Search Results (937)

Lightweight design is crucial for reducing inertial forces and vibrations in high-power-density reciprocating plunger pumps (RPPs). However, the tribological compatibility of lightweight alloys for crosshead–liner tribo-pairs is not well understood. This study systematically evaluates the friction and wear behaviors of six lightweight materials (TC4, TC4 (MAO), TC11, TC18, ZL108, and AlSi10Mg) sliding against HT250 gray cast iron under different lubrication conditions using an SRV IV tribometer. The results show that the lubrication regime significantly affects tribological performance. Water lubrication led to severe abrasive wear and high friction coefficients (0.75–0.91), while oil lubrication reduced friction to around 0.20 and promoted the formation of protective boundary films rich in P, S, and Zn. Material selection played a key role in wear mechanisms: aluminum alloys performed better under oil lubrication, whereas titanium alloys were more stable under water-lubricated conditions. MAO treatment on TC4 improved wear resistance, reducing the wear weight to less than 0.3 mg under oil lubrication by creating a strong ceramic oxide layer. Negative wear rates in lower specimens indicated material transfer from the upper specimen to the lower specimen. Based on performance metrics, the TC4-MAO/Shell 220 combination is recommended for lightweight crosshead applications. This study offers insights and guidelines for material selection to enhance the reliability and efficiency of future hydraulic equipment. Full article

The secondary dendrite arm spacing (SDAS) is a critical microstructural parameter that directly influences the local mechanical performance of Al–Si casting alloys. Although the power-law relationship between cooling rate and SDAS is widely acknowledged, the existing literature lacks a standardized framework for selecting the most appropriate solidification thermal interval for calculating this characteristic cooling rate. This study introduces an optimized methodological approach by evaluating solidification kinetics across two distinct thermal regimes: a standard non-isothermal sand mold (no chill) and an accelerated cast iron insert configuration (with chill). Cooling curves of a primary hypoeutectic AlSi7 Mg0.3 alloy were continuously recorded via ten calibrated K-type thermocouples along a wedge-shaped casting profile, and the corresponding local SDAS values were quantified using light optical metallography. By mathematically evaluating six distinct thermal analysis boundaries, the results demonstrate that conventional global intervals (e.g., liquidus-to-eutectic) yield lower predictive accuracy (R² ≈ 0.75) due to the accumulation of thermal “noise” from the early fluidic stage and the final eutectic reaction. In contrast, the localized interval bounded strictly between the Dendrite Coherency Point and the Rigidity Temperature (T_DCP − T_Rigidity) achieved excellent correlation for both the baseline slow-cooling regime (R² = 0.8509) and the accelerated regime (R² = 0.9547). This optimized window successfully isolates the exact kinetic timeframe of secondary dendritic evolution and effectively eliminates localized calculation anomalies across the entire spectrum of cooling rates. Thermodynamic analysis reveals a sharp cooling asymmetry in the wedge geometry, where the local solidification timescale collapses by a factor of 34 at the chill base. This extreme kinetic restriction limits the characteristic solute diffusion distance ($L\approx \sqrt{D.t}$) by a factor of nearly six (using representative solute diffusivities for Mg and Si in liquid aluminum), providing a quantitative physical basis for the significantly flatter coarsening slope (−14.85) under accelerated cooling compared to the baseline regime (−32.63). The proposed methodology establishes a physically grounded, highly accurate microstructural prediction tool suitable for advanced foundry engineering and casting simulations. Full article

Heat-treated A356 aluminum alloy has attracted sustained attention because of its low density, good castability and corrosion resistance. These properties make it valuable for automotive, structural and aerospace applications, while its final performance depends strongly on microstructural control. This review examines the microstructural evolution of A356 Al alloy from as-cast conditions through post-casting using various heat treatments. The emphasis is on the morphology and distribution of the primary α-Al matrix, eutectic Si phase and secondary intermetallic constituents such as Mg₂Si. It discusses how investment casting and other ingot metallurgy routes influence dendritic arm spacing, porosity formation and eutectic silicon morphology. This review answers the question “which heat treatment leads to better microstructural features and betterment of the mechanical properties?”. The review also highlights the role of T5 and T6 artificial aging, hot isostatic pressing and their combined effects on pore elimination, densification, hardness, ductility, tensile strength and fatigue resistance. In addition, the usefulness of EBSD for texture and grain structure analysis is considered as a route to deeper understanding of grain texture and orientation. Overall, the review shows that the performance of A356 alloy is governed by the interplay between casting-induced defects and heat-treatment-driven microstructural refinement; it also identifies processing routes that offer the best balance between strength, ductility and improved service life of components made from A356 Al alloy. Full article

