The increasing demand for ultra-precision components with complex surface geometries has stimulated the development of advanced deterministic polishing technologies. This investigation explores the impact of external vibration on the rheological properties of polishing slurry and the material removal performance during the vibration-assisted force rheological polishing (VFRP) process. The mechanical response of the vibrating workpiece surface under various vibration conditions was numerically analyzed using ANSYS Fluent 14.5. The results demonstrated a strong correlation between the surface pressure imposed on the workpiece and the applied vibration amplitude as well as vibration frequency. Experimental results validate that the introduction of vibration promotes a reversible rheological transition of the slurry from a fluid-predominant state to a solid-resembling structure, which facilitates abrasive particle confinement and subsequently enhances polishing capability. The reliance of stainless-steel sheet polishing performance on vibration parameters was evaluated. With the optimized combination of polishing speed (40 rpm), vibration frequency (80 Hz), and amplitude (0.35 mm), the 30 min polishing process yielded a material removal rate of 68.1 nm/min and reduced the average surface roughness (Sa) from 80 nm to 7.1 nm. The acquired results provide constructive direction for optimizing the VFRP process and promoting its application in high-efficiency, ultra-precision surface polishing.
Super-gravity technology was applied during the solidification of high-conductivity No. 2 oxygen-free copper (TU2) to achieve synergistic optimization of its electrical and mechanical properties. Theoretically, super-gravity promoted grain refinement by increasing the nucleation rate (via dendrite fragmentation and enhanced heterogeneous nucleation) and reducing the grain growth rate (due to increased melt viscosity). Experimentally, applying the super-gravity field specifically during solidification proved essential for effective microstructural modification. As the gravity coefficient (G) increased from 1 to 1000, grain size was significantly refined, especially when G > 500. Consequently, Vickers hardness increased from 59 to 95 kg/mm2 and ultimate tensile strength rose from 112.2 to 124.7 MPa, while electrical conductivity remained nearly unchanged (from 106.92% to 106.38% IACS). The slight initial increase in conductivity was attributed to reduced porosity, followed by a minor decrease due to enhanced grain boundary scattering. This study demonstrated that super-gravity solidification was an effective strategy for fabricating high-conductivity metallic materials with simultaneously improved strength and hardness.
Quasi in situ observations of the early stage of secondary recrystallization in Fe-3.25 wt.% Si high-permeability grain-oriented silicon steel indicate that large matrix grains locally impede the migration of secondary recrystallized grain boundaries. A critical grain-size criterion for identifying potential pinning grains is proposed, and a kinetic model incorporating the matrix grain-size distribution is developed. For the abnormal grain tracked at 1000 °C, the measured grain-size increment over 100 s was approximately 60 μm; the proposed pinning model predicted 47 μm, whereas the weighted-average model predicted 171 μm. Model calculations further suggest that matrix grain-size dispersion, pinning force, grain size, and relative grain-boundary energy jointly affect the early-stage growth of Goss grains. These results provide a framework for interpreting early secondary-recrystallization kinetics, while broader experimental validation is still required before the predicted parameter combinations can be used for process control.
Industrial pure copper sheets as a crucial electronic material have currently attracted extensive attention from scholars due to the rapid development of the information technology industry. However, past investigations into the regulation discipline of the microstructure and mechanical properties of pure copper have not paid sufficient attention due to the inevitably low strength induced by the lack of alloying elements. In this study, a typical T2 copper sheet was fabricated by a severe cold-rolling process with a deformation amount of 83% followed by different annealing temperatures ranging from 200 to 500 °C, and the influence of annealing temperature on the evolution of microstructure, mechanical and physical properties and crystallographic orientation (CRO) was investigated systematically. The microstructure features and micro-texture of the studied T2 copper sheet were characterized by optical microscopy (OM) and scanning electron microscopy equipped with electron back-scattered diffraction (EBSD) techniques throughout the entire process from the initial state to the deformed state and annealed state, and the tensile property and electrical conductivity were tested by utilizing a universal testing machine and a digital micro-ohmmeter. Results indicate that the yield strength and tensile strength of the studied T2 copper sheet are both decreased with increasing annealing temperature, accompanied by an increase in electrical conductivity, and the maximum conductivity of up to 98.2% IACS can be reached at the annealing temperature of 500 °C. With the increase in annealing temperature, the degree of recrystallization becomes increasingly sufficient, and the volume fraction of recrystallized grains is increased from ~17.8% to ~35.7% with the annealing temperature increased from 200 to 500 °C. The texture component of the studied T2 copper sheet processed by severe cold rolling with a deformation amount of 83% is characterized by a deformation texture composed of copper texture and S texture, and is then transformed into a texture that predominantly consists of Cube texture under the application of annealing treatment, and the maximum intensity value of Cube texture is enhanced with the increase in annealing temperature.
