Search Results (139)

This study focuses on how modulating the electrical pulse frequency alters both the topographic features and corrosion resistance of ceramic coatings produced via micro-arc oxidation (MAO) on an AZ31B magnesium substrate. In a silicate-based electrolyte, MAO treatments were executed utilizing four distinct frequencies: 300, 500, 800, and 1000 Hz. Phase configurations, microstructural features, and surface patterns were thoroughly evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM) integrated with energy dispersive spectroscopy (EDS), and an ultra-depth-of-field microscope. Furthermore, the fabricated coatings underwent rigorous assessments for their porosity, contact angle, Vickers hardness, and electrochemical attributes. The outcomes demonstrate that the surface appearance, phase structure, defect state, and density of the MAO coatings are highly sensitive to variations in pulse frequency. Notably, although the coating prepared at 800 Hz exhibited elevated surface roughness (Ra), it achieved a highly consolidated microstructure and the lowest porosity level, underscoring that roughness alone is not a definitive quality indicator. This structural refinement was driven by the presence of well-crystallized Mg₂SiO₄ and MgO phases. This group recorded a peak inner barrier layer resistance (R_b) of 1.62 × 10⁴ Ω·cm² alongside a minimum corrosion current density (I_corr) of 3.38 × 10⁻⁷ A·cm⁻², confirming its exceptional protective capacity. Consequently, the structural quality and corrosion resistance of MAO coatings can be strategically enhanced by tuning the electrical frequency, offering valuable engineering guidelines for utilizing AZ31B alloy parts under aggressive environmental conditions. Full article

In order to verify the reliability and engineering applicability of the AE-CMT welding technology for magnesium alloy joining, AE-CMT welding experiments were conducted at welding speeds ranging from 0.5 to 3.0 m/min on 1.5 mm-thick H24-temper AZ31B magnesium alloy sheets using imported 1.2 mm-diameter WE-33M welding wire. Within the welding speed range of 0.5–3.0 m/min, increasing the welding speed progressively reduces heat input, thereby refining grains and homogenizing the microstructure. The welding heat input of the AE-CMT process ranges from 0.47 KJ/mm to 1.07 KJ/mm, and the grain sizes of the weld zone and HAZ are 9.61–14.18 μm and 6.35–12.22 μm, respectively. In the range of 0.5–2.0 m/min welding speed, increasing welding speed progressively enhances the tensile strength of the welded joint. Notably, joints fabricated at a welding speed of 2.0 m/min deliver the maximum tensile strength, equivalent to 98.0% of the base metal. Well-defined dimples are also detected on the corresponding fracture surfaces. A further increase in welding speed leads to a gradual reduction in the tensile strength of the welded joint. It is demonstrated that welding speed acts as a critical process parameter for tailoring the microstructure and mechanical properties of AE-CMT-welded AZ31B magnesium alloy joints. Full article

High-velocity oxy-fuel (HVOF)-sprayed NiCrBSi coatings containing 0, 10, 30, and 50 wt.% WC-Co were evaluated on AZ91D magnesium alloy to determine how the discrete reinforcement level affects surface topography, phase constitution, Vickers microhardness, dry-sliding friction, mass loss, and wear-track microchemistry. As-sprayed surfaces were characterized by three-dimensional profilometry; coating cross-sections and worn surfaces by optical microscopy and SEM/EDS; phase constitution by XRD; and mechanical response by HV_0.1 indentation. Dry-sliding tests were performed at 10, 30, and 50 N over 100–1000 m. Increasing WC-Co content raised Sa from 8.8 ± 0.3 to 13.0 ± 0.5 µm and Vickers microhardness from 776 ± 4 to 959 ± 5 HV_0.1. XRD indicated a γ-Ni-based matrix containing boride/carbide constituents, while WC, W₂C, and Co became increasingly prominent in the reinforced coatings. Boride assignments are based on diffraction evidence, whereas B and C EDS signals were treated semi-quantitatively. The 50 wt.% WC-Co coating exhibited the lowest mass loss and mean coefficient of friction at every load. Its mean friction coefficients were 0.31, 0.35, and 0.41 at 10, 30, and 50 N, corresponding to reductions of 40.1%, 38.9%, and 36.2% relative to AZ91D. At 1000 m, its mass-normalized wear rate indices were 9.0 × 10⁻⁴, 4.0 × 10⁻⁴, and 5.3 × 10⁻⁴ mg N⁻¹ m⁻¹, respectively. Post-wear mapping showed the largest field-scale W-Co-rich fraction in the 50 wt.% coating; however, isolated spectra containing more than 94 wt.% Mg are compatible with local coating penetration/substrate exposure and/or Mg-rich debris. The 50 wt.% composition therefore provided the best combined response among the four tested levels, while intermediate compositions are required to identify a continuous-composition optimum. Full article

