Search Results (310)

The main objective of this paper is to present a comparative analysis between the finite element method (FEM) and artificial neural networks (ANNs) for predicting sheet metal springback, while addressing the “black-box” nature of machine learning through explainable AI (XAI). To achieve this novelty, a multi-layer perceptron (MLP) architecture was implemented and evaluated against numerical simulations during the bending of a hat-shaped profile. The experimental framework utilized dual-phase HCT600X steel (0.8 mm thickness), supplemented by deep-drawing DC06 and high-strength RAK40/70 steels to ensure dataset diversity and robust generalization capability. A key contribution of this work is the integration of local SHAP (Shapley additive explanations) analysis to interpret the ANN outputs, allowing for a precise quantification and rank ordering of how individual material, design, and process parameters govern the resulting springback angle. The developed MLP model (comprising two hidden layers with five neurons each) achieved high predictive fidelity, yielding an overall correlation coefficient R = 0.99074 alongside robust error metrics (RMSE and MAE). Full article

Corrosion of carbon steel components represents a major economic and safety challenge in industrial applications, motivating the development of protective thin film coatings with optimized deposition parameters. This study investigates the deposition of nickel nitride (Ni-N) thin films on AISI 1016 carbon steel and silicon (111) wafers by reactive radio-frequency (r.f.) magnetron sputtering at three power levels: 150, 175, and 200 W. Surface color, film thickness, roughness, crystal structure, mechanical properties, and electrochemical behavior were evaluated using optical microscopy, stylus profilometry, atomic force microscopy (AFM), X-ray diffraction (XRD), nanoindentation, and potentiodynamic polarization combined with electrochemical impedance spectroscopy (EIS). Increasing r.f.-power produced systematic surface color changes consistent with variations in film thickness, which ranged from approximately 25.0 to 50.7 nm. Higher deposition power promoted smoother surfaces, with average roughness (Ra) decreasing from 64.28 nm at 150 W to 20.62 nm at 200 W. XRD analysis revealed a monocrystalline Ni₃N hexagonal close-packed (HCP) phase at 150 W, transitioning to a dual-phase Ni₃N (HCP) and Ni₄N face-centered cubic (FCC) microstructure at 175 and 200 W. The highest hardness (11.80 ± 3.34 GPa) was recorded at 150 W, accompanied by pop-in events attributed to dislocation nucleation in the HCP lattice. Electrochemical evaluation in 3.5 wt.% NaCl solution demonstrated that films deposited at 150 and 175 W exhibited corrosion current densities and rates exceeding those of bare steel, confirming that these conditions accelerate rather than inhibit corrosion. Only the film deposited at 200 W achieved superior corrosion protection, with a corrosion current density and rate approximately 50% lower than bare steel, attributed to its denser microstructure and smoother surface morphology. These findings demonstrate that r.f. power is a critical parameter governing the properties of Ni-N thin films, and that careful optimization of deposition conditions is essential before recommending such coatings for industrial corrosion-protective applications. Full article

Corrosion of reinforcing steel and degradation of concrete caused by chloride penetration are the most critical forms of durability failure in marine environments. This requires that repair materials possess both high impermeability and stable chemical binding capacity. In this study, the impact patterns of sulfoaluminate cement (SAC) dosage on the chloride erosion durability of an OPC-GGBS-SAC ternary repair system were systematically evaluated. Through chloride ion binding capacity tests, electrical flux experiments, and microscopic analytical techniques including XRD, DTG and SEM-EDS, the synergistic regulation mechanisms of the dual functions of ‘physical barrier’ and ‘chemical binding’ in the composite material were elucidated. The findings show that the performance of the composite material was optimal at an SAC content of 10%. The electrical flux of composite materials at 28 d was 28.9% lower than that of the OPC system, whilst the chloride ion binding rate increased by 3.92%. Microstructural analysis indicates that an appropriate amount of SAC promoted the generation of ettringite (AFt) to optimize the early-age pore structure and stimulated the production of more C-S-H gel and AFm phases, thus synergistically enhancing impermeability and chemical binding capacity. When the SAC content exceeded 10%, excess gypsum inhibited the formation of AFm. Moreover, the concentration of early-stage hydration led to microdefects, resulting in a decline in durability. This study identifies the optimal dosage of SAC in the ternary system and clarifies the underlying mechanism, thereby providing a scientific basis for designing high-durability repair materials suitable for harsh ocean conditions. Full article