This paper presents the results of a study on the utilization of chromium-containing waste in the production of mineral wool based on natural basalt. It was shown that a mixture of low-dolomite chromate sludge and low-carbon ferrochrome slag in a 1:1 ratio is compositionally close to dolomite. When dolomite is equivalently replaced in the mineral wool batch, the physicochemical characteristics of the melt remain suitable for mineral wool production. The complete reduction of iron and chromium oxides is achieved in the presence of carbon, resulting in their transfer to the metallic phase, where iron and chromium cations are present in the form of carbides. Due to the cost difference between chromium waste and dolomite, implementing the proposed technology makes it possible to significantly improve the efficiency of chromium waste utilization by reducing the production cost of mineral wool. The Aktobe region has all the prerequisites for implementing the developed technology, with active sources of chromium-containing waste pollution (ACCP, AFP) and basalt deposits, as well as the operational experience of the mineral-wool-manufacturing enterprise Basalt-A LLP.
1D hollow Ni/C microtubes with tunable carbon shell coating were fabricated through a three-step method with carbon fiber templating, polydopamine coating and carbothermal reduction. The competitive behavior between NiO reduction and Ni-catalyzed graphitization dominates the evolution of carbon structure and interface state. Adjusting dopamine content achieves the dielectric polarization mode evolution from NiO/Ni Schottky junction to Ni/C interfacial and intrinsic dipole polarization, realizing band-tunable microwave absorption. With favorable modulation of the carbon shell, the absorber thickness required for efficient absorption declines substantially, while the absorbing bands shift from the X-Ku boundary toward high-frequency Ku and low-frequency S-C band. NC-3 with the thickest carbon coating delivers the strongest absorption of −49.58 dB at merely 1 mm, and its absorbing band can also be tuned to the S band at 6.6 mm. This work offers a concise interfacial strategy for lightweight and band-tunable microwave absorbers.
Molybdenum (Mo), owing to its excellent high-temperature resistance and low sputtering yield, is widely used in advanced equipment such as extreme ultraviolet (EUV) lithography systems. To meet the demand for regulating the surface wettability of Mo, this study employs micromilling to fabricate microgroove arrays on Mo surfaces to enhance their hydrophobicity. First, comparative micromilling experiments are conducted under flood cooling and minimum quantity cooling lubrication (MQCL) conditions. The effects of process parameters, including axial depth of cut (ap), spindle speed (n), and feed per tooth (fz), on burr height (H) are investigated under the two cooling/lubrication conditions. The results show that the burr heights obtained under flood cooling are generally lower than those obtained under MQCL. Subsequently, the machining parameters under flood cooling are evaluated using an orthogonal experimental design. A mathematical model relating the microgroove array geometry to the contact angle is then established based on Gibbs free energy to guide the design of surface microgroove structures. Finally, microgroove arrays are fabricated on Mo surfaces using the preferred machining parameters. The results demonstrate that the microgroove arrays effectively enhance the water hydrophobicity of the Mo surface. The static water contact angle increases from 62.45 ± 0.25° for the untreated Mo surface to a maximum of 128.50 ± 0.12°, thereby achieving a transition from hydrophilic to hydrophobic behavior.