The use of five machine-learning regression models, Gaussian Process Regression (GPR), Support Vector Machine (SVM), XGBoost, CatBoost, and LightGBM, was for predicting the ultimate tensile strength (UTS) of friction stir welded (FSW) AZ31B magnesium alloy joints. A controlled, single-source, experimental dataset comprising 99 observations was created on the same FSW machine under the same laboratory conditions. The dataset covered three feed rates, eleven rotational speeds and three tool tilt angles, and each parameter combination was represented by the mean UTS value from triplicate tensile tests. The input variables were the feed rate, rotational speed and tilt angle, and the prediction target was UTS measured using ASTM E8M-04. To create a more challenging and realistic assessment, we implemented blocked-holdout validation, keeping only the previously unseen rotational speed levels for the test set. Hyperparameters were selected via exhaustive grid search, with 5-fold GroupKFold cross-validation used solely on the training data. Among the models that were tested, GPR demonstrated the best overall blocked-holdout performance, with a R² = 0.985 and RMSE = 1.798 MPa. XGBoost (R² = 0.923) and CatBoost (R² = 0.912) also demonstrated competitive performance. Conversely, LightGBM exhibited the poorest generalization performance (R² = 0.817). The findings suggest that kernel and boosting-based approaches have the capacity to adequately simulate the nonlinear relationship between FSW process parameters and tensile performance, while GPR demonstrated the best generalization under the blocked-holdout evaluation strategy. Full article

Driven by the automotive industry’s strategies for energy conservation, emission reduction, and lightweighting, magnesium alloy wheels have emerged as a key focus of research and industrialization efforts, owing to their high specific strength, excellent vibration-damping properties, and superior heat dissipation performance. This paper provides a systematic review of the performance advantages, material systems, forming processes, applications, and industrialization challenges of magnesium alloy automotive wheels. The core advantages of magnesium alloy wheels in terms of weight reduction, vibration damping, and thermal management are elaborated. The compositional characteristics, suitable processes, and performance differences between cast magnesium alloys (e.g., AZ91D, AM60B) and wrought magnesium alloys (e.g., AZ80, ZK61-Y) are outlined. The technical characteristics, microstructural and property evolution, and limitations of casting processes (gravity, high-pressure, low-pressure, and semi-solid casting), plastic forming processes (isothermal extrusion forging, backward extrusion forging, and spin forming), and hybrid processes are discussed. Combined with the case studies of magnesium alloy wheel applications in the automotive sector, this paper analyzes the core bottlenecks of magnesium alloy wheels in terms of corrosion resistance, production cost, and industrial consistency, and outlines future research directions. This paper aims to provide theoretical references and technical support for the design, manufacturing, and large-scale application of lightweight, high-performance magnesium alloy wheels. Full article

This paper investigates the influence of surface ultrasonic rolling treatment on the fatigue performance of Mg-3Al-1Zn extruded alloy and systematically analyzes the evolution laws of fatigue life and mechanical properties with the thickness of the surface removed layer. The results show that after ultrasonic rolling treatment, the fatigue life of the alloy at a stress amplitude of 240 MPa changes significantly and reaches a peak at a specific removal thickness: when the 80 μm surface layer is removed, the fatigue life reaches 7.79 × 10⁶ cycles, which is much higher than that of the untreated sample (3.87 × 10⁴) and the sample only subjected to ultrasonic surface rolling processing (1.8 × 10⁴). With the increase in the removal thickness, the fatigue life shows a trend of first increasing and then decreasing, and a second increase occurs within the range of 400–500 μm. Microstructure analysis indicates that at a depth of 80 μm from the surface, the strength is enhanced due to grain refinement and the peak hardness, thereby inhibiting the initiation of fatigue cracks, while within the depth range of 400–500 μm, there exist high-density dislocations and deformation layers, which also effectively hinder crack propagation. This study reveals the key role of surface state and subsurface microstructure in the fatigue behavior of magnesium alloys, providing a theoretical basis for improving the fatigue performance of magnesium alloys through surface modification. Full article

