMamba-AD, an unsupervised teacher–student knowledge transfer framework for fine-grained defect localization in high-resolution industrial images. SpecMamba-AD pairs a frozen ImageNet-pretrained CNN teacher with a lightweight hybrid CNN–Mamba student. A blur-pooled, anti-aliasing CNN stem mitigates resolution-induced aliasing and token explosion, while Mamba blocks capture long-range structural consistency under limited memory. Training follows a denoising feature regression paradigm: the student receives synthetically corrupted inputs and is optimized to regress the teacher’s clean multi-level features, producing a discrepancy-based anomaly map at inference. To enhance sensitivity to micro-defects dominated by high-frequency cues, we further introduce a log-magnitude spectral loss that constrains teacher–student alignment in the frequency domain. Extensive experiments on PU suction cups data demonstrate that SpecMamba-AD achieves strong detection and localization performance under a strict normal-only protocol, and remains robust under realistic shifts in product line, illumination, and resolution supporting practical deployment for real-time quality assurance and stable grasp reliability.

Three types of punch were prepared for sharing the oxygen-free copper sheets with the thickness of 0.5 mm; Normal punch with sharp edge, Lapped punch, and Nitrided-lapped punch. The smooth sheared surface with the smallest fractured area ratio and shear-droop was obtained using the Nitrided-lapped punch. No adhesion of active copper fresh surfaces was detected on the Nitrided-lapped punch surface. The work materials deformed along the smooth punch surface without adhesive wear due to the chemical inertness of Nitrided-lapped punch.

Fine blanking punch edge profile was designed to control the local metal flow around the edge by chamfering technique. Massive nitrogen supersaturation (MNS) was utilized as a surface treatment of chamfered edges, corners and punch surfaces. MNSed SKH51 square punch with the chamfered edges was used for finer blanking of AISI304 austenitic stainless-steel sheets. The edge profile distortion was significantly reduced from normal blanking with and without edge chamfers. The burr height of blanks was also reduced so that dimensional accuracy in fine blanking was improved together with punch-life extension by the present punch design.

This study proposes a framework for estimating wear phenomena that affect die life in press forming. Dynamic signals during forming were measured using a three-axis piezoelectric force sensor and an acoustic emission (AE) sensor, and wear-related features were extracted from the load and AE data. These features enabled discrimination of adhesive wear, ploughing wear, and delamination. The proposed approach is expected to contribute to improved die life prediction and productivity in press forming.

Hot-stamping technology has evolved from single-thickness components to differential-thickness tailor-welded blanks (TWBs). This study investigates the tensile deformation behavior of equal-thickness (1.2/1.2t) and differential-thickness (1.2/1.8t) hot-stamped TWBs using CAE and Digital Image Correlation (DIC). Results show high consistency between simulations and experimental data. The 1.2/1.2t and 1.2/1.8t TWBs exhibit distinct deformation mechanisms. In 1.2/1.2t specimens, both sides undergo uniform deformation before strain localizes in the necking zone. Conversely, deformation in 1.2/1.8t TWBs is primarily concentrated in the 1.2t section. The 1.8t side experiences very limited deformation and remains elastic even as the thinner side reaches fracture. Furthermore, the Gauge Length (GL) significantly influences measured elongation. A longer GL averages localized necking deformation over a larger span, underestimating the material’s actual elongation capacity, particularly when spanning the nearly undeformed 1.8t region. To accurately reflect true elongation of the material, measurements should exclude regions with limited deformation. These findings provide critical insights for the automotive industry in evaluating the ductility of hot-stamped TWB components.

The present work reports a study on nonlinear dielectric properties of the relaxor ferroelectric of lead magnoniobate - scandoniobate (PMN-PSN) prepared in a solid solution form with a component ratio of 0.55:0.45. The results of linear dielectric properties are also provided for comparison. A combination of Scanning Electron Microscopy - Energy Dispersive Spectroscopy (SEM-EDS), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) was employed to characterize the synthesized material. The nonlinear dielectric spectroscopy was analyzed based on higher current harmonics under an applied harmonic electric field. The obtained results indicated the existence of the so-called “superparaelectric” state within a temperature range from 306 K to 459 K, characterized by polar nanoregions embedded in a paraelectric matrix. Besides, at temperatures below 306 K, an external electric field induced a ferroelectric state, whereas a transition to a conventional paraelectric phase was observed above 459 K. The data confirmed the high sensitivity of relaxor systems to external stimuli and enabled a detailed tracing of the evolution of polar order over a wide temperature interval.