Metallographic microstructure analysis is essential for understanding the evolution of steel microstructures during heat treatment and mechanical processing. However, accurate analysis of optical micrographs remains difficult because of blurred grain boundaries, grayscale inhomogeneity within grains, and irregular grain morphologies. To address these issues, this work proposes an automated metallographic image-processing method based on superpixels, DPSS (dual-phase steel segmentation), with the main contribution focused on microstructure segmentation. First, image contrast and boundary visibility are enhanced by edge detection and sharpening. Then, superpixel segmentation is combined with extracted edge information to improve boundary localization and preserve irregular grain morphology, enabling more complete extraction of grain or particle regions from optical images. The proposed method is validated on optical micrographs of Mn-Si low-alloy steel, and the results show that it provides more accurate and complete segmentation than conventional ImageJ (Version: 1.54f)-based processing. Based on the segmented regions, a lightweight neural network is further used for phase identification. The final classification recognition accuracy can reach 99.91%. This classification result serves to demonstrate that the improved segmentation results can provide more reliable inputs for subsequent microstructure recognition. Overall, the proposed method offers an effective and automated solution for metallographic image segmentation and supports more accurate downstream phase analysis. Full article

To predict weld geometry and clarify structure–property relationships in high-speed coaxial dual-laser butt welding of 1 mm-thick SUS301 stainless steel sheets, an SSA-BP neural network model was established to describe the nonlinear correlation between welding parameters and weld morphology. The model related continuous laser power, welding speed, pulse frequency, and pulse width to weld width and penetration depth. To improve the transparency of model validation, conventional BP and SSA-BP models were compared using the same independent test set, and five-fold cross-validation was performed using the original experimental samples. On the independent test set, the SSA-BP model achieved an overall correlation coefficient of R = 0.960, with RMSE values of 0.0561 mm and 0.0439 mm for weld width and penetration depth, respectively. Compared with the conventional BP model, SSA-BP reduced the overall RMSE, MAE, and MAPE by 25.9%, 36.4%, and 29.6%, respectively. The five-fold cross-validation further indicated stable prediction performance under different data partitions. Based on the predicted and experimentally measured weld geometry, candidate parameter sets were screened according to the weld aspect ratio (Φ = h/w). Within the present experimental window, joints with Φ = 0.82–0.84 showed more stable weld formation and relatively higher ultimate tensile strength (1211.4–1264.8 MPa) than two representative joints outside this interval (796.0 MPa at Φ = 0.63 and 1061.1 MPa at Φ = 0.88). Therefore, this interval should be regarded as a favorable empirical range under the present welding conditions rather than a universal optimum. Fractographic observations of a representative high-strength joint showed abundant dimples and tear ridges, indicating ductile fracture characteristics. EBSD analysis further revealed a graded microstructure from the weld center to the base metal. The weld center and fusion line-adjacent regions exhibited relatively high fractions of high-angle grain boundaries (66.2–70.6%), while phase distribution, GND density, and KAM maps indicated a gradual phase transition and localized but non-continuous strain concentration features across the joint. These results indicate that the present approach provides an effective route for weld geometry prediction and for linking morphology screening with tensile response and microstructural heterogeneity in SUS301 thin sheet welding. Full article