The rapid advancement and widespread application of telecommunication technologies have significantly increased human exposure to electromagnetic waves, thereby intensifying the demand for effective electromagnetic shielding materials. Beyond potential health concerns, ensuring the stable performance of highly integrated electronic devices also necessitates protection against electromagnetic interference (EMI). In this study, the effects of processing conditions on the EMI shielding effectiveness (SE) of AZ61 magnesium alloy sheets were systematically investigated. Aging treatment of rolled AZ61 alloy promoted the formation of Mg₁₇Al₁₂ lamellae. Transmission Kikuchi diffraction analysis revealed that plate-like Mg₁₇Al₁₂ precipitates preferentially formed on the (0001) planes of the Mg matrix, contributing to improved EMI shielding. The rolled AZ61 sheet exhibited the highest SE in both the as-rolled state (83.1 dB at 900 MHz) and after aging for 131 h at 250 °C (76.2 dB at 900 MHz). The superior shielding performance of the as-rolled sheet is attributed to its high density of deformation-induced defects such as dislocations and twins, which induce lattice distortions and impede wave propagation. Meanwhile, the enhanced SE from the 131 h-aged condition results from multiple reflections of incident electromagnetic waves facilitated by the matrix–precipitate lamellar microstructure. Full article

Organic coatings are used as one of the most effective strategies for the corrosion protection of metals. Nowadays, due to environmental regulations, the use of water-based coatings has become essential compared to solvent-based ones. However, their application to magnesium alloys remains largely unexplored due to their high reactivity with water. In the present work, a phosphate-functionalized waterborne binder is applied to AZ31B magnesium alloy. The surface has been modified by four different pre-treatments, respectively: (i) mechanical grinding, (ii) pickling, (iii) conventional conversion treatment, and (iv) a novel conversion treatment based on layered double hydroxides (LDH). The most promising pre-treatments are selected to explore their synergy with a biobased waterborne binder, containing CeO₂ nanoparticles as a corrosion inhibitor. The morphology and composition of the different systems are studied, prior to and after corrosion tests in NaCl solution, by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Results obtained by electrochemical impedance spectroscopy (EIS) in NaCl solution have revealed not only that LDH performs better than the conventional conversion treatment but also the synergy between LDH pre-treatment and CeO₂ nanoparticles when two organic layers are used. Full article

To mitigate the intrinsic high corrosion susceptibility of AZ31B magnesium alloy, a three-step synergistic surface modification strategy was developed in this work: initially, a MgO ceramic coating was in situ fabricated on the AZ31B substrate via micro-arc oxidation (MAO); subsequently, a TiO₂ sealing barrier layer was deposited on the MAO coating through a deep ultraviolet (DUV)-assisted sol–gel method; finally, a superhydrophobic top layer was constructed via fluoroalkylsilane (FAS) self-assembly. The microstructural characteristics, chemical compositions and corrosion resistance of the coatings at different modification stages were comprehensively characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), water contact angle (WCA) measurements and electrochemical tests. The results showed that the as-deposited TiO₂ was predominantly anatase phase, and FAS molecules were firmly anchored on the coating surface via Si-O-Ti covalent bonds, endowing the composite coating with a WCA of up to 160°. Electrochemical tests demonstrated that the FAS-TiO₂-MAO composite coating exhibited an ultra-low corrosion current density of 1.31 × 10⁻⁹ A/cm² and a remarkably high charge transfer resistance (R_ct) of 3.46 × 10⁸ Ω·cm². Compared with the bare AZ31B substrate, the corrosion current density was decreased by nearly four orders of magnitude, while the charge transfer resistance was enhanced by approximately six orders of magnitude, indicating a significant improvement in corrosion resistance. Moreover, the composite coating exhibited excellent interfacial adhesion, favorable mechanical durability, and outstanding chemical stability, confirming its reliable long-term corrosion protection and high practical application potential. This work provides a feasible strategy for fabricating high-performance superhydrophobic anticorrosive coatings on magnesium alloys. Full article