High–temperature deformation and dynamic recrystallization (DRX) behaviors of Cu–Sn–P alloy were systematically investigated comparing with those of Cu and Cu–P alloy. Annealing behavior of post DRX was also examined. Addition of P and Sn to Cu increased deformation stress at elastic region as well as those at plastic deformation region such as peak and steady–state flow stresses. Especially, the effects of Sn were notably large and, hence, onset of DRX was much delayed. Sn addition also influences the reduction of DRXed grain size and strongly impeded grain coarsening during annealing after DRX. 3D–atom probe tomography analysis revealed enrichment of P and Sn at grain boundary and the areas nearby grain boundary. This result strongly suggested formation of P-Sn atom pairs at grain–boundary region, which had the effect of retarding grain–boundary migration by the elastic interaction between P–Sn atom pairs and grain boundary and, hence, resulted in raising deformation stresses.

This Paper was Originally Published in Japanese in J. Japan Inst. Copper 64 (2025) 93–100. The main text and Table 3 have been slightly modified.

The active deformation mode (slip systems and twinning) of extruded AZ31B alloy (Mg-3Al-1Zn, mass%) during compression at RT, 100°C and 150°C was investigated by visco-plastic self-consistent (VPSC) simulation. Compression tests were first performed to obtain compression curve of AZ31B. The VPSC model was fitted to the compression curves to estimate the Voce hardening parameters which are required for the VPSC simulation. In the case of compression along the extrusion direction, work-hardening occurred rapidly with the transition of dominant deformation modes at all temperatures. In the case of compression to the other directions, basal 〈a〉 slip was dominant throughout the deformation at all compression temperatures. In addition, prismatic 〈a〉 slip and tensile twin were active in the early stage of deformation, and pyramidal 〈c + a〉 slip became active in the later stage of deformation. Pyramidal 〈c + a〉 slip became more active with increasing temperature from RT to 100°C, whereas basal 〈a〉 and prismatic 〈a〉 slips became more active with increasing temperature from 100°C to 150°C. These different trends in the change of the active slip system with increasing temperature can be attributed to the CRSS maximum of the pyramidal 〈c + a〉 slip located around 100°C.

This Paper was Originally Published in Japanese in J. JILM 74 (2024) 73–82.

Thermal conductivity is one of the important parameters for accurately predicting subsurface temperature structures in various geoengineering applications, such as geothermal development and the underground disposal of radioactive wastes. Thermal conductivity varies with rock type and is anisotropic when rocks such as shale and schist are layered. Sedimentary rocks, especially sandstone and mudstone, have layer structures that are formed by consolidation and exhibit reduced porosity. Although this porosity change may be linked to the anisotropy of thermal conductivity, this relationship has not been previously investigated. In this study, we quantitatively investigated the anisotropy of the thermal conductivity of sedimentary soft rocks and then examined the relationships between porosity and the anisotropy of thermal conductivity. In addition to thermal conductivity, the anisotropy of the P-wave velocity was also examined, as it is known to correlate well with thermal conductivity. The thermal conductivity and P-wave velocity were measured both perpendicular and parallel to the bedding plane in the sample. Cubic samples of sedimentary soft rocks taken from the Boso Peninsula of central Japan, whose porosity levels ranged from approximately 37% to 55%, were used. As a result, the thermal conductivity and P-wave velocity of the samples that were parallel to the bedding plane were greater than those that were perpendicular to the bedding plane, indicating that anisotropy was observed for these physical properties in terms of the bedding plane. The degrees of anisotropy regarding to bedding plane of both physical properties were then quantitatively evaluated by two indices. The results showed that the degrees of anisotropy degrees of thermal conductivity and the P-wave velocity were linked to porosity; the degree of anisotropy in the low-porosity specimens tended to be lower than that in the high-porosity specimens.

