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. [doi:10.2320/matertrans.MT-MA2026009]
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 degrees C, unlike oxidation under atmospheric pressure, Cu2O films with a particle size of approximately 5 & micro;m 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 degrees 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. [doi:10.2320/matertrans.MT-D2025014]
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 & micro;m 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 & micro;m was introduced in the radial direction at the punch edge, and an additional chamfer of 1-2 & micro;m 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. [doi:10.2320/matertrans.MT-MA2026016]
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.
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. [doi:10.2320/matertrans.MT-MA2026006]
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 HV0.1) 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. [doi:10.2320/matertrans.MT-D2026001]
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 socalled "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.
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 alpha-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 alpha-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 alpha-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.
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 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.
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. [doi:10.2320/matertrans.MT-MA2026008]
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.
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 degrees C and 0.1-1.0 s11. 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.
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 degrees 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 degrees C and strain rates of 0.1-1.0 s11revealed a pronounced reduction in flow stress and enhancement in ductility relative to room-temperature forming. An optimal forming window was identified at 160 degrees C and 0.5 s11, 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. [doi:10.2320/matertrans.MT-MA2026017]