Edge cracking is prone to occur during the rolling of Mg/Al composite foils. Herein, a hybrid hot–cold rolling process was adopted to fabricate 30 μm thick Mg/Al composite foils with low edge cracking. AZ31B magnesium alloy and 5052 aluminum alloy sheets, both with an initial thickness of 0.5 mm, were chosen as research materials. Numerical simulations of composite pass were conducted at 300–450 °C with reduction ratios of 25–40%, and the optimal parameters were identified as 400 °C and a 35% reduction ratio. Based on this, multi-pass rolling experiments were performed: composite pass was heated at 400 °C for 10 min with 35% reduction ratio, hot rolling passes at 300 °C for 1–3 min, and subsequent cold rolling with 15% reduction ratio. After 21 rolling passes, 30 μm thick Mg/Al composite foils with low edge cracking were successfully prepared. Interface and metallographic characterizations demonstrated that the diffusion layer thickness varied slightly during hot rolling and increased moderately during cold rolling. For the magnesium alloy, hot rolling improved microstructural uniformity and reduced shear bands, while cold rolling caused decreased uniformity and the gradual emergence of shear bands. The research results provide a reference for the preparation of high-quality Mg/Al composite foils. Full article

Friction stir welding (FSW) was employed to achieve a reliable joining of 2 mm thick dissimilar metals, 6061 aluminum alloy and AZ31B magnesium alloy. This study revealed the evolution of interfacial interlocking features and their impact on the mechanical properties of the joints under different welding speeds (25–35 mm/min). The results indicate that the Al/Mg FSW joint interface exhibits a strip-like interlaced structure, the morphological characteristics of which are closely related to the welding speed. For quantitative analysis, the ratio of interlocking length to plate thickness (embedding ratio) was used as a quantitative indicator of the structural interlocking feature. As the welding speed increased from 25 mm/min to 35 mm/min, the embedding ratio decreased from 13.2 to 7.9, and the average thickness of the intermetallic compound (IMC) layer decreased from 2.71 μm to 2.19 μm. Transmission Electron Microscopy (TEM) results confirmed that the Al/Mg FSW joint interface consists of a bilayer of IMCs, specifically Al₃Mg₂ and Al₁₂Mg₁₇, with thicknesses of 220 nm and 470 nm, respectively. Tensile testing of joints with different embedding ratios demonstrated that the tensile strength of the welded joint exhibits a positive correlation with the embedding ratio, reaching a maximum of 178 MPa. Full article

Magnesium alloys, like AZ31, possess a desirable low weight and high specific strength, which make them favorable for aerospace and auto applications, yet their difficulty to machine limits their broader implementation for the industry. Electrical discharge machining (EDM) is an effective technology for machining difficult-to-machine materials, particularly when the materials are reinforced with ceramic and graphene-based fillers. This study examines the impact of reinforcement percentage (R) and different electrical discharge machining (EDM) parameters such as current (I), pulse on time (T_on) and pulse off time (T_off) on the material removal rate (MRR) and surface roughness (SR) of AZ31/B₄C/GNPs composites. The combined reinforcement range varies from 2 wt.% to 4 wt.%. The Taguchi design (L27) is utilized to conduct the experiments in this study. ANOVA of the experimental data indicated that current (I) significantly affects MRR and SR, exhibiting the greatest contribution of 44.93% and 51.39% on MRR and SR, respectively, among the variables analyzed. The surface integrity properties of EDMed surfaces are examined using SEM under both higher and lower material removal rate settings. Diverse machine learning techniques, including linear regression (LR), polynomial regression (PR), Random Forest (RF), and Gradient Boost Regression (GBR), are employed to construct an efficient predictive model for outcome estimation. The built models are trained and evaluated using 80% and 20% of the total data points, respectively. Statistical measures (MSE, RMSE, and R²) are utilized to evaluate the performance of the models. Among all the developed models, GBR exhibited superior performance in predicting MRR and SR, achieving high accuracy (exceeding 92%) and lower error rates compared to the other models evaluated in this work. This work demonstrated the synergy between techniques in optimizing EDM performance for hybrid composites using a statistical design and machine learning strategies that will facilitate greater use of hybrid composites in high-precision engineering applications and advanced manufacturing sectors. Full article