This Paper was Originally Published in Japanese in J. Soc. Mater. Sci., Japan 73 (2024) 205–211. The Abstract has been slightly modified.

Since the internal temperature of lithium-ion batteries rise to 80°C during charging or discharging, this study investigated the macroscopic creep properties at high temperature of negative electrodes in lithium-ion batteries and their estimation methods based on the microscopic structure of the electrodes. Tensile and creep tests at several temperature levels were conducted on a negative electrode consisting of carbon powder and polyvinylidene fluoride (PVDF) binder. The stress-strain curve, the time history of the tensile strain, and the creep rupture time were measured in these tests and estimated using the simple model proposed in this study. The proposed model approximates the alignment of carbon particles as body-centered cubic (bcc) or face-centered cubic (fcc). The test results showed that the stiffness and the strength of the negative electrode decreased with the increase of the test temperature. The PVDF binder gradually shrank in the creep test at high temperature. This affected the creep properties of the negative electrode. The time history of the tensile strain and the creep rupture time were located between the upper and lower limits of the proposed model taking the thermal shrinkage of the PVDF binder into account.

This Paper was Originally Published in Japanese in J. Soc. Mater. Sci., Japan 75 (2026) 143–150.

It is important to understand the long-term migration of radionuclides when considering long-lasting rock engineering projects such as the geological disposal of radioactive waste. The network of fractures and pores in a rock mass plays a major role in fluid migration as it provides pathways for fluid flow. The geometry of such a network can change due to fracture sealing by fine-grained material over extended periods of time. Groundwater commonly contains fine-grained material such as clay minerals, and it is probable that such minerals accumulate within rock fractures during groundwater flow, thereby decreasing fracture apertures and bulk permeability. It is therefore essential to conduct permeability measurements using water that includes fine-grained minerals in order to understand the evolving permeability characteristics of rock. However, this has not been studied to date in in-situ rock mass. Therefore, in the present study, we perform permeability measurements in a granite rock mass to investigate the change of permeability that occurs under the flow of water that includes clays. Our findings show that clay particles accumulate in fractures and that the permeability (hydraulic conductivity) of the granite rock mass decreases over time. The decrease was more significant in the earlier time. We conclude that the accumulation of clay minerals in the fracture decreases the permeability of a rock mass. Furthermore, we consider that the filling and closure of fractures in rock is possible under the flow of groundwater that contains clay minerals.

This Paper was Originally Published in Japanese in J. Soc. Mater. Sci., Japan 73 (2024) 220–225. The caption of Fig. A2 has been slightly modified.

Effects of two kinds of electroless Ni-P plating and a baking treatment after plating on the temperature-dependent hydrogen desorption behavior, tensile properties, and fatigue properties of 6061-T6 aluminum alloys were investigated, and the results were discussed. Thermal desorption analysis (TDA) revealed that each plating causes hydrogen absorption into the substrate, which was found to reduce the mechanical properties. After plating, the baking treatment significantly reduced the hydrogen amount in the substrate and improved the mechanical properties. The fatigue strength of the low-phosphorus type plated specimen was increased to 160 MPa by the baking treatment, and a fatigue ratio of over 50% was obtained.

Based on the hydrogen-vacancy cluster theory, the reduction in fatigue strength of high-phosphorus type plated substrate is assumed to be caused by the formation of hydrogen-induced vacancies due to hydrogen incorporated into the substrate by plating, which migrate and form nanovoids during fatigue testing.

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 89 (2025) 355–361.