The present study employed molecular dynamics (MD) simulations to investigate the deformation behavior of a ferrite/cementite (α-Fe/Fe₃C) dual-phase system under ultra-high strain rate conditions. A systematic examination was conducted to investigate the effects of deformation temperature and loading direction (LD-I: loading on the ferrite side; LD-II: loading on the cementite side) on the mechanical properties, microstructural evolution, and strain transfer of the system. The results show that both the tensile strength and the maximum uniform plastic strain (plasticity) exhibit a non-monotonic variation with increasing temperature, first increasing and then decreasing, with the optimal strength-ductility synergy achieved. At the same deformation temperature, the strength and plasticity of the system under LD-I are significantly superior to those under LD-II conditions. The observed differences in mechanical properties are attributed to alterations in strain-transfer uniformity, atomic rearrangement activity, and crack-nucleation sites induced by temperature and loading direction. This study provides mechanistic insights into the dynamic failure of pearlitic steels under extreme conditions. These atomistic mechanisms can serve as a reference for multiscale modeling or for interpreting experiments under comparable dynamic loading. Full article

The corrosion behavior and time-dependent mechanism of 22MnB5 steel featuring a thinned Al-Si coating (60 g/m²) were systematically investigated in a chloride ion wet–dry cyclic environment, motivated by the demand for thinning and toughening development of aluminum-silicon coatings. A periodic immersion accelerated corrosion test using 3.5% NaCl solution was conducted, together with macro/microscopic morphology observation (SEM/EDS), phase analysis (XRD, FTIR), and electrochemical measurements (polarization curves, EIS). The Al-Si coated steel was studied over corrosion periods of 1, 8, 10, and 20 days to elucidate its corrosion behavior, interfacial evolution, and failure mechanism. The results indicated that the corrosion process exhibited a three-stage evolution: stable protection, rapid failure, and dynamic equilibrium. At the initial stage (1 day), a dense Al₂O₃ passive film formed on the coating surface, providing excellent substrate protection, with a corrosion current density of only 1.77 µA/cm² and a maximum charge-transfer resistance (R₂) of 652 Ω·cm². In the middle stage (8 days), Cl⁻ permeated through the cracked film, triggering selective dissolution of Al, while Si was enriched in situ to form a porous residual layer; the corrosion current density (I_corr) sharply increased to 13.25 µA/cm², and R₂ dropped to its minimum of 156.6 Ω·cm². Corrosion products at this stage were mainly Al₂O₃ and SiO₂, accompanied by small amounts of iron oxyhydroxides and hydroxides, and local coating failure began to appear. During the later stage (10–20 days), the corrosion products evolved into γ-FeOOH, α-FeOOH, and Fe₂O₃, which, together with an amorphous SiO₂ gel network enriched at the interface, formed a dual-layer composite rust layer. R2 consequently recovered from 156.6 Ω·cm² at 8 days to 424 Ω·cm² at 20 days, indicating a reduced corrosion rate and entry into a stable inhibition stage. The critical failure mechanism is that Cl⁻ preferentially penetrates the surface of the Al₂O₃ passive film, disrupting the metastable state of the coating and thereby creating pathways for corrosive media intrusion. The findings of this study can provide technical support for the safe application of such as-received coatings in non-load-bearing components with heat and corrosion resistance requirements. Full article