To explore the influence of the microstructure of plasma electrolytic oxidation (PEO) coating on the loading of corrosion inhibitors and the silanization treatment on its surface, PEO coatings were first prepared on the surface of AZ31B magnesium alloy under different voltages. Secondly, sodium tungstate (Na₂WO₄) was loaded into the micropores and onto the surface of the PEO coatings via vacuum impregnation, and which were subsequently subjected to silanization treatment. The phase composition of the coatings was studied by XRD, while the elemental composition and valence state were investigated by XPS. The surface and cross-sectional morphology of the coatings, as well as the composition and distribution of elements, were studied by SEM and EDS. Image J software was employed to analyze the thickness of the coatings. The results show that the microstructure of PEO coatings prepared under different voltages varies, which affects the loading of Na₂WO₄ on the surface of PEO coating and the sealing effect of silanization treatment, thereby influencing the corrosion resistance of the coatings. As the voltage increases, the coating thickness and roughness gradually increase, while the surface porosity first increases and then decreases, and the loaded content of Na₂WO₄ also follows a trend of first increasing and then decreasing. Meanwhile, at 300 V and 350 V, silanization treatment effectively seals the PEO coatings loaded with Na₂WO₄. However, when the voltage increases to 400 V, due to the uneven surface of the PEO coating, nonuniform distribution of micropores, and high roughness, the silanization treatment fails to completely cover the coating. This results in defects such as pits on the surface of the composite coating prepared at 400 V. Therefore, the composite coating prepared at 350 V exhibits the best corrosion resistance. After immersion in a 3.5 wt.% NaCl solution for 240 h, the composite coating formed at 350 V remains intact, and its low-frequency impedance modulus |Z|_0.01Hz is as high as 1.06 × 10⁶ cm². This value is approximately two orders of magnitude higher than that of the composite coating fabricated at 400 V and about three orders of magnitude higher than that of the pure PEO coating prepared at 350 V. Full article

Magnesium as a biodegradable metal implant has garnered attention. Nevertheless, its rapid degradation rate and insufficient osseointegration restrict its clinical applications. In order to enhance the corrosion resistance and bioactivity of magnesium alloys, superhydrophobic hydroxyapatite (HA) layers were synthesized on micro-arc oxidized (MAO)-treated AZ31B magnesium alloy through liquid-phase deposition. This study examined the surface morphology, phase composition, bonding strength, wettability, electrochemical properties, and in vitro mineralization of the synthesized coatings. The study results demonstrated that the improved corrosion resistance of composite coatings in Hank’s solution is due to the formation of a protective HA layer. The inclusion of the MAO coating significantly enhances the bonding strength between the hydroxyapatite (HA) layer and the bare magnesium alloy. The concentration of NaH₂PO₄ affects both the microstructure and wettability. The composite coating exhibited excellent osseointegration capabilities, with new HA layers observed after immersing the samples in simulated body fluid (SBF) solution for three days. These findings suggest that the combination of MAO and solution treatment presents a promising method for enhancing biocompatibility and reducing magnesium degradation, thus making it a viable option for biodegradable implant applications. Full article

This study presents a systematic investigation into the influence of pulse frequency on the micro-arc oxidation (MAO) coating of AZ31B magnesium alloy following electron-beam remelting (EBR). The morphology, thickness, and corrosion resistance of the EBR-MAO composite coating were meticulously analyzed across various pulse frequencies (100 Hz, 200 Hz, 300 Hz, 400 Hz) employing scanning electron microscopy (SEM), X-ray diffraction (XRD), and electrochemical measurement techniques. The results show that as the pulse frequency escalates from 100 Hz to 400 Hz, the average thickness of the EBR-MAO composite coating diminishes from 41.1 μm to 38.5 μm, reduced by 6.7% compared to 10.4% in the MAO coating. Concurrently, the porosity exhibits a reduction from 1.93% to 1.35%, accompanied by a densification of the coating’s structure. High pulse frequencies yield coatings with enhanced smoothness and fewer defects. Notably, the corrosion resistance of the coatings demonstrates significant improvement at higher frequencies (400 Hz) compared to their lower-frequency (100 Hz) counterparts, as evidenced by a tenfold increase in corrosion current density. This research underscores the pivotal role of pulse frequency in optimizing the protective qualities of MAO coatings on magnesium alloys. Full article