Hot tearing limits the yield of Al–Zn–Mg billets produced by direct-chill casting. Its governing factors span composition, cooling conditions and the state of the partially solidified metal, and they interact; several quantities required by physics-based criteria cannot be measured during casting, and the factors are seldom observed together at plant scale. Machine learning was therefore used to establish, from variables that are recorded in production, which factors govern hot tearing when composition and process conditions vary simultaneously. Hot tearing was assessed in 108 pilot-scale billets covering several variants, and models were trained on alloy composition, casting parameters and calculated solidification characteristics. Evaluation used nested cross-validation with whole composition clusters held out, so that performance reflects unseen variants; the selected model attained a pooled out-of-fold average precision of 0.63 against a no-skill level of 0.51. Shapley additive explanations identified Si, Mn, Zn and steady-state casting speed as the dominant variables; the effect of Si depended on Fe content and that of Mg was non-monotonic. The contribution of Mn has not been documented systematically in this system. Attribution of the model yielded relations consistent with previously reported experimental findings, and these relations rest on variables obtainable in production, providing a basis for optimizing alloy design and casting processes. Full article

Post-quench natural aging can alter the response of Al–Mg–Si alloys to further artificial aging, while post-artificial-aging hardness, H_post-AA, may obscure changes in the retained artificial-aging response. Five high-purity alloys containing 0.95–0.99 mol% Mg + Si, with Mg/Si ratios of 0.52, 1.1, 1.9, 3.0, and 4.0, were solution-treated at 848 K for 3.6 ks, quenched, and artificially aged at 473 K. Under direct artificial aging, after a minimum practical delay of approximately 0.1 ks, the Mg/Si = 1.1 alloy showed the highest H_peak of approximately 72–73 HV0.1, whereas Mg/Si = 4.0 reached approximately 53–55 HV0.1. The precipitate areal density was highest near Mg/Si = 1 and decreased markedly in Mg-rich alloys. Operational HRTEM classification indicated that β″-related precipitates predominated in the Si-excess alloys, whereas β′-like and parallelogram-type precipitates were more prominent in the Mg-rich alloy. For Mg/Si ratios of 0.52, 1.9, and 4.0, quench-to-aging delays of up to 6000 ks produced non-monotonic changes in H_post-AA. However, the additional hardening increment, ΔH_AA, decreased from 38.5 to 26.1 HV0.1 at Mg/Si = 0.52 and from 33.5 to 26.9 HV0.1 at Mg/Si = 1.9. These results show that both H_post-AA and ΔH_AA are required to evaluate quench-to-aging delays. Full article

Hybrid lightweight structures increasingly combine cast, wrought, and additively manufactured aluminum alloys, but the mechanical response of their welded joints remains strongly material-dependent. In this study, cast EN AC-42100-T6, wrought EN AW-6082-T6, and laser powder bed fusion (LPBF) AlSi10Mg stress-relieved plates were welded in 4 and 8 mm configurations using cold metal transfer and pulsed multi-control processes over two campaigns. Weld defects, microstructure, hardness profiles, and tensile properties were analyzed using a framework combining a hardness derived local yield-stress descriptor (σ_y,loc), a cumulative hardness deficit (ID_HV), and a porosity increment metric (ΔP). The second campaign eliminated fusion and penetration related defects, but did not mitigate fusion zone porosity in LPBF-related joints, which reached 13.7% in the 8 mm LPBF–Cast joint. Hardness analysis showed the widest hardness-affected region in the wrought alloy, an intermediate response in the cast alloy, and localized alteration in LPBF. Tensile results identified three degradation modes: strength loss associated with heat-affected zone (HAZ) softening in wrought-containing joints, ductility limitation associated with the initial cast condition, and porosity-associated ductility loss in LPBF-related joints. The lower yield strength reduction in LPBF-related joints does not imply improved performance, as fracture remains strongly influenced by fusion zone porosity. The results support material specific mitigation and design strategies for hybrid welded aluminum structures. Full article