This study utilized a twisted wire rotating arc cladding method to in situ fabricate a Fe-containing multi-principal element alloy (HPEA) coating derived from NiCrCoTiMo stranded wire on 45 steel (equivalent to AISI 1045 steel). The macroscopic morphology, microstructure, mechanical properties, and electrochemical corrosion behavior of the prepared coatings were examined. The coating exhibited no visible cracks or pores and displayed a dual-phase face-centered cubic (FCC) + body-centered cubic (BCC) structure, with an average grain size of 78 μm for the FCC phase and 1 μm for the BCC phase. The microhardness of the coating is approximately 381.3 HV_0.1. Compared to 45 steel, the coating’s coefficient of friction (COF) decreased from 0.6265 to 0.5125, representing an 18.2% reduction. The calculated wear rate of the coating was 1.47 × 10⁻⁵ mm³/N·m, approximately six times lower than that of 45 steel (8.93 × 10⁻⁵ mm³/N·m). Electrochemical testing revealed that the coating’s open-circuit potential (OCP) was −0.405 V vs. the saturated calomel electrode (SCE), with a corrosion potential (E_corr) of −0.556 V vs. SCE and a corrosion current density (I_corr) of 4.458 × 10⁻⁶ A/cm². In comparison, 45 steel exhibited an OCP of −0.582 V vs. SCE, with corrosion parameters of E_corr = −0.840 V vs. SCE and I_corr = 1.302 × 10⁻⁵ A/cm². These results demonstrate the superior corrosion resistance and wear performance of the coating, underscoring its potential for applications in challenging environments that demand enhanced material durability. Full article

Wire Arc Additive Manufacturing (WAAM) has emerged as a promising additive manufacturing technique due to its high deposition rate and low material cost. WAAM is increasingly adopted in various industries for the production of large-scale metal components, yet optimizing productivity without sacrificing mechanical integrity remains a critical challenge, particularly for low-carbon steels. This study systematically investigates the influence of key WAAM parameters—welding current (100–350 A) and travel speed (5–30 mm/s) on the deposition stability, microstructure, and mechanical properties of thin walls made of low-carbon Fe–0.09 C–1.10 Cr–1.47 Mn–0.59 Si–0.56 Mo–0.11 Ni–0.23 V steel. A stable processing window for defect-free wall fabrication was established for currents of 100–250 A, while higher currents of 300–350 A resulted in melt pool instability and geometrical distortions due to excessive heat input. Microstructural characterization revealed a dual-phase structure consisting of allotriomorphic ferrite (ALF) and acicular ferrite (AF) in all samples. The microstructural evolution was critically governed by variations in the cooling time in the critical temperature range of 800 °C to 500 °C (t_8/5) within the thermal cycles, a direct consequence of the heat input quantified through volumetric energy density. Low heat input at 100 A, 5 mm/s promoted a microstructure with minimal ALF fraction of ~10%, whereas high heat input at 350 A, 30 mm/s induced significant ferrite recrystallization and coarsening, increasing ALF fraction to ~55%. These microstructural changes directly affected mechanical properties: YS/UTS decreased from 512 MPa/668 MPa to 401 MPa/602 MPa, respectively. Concurrently, the deposition rate increased substantially from ~1.6 kg/h to ~6.3 kg/h. The results demonstrate a critical trade-off between productivity and mechanical performance, providing a practical framework for parameter selection in WAAM-fabricated low-carbon steel components. Full article

Although 45 steel is widely used in the manufacture of mechanical parts, its application in harsh working conditions is limited owing to its low hardness, poor wear resistance, and corrosion resistance. Laser cladding can enhance the performance of the working surface without sacrificing substrate toughness. CoCuNiTi HEACs with different cBN additions were successfully prepared on a 45-steel substrate. The phase structure, microstructure, elemental composition, wear, and corrosion behavior of CoCuNiTi + x cBN (x = 0.0, 0.5, and 1.0 wt.%) HEACs were investigated using XRD, OM, SEM, EDS, friction and wear tester, and electrochemical workstation, respectively. The results show that all three coatings exhibit a dual-phase structure composed of FCC and BCC phases. The addition of cBN transforms the alloy phase structure from the original FCC main phase to the BCC main phase. The incorporation of cBN significantly reduces the lattice constant and cell volume of the alloy phase. The change in the alloy phase density is negatively correlated with the cell volume. CoCuNiTi + x cBN (x = 0.0, 0.5, and 1.0 wt.%) alloys have a dendritic structure. No pores were observed in the cBN-containing sample. The content of Ti in the primary phase is the highest. Co is enriched in the dendrite region, and Cu is enriched in the interdendrite region. The significant reduction in the average segregation coefficient for cBN-containing samples is attributed to the heterogeneous nucleation of the alloy melt at lower undercooling levels and the significant increase in the diffusion rate. The friction coefficient of the alloy decreases significantly with increasing cBN content. The sample with 1.0 wt.% cBN shows the best wear resistance, mainly due to the combined effects of hard particle support, solid solution strengthening, phase interface reduction, and high thermal conductivity of cBN. The sample with 1.0 wt.% cBN has the largest capacitive arc radius and charge-transfer resistance, along with the lowest annual corrosion rate, indicating optimal corrosion resistance. This is primarily related to the reduction in pore defects caused by cBN addition, hindrance of uniform penetration of the corrosive medium by dispersed cBN particles, and increased complexity of the anodic dissolution process. CoCuNiTi HEACs reinforced by cBN can simultaneously improve the wear and corrosion resistance of the surface of the 45-steel substrate, providing a feasible strategy for the design of high-performance protective coatings. Full article