Cu-Sn-Ni ternary alloy thick films were electrodeposited from a basic complex bath containing potassium pyrophosphate. The crystal orientation and physical properties such as microhardness and tensile strength were evaluated. The addition of potassium pyrophosphate formed complexes with Cu²⁺, Sn²⁺, and Ni²⁺ ions in aqueous solution, and the electrodeposition potential was shifted to a less-noble direction. The maximum hardness (431 HV_0.1) was obtained from the Cu-4.9%Sn-0.9%Ni alloy film while the maximum tensile strength (1036 MPa) was achieved with the Cu-2.4%Sn-0.3%Ni alloy film. These mechanical properties were enhanced by the solid solution of Sn and grain refinement.

This Paper was Originally Published in Japanese in J. Japan Inst. Copper 64 (2025) 38–43.

In this study, the formation behavior of surface oxide films through low-pressure oxidation was investigated for conventional pure copper, electrolytic copper foil, and electroplated copper materials. Before low-pressure oxidation, pure copper exhibited a microstructure of coarse equiaxed grains, electrolytic copper foil contained a mixture of coarse and fine columnar grains, and the electroplated copper layer consisted of fine grains. After low-pressure oxidation at 700°C, unlike oxidation under atmospheric pressure, Cu₂O films with a particle size of approximately 5 µm grew on the copper substrate in all samples. Furthermore, no detachment or delamination of the oxide films was observed in the cross-cut tape test or the 180° bending test for any sample. These results indicate that, regardless of the initial crystalline structure of the copper substrate, low-pressure oxidation leads to the formation of a dense coating layer composed of large Cu₂O grains, which is strongly bonded to the copper substrate. Therefore, the oxide films formed on electrolytic copper foil and electroplated copper materials are also expected to exhibit high bonding strength, similar to conventional pure copper.

This Paper was Originally Published in Japanese in J. Japan Inst. Copper 64 (2025) 54–58. The figure captions are slightly modified.

The corrosion resistance of hot-stamped zinc-coated steel sheet with a coating layer of the α-(Fe, Zn) phase is proposed based on the structural and electrochemical characterization of corrosion products. Goethite, lepidocrocite, akaganeite, and magnetite are the main corrosion products formed on the uncoated steel sheet. However, when the surface is coated with the α-(Fe, Zn) phase, zinc ferrite is formed instead of magnetite in the inner layer of corrosion products. The formation of zinc ferrite is considered to suppress the cathodic reduction reactions of lepidocrocite and akaganeite, thereby enhancing the corrosion resistance of the steel sheet.

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 90 (2026) 10–16.

To improve the adhesion and corrosion resistance of aluminum, the dual-layer anodic oxide film was formed by sequential anodizing in phosphoric acid (PA) and oxalic acid (OA) electrolytes. The upper-layer anodic oxide film, with large pore diameter and thick barrier layer, was obtained by applying a high voltage in PA electrolyte. While the large pore diameter could improve adhesion, the thick barrier layer hindered the uniform growth of the lower-layer anodic oxide film formed by anodizing in OA electrolyte. To achieve a uniform growth of the lower-layer film, the barrier layer of the upper-layer film was thinned using the current recovery method. Consequently, pores grew continuously at the interface between the upper-layer and lower-layer films, resulting in a uniform film thickness of the dual-layer film. When the dual-layer film was subjected to hot water sealing, few flaky hydrates formed in the upper-layer film and the pores remained open at the surface, whereas many granular hydrates formed in the lower-layer film. Thus, the dual-layer film could improve both adhesion and corrosion resistance of aluminum.

This Paper was Originally Published in Japanese in J. JILM 75 (2025) 525–530.

Most cast products are produced using sand molds, including green sand, organically bonded, inorganically bonded, and special molds. Silica sand is the most widely used material for manufacturing sand molds; however, its utilization presents several challenges, such as pneumoconiosis, risk limited recyclability, and casting defects. Therefore, replacing silica sand with artificial sand is essential. While artificial sand has effectively replaced silica sand in organically bonded molds, achieving a comparable substitution in green sand molds, which are the most widely used, remains difficult. This difficulty arises because, during casting, sintering at the bonding sites between artificial sand particles leads to the formation of sintered layers on green sand molds. These sintered layers are extremely hard to remove, thereby hindering green sand recyclability. This study aims to elucidate the unclear mechanism of sintered layer formation to help its prevent. Artificial sands for casting include mullite-based and alumina-based types. In mullite-based artificial sand, reactions are expected between the artificial sand and bentonite and between molten cast iron and bentonite. In alumina-based artificial sand, reactions are assumed among the artificial sand, bentonite, and molten cast iron, as well as between molten cast iron and bentonite. K₂O, a component of artificial sand, acts as a flux that promotes these reactions. Hence, the formation of sintered layers can be suppressed by reducing the K₂O content in artificial sand.