As manufacturers seek to improve cutting process sustainability, alternative metalworking fluid (MWF) strategies are increasingly being explored. For the first time, this study characterises tool wear when shoulder milling both Grade 5 titanium (Ti-6Al-4V) and Grade 2 commercially pure titanium (CP-Ti) with a novel through-spindle Aurion Machining Technologies ionised air (IA) MWF setup. Preliminary results show that during CP-Ti milling trials, the IA strategy led to a tool life of between 85% and 91% of that which was achieved with soluble oil emulsion MWF, whilst during Ti-6Al-4V milling the observed tool life with IA was between 158% and 278% greater than with emulsion coolant at analogous cutting conditions (2.58 and 3.78 times respectively). In addition, IA generated a 26.2% reduction in surface roughness after Ti-6Al-4V milling, potentially indicating a change in tool–surface interaction behaviour. These benefits are compounded as IA returns to its original condition rapidly after utilisation, meaning low environmental and health impact with no waste MWF liquids/gases/mist, clean metal cuttings and low delivery power. Beyond these promising results, cooled and dried but non-ionised air was also shown to perform strongly (regarding tool wear in Ti-6Al-4V milling), relative to emulsion MWF, such that at 190 m/min cutting speed it generated 90% of the tool life which was achieved by the IA strategy. Whilst these preliminary findings require confirmation through repeat testing, IA remains of clear interest for further experimental investigation across a range of subtractive processes. Moreover, this work highlights the potential benefits, niches and configurations for air-based MWFs in general, with further mechanistic and tribological exploration warranted.
Zn-Al-Mg (ZAM) coatings have attracted significant attention in the field of corrosion protection owing to their combination of excellent corrosion resistance and cost-effectiveness. However, the corrosion behavior of ZAM coatings was governed by the synergistic coupling effects of multiple factors, including alloy composition, coating thickness, corrosive medium, and multiphase microstructure, making it challenging for traditional empirical analysis to systematically reveal the underlying mechanisms. To address this challenge, we constructed a multidimensional corrosion dataset comprising alloy composition, corrosive medium, coating thickness, and phase composition, based on literature data from the past three decades combined with self-measured potentiodynamic polarization experimental results. After data normalization and correlation analysis, we introduced phase structure features—including the Al-rich phase, MgZn2 phase, Mg2Si phase, and eutectic microstructures—to enhance the model’s capability in representing microstructural factors. On this basis, we established random forest (RF), support vector regression (SVR), and artificial neural network (ANN) models to predict the corrosion current density, and subsequently conducted an interpretability analysis using the SHapley Additive exPlanations (SHAP) method. The results demonstrated that the expanded feature set significantly improved the prediction performance of the models. Among them, the RF model exhibited the best performance, achieving a determination coefficient (R2) of 0.7363 on the test set, which represented a substantial improvement over the baseline dataset. Feature importance analysis revealed that coating thickness, Mg content, NaCl concentration, and Zn content were the primary factors influencing the corrosion current density. Further SHAP analysis showed that the marginal contribution of the eutectic phase was more prominent in local samples. Meanwhile, the Mg element exhibited distinct non-linear regulation characteristics, exerting varying impacts on the corrosion behavior across different concentration ranges. This study demonstrated that the interpretable machine learning models constructed via feature engineering not only improved the prediction accuracy of the corrosion performance of ZAM coatings, but also provided a novel data-driven approach to revealing the intrinsic correlations among alloy composition, phase structure, and corrosion response.
The tribological performance of copper-matrix sintered brake pads for high-speed rail applications is strongly influenced by ceramic reinforcement type. However, a systematic comparison of SiC, ZrO2, and SiO2 within Cu and Cu–Bronze (Cu–Br) matrix systems remains limited. In this study, six powder metallurgy composites were produced by cold pressing and sintering at 900 °C, with each matrix reinforced with 2 wt.% SiC, ZrO2, or SiO2 and containing graphite and MoS2 as solid lubricants. Tribological tests were performed at 25, 100, and 400 °C under an 18 N normal load. Microstructural and thermal characteristics were evaluated using optical microscopy, SEM/EDS, and DTA/TGA. The coefficient of friction (COF) ranged from 0.163 to 0.364 across all formulations and temperatures. The Cu–Br-based composites exhibited a narrower reinforcement-dependent COF range than the Cu-based composites, particularly at elevated temperatures. Cu–SiO2 showed the highest COF within the Cu-based at all test temperatures, whereas Cu–Br–SiC composite exhibited the highest COF among the Cu–Br-based composites at 400 °C. The lowest specific wear rates were obtained for Cu–SiO2 at 25 °C and Cu–SiC at 400 °C. SiC-reinforced composites exhibited the highest hardness within both matrix systems.