The combination of elevated temperature and tribo-corrosion leads to the accelerated degradation of structural components used in many extreme environments. Recently developed high-entropy alloys (HEAs) with multiple principal elements have the potential for superior degradation resistance compared with presently used structural alloys. Here, we demonstrate the microstructural stability, pitting resistance, and superior tribo-corrosion degradation resistance of the AlCoCrFeNi_2.1 eutectic HEA in comparison with duplex stainless steel 2205 in deionized water (controlled low-ionic-strength electrolyte) at 25 °C, 50 °C and 100 °C. The AlCoCrFeNi_2.1 HEA showed excellent microstructural stability and tribo-corrosion resistance at all three temperatures, an order-of-magnitude lower wear rate, and a lower coefficient of friction compared with duplex 2205 steel. The lowest wear volume loss and wear rate for both AlCoCrFeNi_2.1 and duplex steel were recorded at 50 °C, which was attributed to temperature-assisted passivation and formation of a comparatively stable tribological surface condition. These results suggest superior performance of eutectic HEAs in tribo-corrosion applications compared with currently used dual-phase steels and motivate future evaluation in ion-containing industrial water chemistries. Full article

In the automotive industry, the most critical factor affecting dimensional stability during the forming of Advanced High-Strength Steels (AHSSs) is the springback phenomenon. This study systematically investigates the springback behavior of four distinct dual-phase steel grades (DP450, DP600, DP800, and DP1000) in U-shaped body-in-white (BIW) structures across 180 distinct scenarios. The experimental design varied sheet thicknesses (1.2, 1.6, 2 mm), die clearance angles (5°, 10°, 15°), and bending radii (R6, R8, R10, R12, R14). Numerical simulations using Autoform R8 were validated against Atos 3D optical scanning data, achieving values exceeding 0.90 for all grades. Quantitative validation metrics showed exceptional fidelity for lower-strength grades with error margins below 1.1%, while the maximum deviation was limited to 3.1% for the ultra-high-strength DP1000 grade. The findings demonstrate that while increasing material strength substantially intensifies springback, the strategic augmentation of sheet thickness and optimization of die radius effectively mitigate these deviations, thereby enhancing process stability. Full article

Life cycle greenhouse gas (GHG) accounting is increasingly required to substantiate the climate value of wind power beyond “zero-emission” operation, especially under China’s dual-carbon targets. Robust estimation of life cycle GHG emission intensity and the identification of actionable mitigation levers are therefore important for credible transition planning. In this study, a process-based life cycle assessment (LCA) was conducted for a representative 100 MW onshore wind farm in Gaoyou, Jiangsu Province, China, following ISO 14040/14044. To enhance engineering relevance, the construction and installation phase was modeled in a refined manner by decomposing it into road, wind-turbine, booster-station, and transmission-line engineering and further into unit processes. The results show that the overall life cycle GHG emission intensity of the studied wind farm is 24.6 g CO₂-eq/kWh. Scenario analysis further indicates that reducing curtailment and improving end-of-life recycling are effective pathways to lower emission intensity, while the net advantage of hybrid versus steel towers depends on recycling performance when end-of-life credits are included. The study also summarizes practical implications for low-carbon equipment/material procurement and green supply-chain governance, low-carbon construction and logistics, coordinated “source–grid–load–storage” planning to curb curtailment, and more standardized and comparable life cycle carbon accounting for wind projects in China. Full article