In near-eutectic aluminum casting alloys, the influence of melt flow on eutectic evolution and the formation of intermetallic compounds remains less well understood than its effect on α-Al grain refinement. In this study, JIS ADC12 alloy containing strontium was solidified under electromagnetic stirring, and microstructural features were quantified by image analysis to clarify those effects. Electromagnetic stirring increased both the spacing and the area of eutectic silicon, indicating suppression of the strontium-induced modification. Intermetallic compounds identified as α-Al(FeMn)Si showed pronounced coarsening, accompanied by a morphological transition from Chinese-script to coarse polygonal forms with increasing current frequency. EDS analysis revealed chromium enrichment in the polygonal grains. Thermodynamic calculations revealed that chromium increases the formation temperature of the α-Al(FeMnCr)Si phase, thereby promoting primary grain formation and subsequent coarsening under melt flow. These findings indicate that externally driven melt flow adversely affects the eutectic refinement induced by chemical modifiers and promotes the grain coarsening of primary intermetallic phases in ADC12 alloy.

Partial non-magnetization is one of the technical approaches to control electromagnetism to improve the characteristics of the motor and is achieved by replacing the soft magnetic component of a rotor core with a non-magnetic material. The objective of this study is to realize the partial non-magnetization via the Laser Directed Energy Deposition (L-DED) process. The impacts of applying the intermediate layer on the microstructure and magnetic properties were investigated when Fe-3Si was fabricated on the non-magnetic SUS316. The three types of boundary layers were identified in the sample fabricated without an intermediate layer: the ‘compositional boundary’, where the composition changes from the SUS316 part to the Fe-3Si part; the ‘phase boundary’ where BCC and FCC are mixed; and the ‘microstructural boundary’ consisting of fine grains. The application of Fe-4.5Si-1.2Al as the intermediate layer proved ineffective in suppressing the formation of the compositional boundary. Nevertheless, it was feasible to inhibit the formation of the phase and microstructural boundaries resulting in columnar grains comprising of a single BCC phase which were elongated parallel to the building direction. The magnetic domain structure of these columnar grains was observed using a Kerr microscopy, revealing that the grains oriented 〈001〉 to the direction of external magnetization exhibited superior domain change tendencies, similar to Fe-3Si area, despite the existence of the compositional boundary. These results indicated that the deterioration of magnetic properties can be suppressed by introducing an appropriate intermediate layer between the Fe-3Si and SUS316 sections.

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 89 (2025) 327–336. The captions of Table 3 and Fig. 5 were slightly modified.

Al–Zn–Mg alloys are age-hardenable aluminum alloys that achieve high strength through precipitation strengthening, making them widely used for structural components requiring a high specific strength. The Al–Zn–Mg alloys exhibit the greatest strengthening potential, primarily due to the formation of η and T phases. Micro-Vickers hardness measurements revealed that increasing the total (Zn + Mg) content enhances both the as-quenched and peak-aged hardness, while reducing the time to reach peak hardness. Tensile testing showed that higher (Zn + Mg) content increases ultimate tensile strength and proof stress but decreases ductility. The η′/η phases play a dominant role in strengthening compared with the T′/T phases. The mechanical properties of Al–Zn–Mg alloys are strongly influenced by microstructural features such as precipitate distribution, precipitate-free zone (PFZ) width, and grain size. Alloys with a higher precipitate number density and narrower PFZs generally exhibit higher strength but lower elongation. Achieving a microstructural condition that provides high hardness and tensile strength without sacrificing elongation is therefore essential for enhancing the overall mechanical performance of Al–Zn–Mg alloys.