Cold-roll-bonded (CRB) Fe–Al clad sheets, which incorporate an internal steel layer within the clad structure, are candidate materials for dissimilar joining in lightweight structural applications, yet systematic comparisons of their weldability across multiple joining processes remain limited. This study evaluates the process-dependent weldability of CRB Fe–Al clad sheets using three joining processes: laser lap welding, DC resistance spot welding, and cold metal transfer-pulse (CMT-P) arc welding. Weld appearance, cross-sectional morphology, tensile shear behavior, and fracture characteristics were assessed for multiple sheet configurations and clad-layer thicknesses. Across all three processes, configurations that placed the clad sheet directly toward the heat source were prone to cracking or strength degradation when the internal steel layer melted extensively, whereas limiting steel-layer involvement produced more stable joints. Among the three processes, resistance spot welding provided the widest workable process window, while laser and CMT-P arc welding achieved peak strengths only within a narrow heat-input range. These findings indicate that the role of the internal steel layer is process-dependent and provide practical guidance for sheet configuration and parameter selection when joining CRB Fe–Al clad sheets to steel or aluminum components.
Additive manufacturing offers a novel technical route for the fabrication of complex lightweight aluminum alloy components in the aerospace field. However, high-strength aluminum alloys still suffer from defects such as hot cracking, porosity and microstructural inhomogeneity during the forming process. Particle reinforcement is a critical strategy to enhance the properties of additively manufactured aluminum matrix composites. Focusing on three mainstream processes, namely powder bed fusion–laser beam (PBF-LB), directed energy deposition–arc (DED-Arc) and directed energy deposition–laser beam (DED-LB), this paper elaborates on the roles of typical reinforcement particles including TiB2, TiC, SiC and CaB6 in microstructure tailoring, defect suppression and property enhancement. It further compares the three processes in terms of forming characteristics, microstructure evolution and aerospace applications. Finally, key challenges including particle dispersion, interfacial stability, process consistency and engineering application are summarized, and corresponding future development prospects are discussed.
The initiation of electrochemical corrosion on steel surfaces begins with water molecule aggregation, though the atomic-scale mechanisms from adsorption and wetting to corrosive microdroplet formation remain unclear. Using molecular dynamics simulations, this work investigates the formation of corrosive aqueous micro-environments on iron-based surfaces during early condensation. It focuses on the regulatory effects of surface roughness and local hydrophilic sites on condensation nucleation, droplet growth, and wetting. Results show a linear correlation between droplet contact angle and solid–liquid interaction energy, with temperature dependence controlled by the substrate’s intrinsic wettability. For fence-type rough surfaces, we clarify the transition from a critical to a mixed (Cassie–Wenzel) wetting state, confirming that roughness enhances intrinsic wettability. Condensation analysis reveals that stronger solid–liquid interaction promotes water adsorption and induces a shift from dropwise to filmwise condensation, with interphase temperature difference driving heat transfer. On hydrophobic surfaces with local hydrophilic sites, these sites serve as preferential nucleation points. Their size effect can pin the three-phase contact line, leading to droplet growth in a high-contact-angle mode. This study offers an atomic-scale view of how condensation creates the initial aqueous environment required for electrochemical corrosion, providing theoretical insight into phase-change heat transfer and interfacial behaviour on complex surfaces. The findings guide the design of surfaces resistant to condensation-induced corrosion.
Post-weld cold rolling and subsequent annealing were applied to friction-stir-welded Al/Cu joints to examine their interfacial evolution, tensile behavior, and local cupping response. Multi-pass cold rolling reduced the sheet thickness from 3.0 to 0.4 mm and transformed the initially inclined Al/Cu interface into a near-horizontal laminated structure with an average inclination of 3.97° relative to the sheet plane. Rolling fragmented and thinned the interfacial reaction layer (narrow nanoscale reaction-product layer) and increased the average tensile strength from 99 to 370 MPa, whereas the elongation remained low at approximately 0.6%. Annealing at 300 °C for 30 min promoted recovery and recrystallization, reduced the hardness difference across the joint, and increased the elongation to 8.8%, with an average tensile strength of 182 MPa. The macroscopic tensile fracture path changed from the Al/Cu interfacial region (broad transition zone) in the as-welded joint to the laminated region (rolled interfacial region characterized by alternating Al-rich/Cu-rich lamellae) after rolling and annealing. In contrast, interface-centered cupping specimens exhibited a lower load-carrying capacity and cracking along the interfacial region. These results show that post-weld rolling and annealing improve the uniaxial tensile response through interface flattening and microstructural homogenization, while the interfacial region remains susceptible to cracking during combined stretching and bending deformation.