In this study, Sn and Ni powders were incorporated into the flux core of brass brazing filler metals, with alloying achieved via in situ synthesis during brazing. The effects of Sn/Ni single and composite additions on the microstructure, melting characteristics, wettability on Q235 steel, and tensile strength of corresponding brazed joints were systematically investigated. Sn addition increased the β-phase fraction, reduced the solidus temperature, and significantly improved wettability—with a maximum unit spreading area of 4.22 mm²/mg at 20 wt.% Sn (2.85 times that of the Sn/Ni-free baseline). However, coarse β-phase grains and their transformation to brittle β′-phase at room temperature resulted in no enhancement of joint tensile strength. Ni addition expanded the α-phase region, refined grains, and induced solid solution strengthening of the α-phase matrix; joint tensile strength peaked at 501 MPa at 20 wt.% Ni (65% higher than the baseline). Excessive Ni (≥40 wt.%) deteriorated wettability due to reduced molten superheat, and 50 wt.% Ni caused α-phase over-strengthening and embrittlement, leading to a sharp strength drop to 214 MPa. The composite addition of 3 wt.% Sn + 10 wt.% Ni reconstructed the filler metal into a refined, uniform grid-like (α + β) dual-phase structure without new phase formation, realizing synergistic optimization of wettability and mechanical properties. The co-added sample exhibited optimal performance, with a unit spreading area of 4.51 mm²/mg and joint tensile strength of 584 MPa (206% and 93% higher than the baseline, respectively). This improvement was attributed to the coupling of uniform stress dispersion by the grid-like microstructure and dual-element functional complementation (Sn for wettability and β-phase strengthening; Ni for grain refinement and α-phase strengthening). This work provides a feasible alloying modification strategy for brass flux-cored brazing filler metals, and the revealed microstructure-performance regulation mechanism offers a valuable reference for developing high-performance brass brazing filler metals. Full article

In the current numerical simulation study of high-strength steel welding, ignoring the phase transformation plasticity effect in the coupling analysis led to a significant deviation between the simulated value of residual stress and the experimentally measured value. To investigate the influence mechanism of the Welding Residual Stresses (WRSs) of 30MnCrNiMo armor steel, the transformation plasticity (TP) coefficient (7.81 × 10⁻⁵ MPa⁻¹) was measured via a Gleeble 3500, and a Finite Element Model (FEM) of thermal–metallurgical–mechanical coupling considering yield strength, volumetric strain and TP behavior in Solid-State Phase Transformation (SSPT) was developed. The results show that the volume expansion during the SSPT is the main factor for the shift in WRS from tensile to compressive. In contrast, the TP effect reduces the peak longitudinal tensile stress in the Heat-Affected Zone (HAZ) by 51 MPa. It also ultimately neutralizes the compressive component in this region. When the martensite fraction ranges from 0.12 to 0.45, transformation plastic strain becomes the dominant factor, leading to a characteristic evolution of longitudinal stress that initially decreases and subsequently increases. The FEM incorporating the TP effect successfully captures the dual reversals of residual stress in the HAZ. The average relative error between the simulated longitudinal stress and the experimental data obtained via X-ray diffraction (cosα method) is 8.8%. The TP coefficient database and the developed multi-field coupling model markedly enhance the predictive accuracy for WRS in 30MnCrNiMo steel, offering a robust theoretical foundation for the design of stress corrosion resistance and the service life assessment of welded joints in armored vehicles. Full article