Aluminum and its alloys feature low weight and high strength. They are widely applied in aerospace, automobile manufacturing, and marine engineering. However, they are highly susceptible to localized corrosion. Such defects can severely restrict the service life of the substrate materials. Pristine graphene exhibits atomic-level compact impermeability, stable chemical inertness, and excellent mechanical properties. It is a promising candidate material for the protection of aluminum substrates. Nevertheless, an electrically insulating interlayer is generally required between pristine graphene and aluminum to achieve reliable protection. This measure avoids the risk of galvanic corrosion. This paper systematically reviews the latest research progress of graphene-based coatings on aluminum, focusing on pristine graphene, graphene oxide (GO), reduced graphene oxide (rGO), and graphene-polymer composite coatings. It focuses on the preparation methods and corrosion protection performance of the materials. This study compares various mainstream preparation technologies in detail. The technologies include chemical vapor deposition, electrochemical deposition, mechanical exfoliation, solution coating, laser induction, and thermal spraying. The corrosion protection mechanism is discussed from three dimensions. The dimensions include physical barrier effect, tortuous path mechanism, and electrochemical protection. Key influencing factors, such as coating defects and environmental conditions, are also investigated. This paper summarizes the application potential of graphene-based coated aluminum in high-end manufacturing fields. It points out the major existing challenges of the material. The challenges involve coating uniformity, adhesion strength, long-term stability, and industrial production. Finally, future research directions are proposed in this work. These directions include the development of innovative coating technologies, the construction of composite protection systems, the design of intelligent self-healing functions, and the exploration of environmentally friendly preparation processes.
Metal additive manufacturing (AM) enables compact hydraulic manifolds with curved internal channels, reduced part count and integrated functionality. However, these benefits also create major inspection challenges, especially in thick metallic sections containing closely spaced and intersecting passages. This study examines the practical use of X-ray computed tomography (CT) for an industrial hydraulic manifold manufactured from maraging steel MS1 by laser powder bed fusion (LPBF). Selected cross-sections from the reconstructed CT volume were compared with the nominal computer-aided design (CAD) geometry and evaluated using a qualitative interpretability classification supported by comparative image contrast-to-noise ratio (CNR) analysis and approximate projected steel thicknesses. Clearly interpretable regions showed higher and more consistent CNR, whereas geometrically congested regions generally exhibited lower and more variable local contrast. However, projected material thickness alone did not determine interpretability, indicating an additional influence of geometric overlap, orientation and reconstruction artefacts. Particular attention was given to a channel wall adjacent to a locally collapsed external support structure. No spatially persistent through-wall discontinuity was identified, although smaller defects, local wall thinning and metallurgical changes could not be excluded. A pneumatic immersion test at 0.8 MPa showed no visible bubble formation or observable pressure decrease. This pressure exceeded the expected operating pressure of the affected relief or tank channel but was substantially below the 35 MPa maximum intended pressure of the pressure-side circuits and therefore did not constitute structural qualification. The study demonstrates that whole-component CT can provide useful local inspection information for complex LPBF manifolds, but its reliability depends strongly on local geometry and acquisition conditions. Quantitative image assessment and complementary functional testing may therefore be required when CT results are insufficient for complete qualification.
For hydrogen refueling stations, metal hydride compressors offer a safe and efficient alternative to mechanical systems. This work systematically investigates Ti0.94Zr0.08Cr1.0Mn0.6−xFe0.4+x (x = 0, 0.1, 0.2, 0.3, 0.4) alloys for primary hydrogen compression targeting 25 MPa. All alloys crystallize as a single C14 Laves phase, with Fe substitution causing negligible lattice changes but leading to linearly increased particle size due to solid-solution strengthening. In the testing temperature range of −80 to −50 °C, the hydrogen storage capacity decreases with increasing Fe, whereas the effective desorption capacity improves. Pressure–composition isotherms exhibit single plateaus with elevated plateau pressures at higher Fe/Mn ratios. In the range of x = 0–0.4, the enthalpy of desorption decreases in magnitude with Fe content. Using Van’t Hoff extrapolations to 30 °C absorption and 80 °C desorption, the compression factor shows a non-monotonic trend, reaching a maximum of 1.99 at x = 0.2. This composition provides nearly a two-fold pressure boost, demonstrating promise for low-grade heat driven hydrogen compression in refueling infrastructure.
A quaternary electrolyte system consisting of sulfuric acid, boric acid, citric acid, and aluminum sulfate was developed to regulate oxide film growth and improve the corrosion resistance of hard anodic oxide films on 2A12 aluminum alloy. The electrolyte composition and anodizing parameters were systematically optimized using single-factor experiments and orthogonal design. The optimized oxide film exhibits a thickness of 55.43 μm and a microhardness of 278 HV, exhibiting a compact and continuous microstructure with fewer structural defects. SEM, EDS, XRD, and XPS analyses reveal that the optimized coating mainly consists of amorphous or poorly crystalline alumina. Electrochemical measurements demonstrate that the corrosion current density decreases from 5.32 × 10−5 A/cm2 for the substrate to 2.14 × 10−8 A/cm2, corresponding to a corrosion inhibition efficiency of 99.96%. The quaternary electrolyte system promoted the formation of a thicker and more compact oxide layer with fewer structural defects, thereby significantly enhancing the corrosion resistance and providing insights into the design of multicomponent electrolytes for the hard anodizing of high-copper aluminum alloys.
Additive manufacturing (AM) technologies, such as laser powder bed fusion (LPBF), allow for rapid fabrication of geometrically complex components that would be difficult to create using traditional casting or subtractive fabrication processes; however, research into AM metals has shown that fabrication defects resulting from LPBF processes (i.e., voids, un-melted particles, etc.) can have deleterious effects on mechanical behavior. Material testing using traditional macro (coupon-scale) volumes may not accurately capture scalable material behavior in LPBF metals, as the distribution of fabrication defects is volume-dependent. To understand fundamental material behavior at scales independent of geometrical fabrication defects (including print-induced material arrangements), in situ micro-mechanical testing of AM LPBF 17-4 PH stainless steel materials is conducted, opening possibilities for future bottom-up material simulation scaling. In this study, the tensile and compressive behavior of LPBF-fabricated 17-4PH stainless steel is characterized at the micron scale to aid future efforts in the predictive upscaling of structural components, while eliminating void effects and micro-scale print-induced material arrangements in any characterizations. Not surprisingly, behavior comparisons between multiple length scales (micro and macro scales) indicate strength reductions in larger bulk volumes. Micro-tensile measurements resulted in ultimate tensile strength (1359 MPa ± 99.9 MPa standard deviation) and strain before failure (0.31 ± 0.063 μm/μm) values that exceeded those of the macro-tensile specimens (1025 MPa tensile strength and 0.190 μm/μm strain at fracture, respectively).
This paper investigates the Electrode Induction Gas Atomization (EIGA) of a Class 4 tungsten heavy alloy (WHA-4) containing 97.8 wt.% W, with the balance comprising Ni and Fe. Compared with conventional tungsten heavy alloys containing less than 95 wt.% W, the high tungsten content reduces the liquid-phase fraction and melt fluidity, making stable processing significantly more challenging. Powder-metallurgy-fabricated electrodes were atomized under varying resonant induction conditions to evaluate the effects of capacitance, frequency, and input power on melt stability. The results show that stable processing can be achieved through an optimum combination of capacitance and resonant frequency, providing sufficient energy to maintain a steady melt stream and uninterrupted atomization. Under optimized conditions, predominantly spherical powders with minimal defects were successfully produced. Microstructural characterization revealed that the Ni–Fe binder phase remained localized along tungsten grain boundaries and in isolated pockets between tungsten grains. X-ray diffraction and chemical analyses confirmed that the phase constitution and alloy composition of the electrode were preserved during atomization. Under non-optimum conditions, process instability was associated with incomplete melting, beard formation, unstable melt flow, and nozzle blockage. These findings provide new insights into the atomization behavior of high-tungsten heavy alloys and establish practical processing procedures for producing high-quality WHA-4 powders for advanced manufacturing applications.