High-fidelity finite-element (FE) simulation of nonlinear full-field responses in AlSi10Mg tensile specimens is computationally expensive, while the available digital image correlation (DIC) data in this study consist only of engineering-strain screenshots rather than exportable numerical fields. This work therefore develops a simulation-to-experiment framework for rapid full-field stress prediction and weakly supervised DIC-informed spatial regularization. Two hundred independent Abaqus/Explicit loading cases generated 5600 graph samples, which were used to train an eight-layer FiLM-conditioned graph neural network for nodal von Mises stress and three-component displacement prediction, together with a decoupled structured force–displacement branch. On independent FE tests, von Mises stress prediction achieved R² = 0.9984 with an RMSE of 4.60 MPa, while the dense force–displacement curve achieved R² = 0.9957 and RMSE = 59.70 N. Five machine tensile tests gave mean pre-fracture curve NRMSEs of 4.40% for FE versus experiment and 5.31% for GNN versus experiment. On independent specimens L-7 and L-8, the constrained adapter reduced DIC spatial shape loss by 3.21% with a mean absolute stress correction of 0.232 MPa. The framework therefore provides rapid FE-surrogate prediction with conservative experiment-informed spatial regularization rather than experimental stress inversion. Full article

Recycled aluminum has emerged as an excellent alternative for producing new alloys. The development of multicomponent alloys has led to products with enhanced properties, and the aluminum alloy market has increased. This study utilized squeeze casting to produce Al alloy samples. The effects of 5 wt.% of both the Si content and the Al-25.5 Cu−12 Fe quasicrystal (QC) content on the microstructural formation and microhardness analyzed. A cellular microstructural formation was found for the recycled aluminum. A dendritic structure was characterized in both the Alrec−5% Si and Alrec−5% QC alloys. After adding 5% wt.% QCs, the resulting hardness became higher (varying between 110 and 130 HV) than the alloy with 5 wt.% Si (90 and 110 HV) and the recycled aluminum alloy (between 70 and 80 HV). The portion of the QC alloy completely dissolved into the bulk of the recycled alloy during squeeze casting. This was associated with a more complex phase arrangement characterized by the QC alloy. This was characterized by a dendritic microstructural array with binary eutectic mixtures (α-Al + Mg₂Si) and refined ternary eutectic mixtures (α-Al + Mg₂Si + AlFe(Si)). In contrast, the sample with Si content and the recycled alloy sample without additions depicted resulting microstructural arrays with reduced secondary phase formations. These contributed to improved mechanical behavior through traditional strengthening mechanisms. Full article

Graphene nanoplatelets (GNPs)-reinforced AlSi10Mg composites were fabricated by selective laser melting (SLM), and their corrosion resistance was systematically investigated as a function of GNPs content (0, 0.1, 0.3, and 0.5 wt.%) and corrosion duration. In the short term (≤30 days), the corrosion resistance followed the order: 0.1 wt.% GNPs/AlSi10Mg > 0.3 wt.% GNPs/AlSi10Mg > 0.5 wt.% GNPs/AlSi10Mg > AlSi10Mg. The 0.1 wt.% composite exhibited the best performance, attributed to the uniform dispersion of GNPs that filled micropores and microcracks to form a physical barrier against corrosive ions, along with favorable interfacial bonding that hindered crack growth and reduced corrosion pathways. After 60 days of exposure, however, the ranking reversed to: AlSi10Mg > 0.1 wt.% GNPs/AlSi10Mg > 0.3 wt.% GNPs/AlSi10Mg > 0.5 wt.% GNPs/AlSi10Mg. EIS analysis revealed a porous electrode behavior in the low-frequency response, captured by the constant phase element in the equivalent circuit. The long-term deterioration arose from the gradual penetration of corrosive media through micropores and microcracks, which triggered galvanic corrosion between GNPs and the matrix and rendered the barrier effect ineffective. These findings demonstrate that GNPs addition increases both the number and the total area of cathodic sites in the matrix alloy, thereby accelerating corrosion under prolonged exposure. In essence, GNPs serve as a protective barrier in the short term but transition to corrosion accelerators under long-term exposure. Full article

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. Full article

Nickel coatings were deposited onto the surfaces of red mud, Al₂O₃, and Fe₂O₃ particles via an electroless plating technique. The nickel-coated particles (1.5 wt.%) were subsequently incorporated into a ZL109 aluminum alloy matrix to fabricate three types of composites using a stir-casting process, followed by a T6 heat treatment consisting of solution treatment at 515 °C for 8 h, water-bath quenching at 90–100 °C, and artificial aging at 175 °C for 12 h. The microstructural morphology and phase identification were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Furthermore, the high-temperature tensile properties of the fabricated alloys were evaluated at 350 °C and 400 °C. The results showed that the addition of 1.5 wt.% nickel-coated red mud led to a more uniform distribution of eutectic silicon and an increase in the content of the Al₅Cu₂Mg₈Si₆, Al₇Cu₄Ni, and Al₂Cu strengthening phases. These microstructural changes significantly enhanced the high-temperature tensile performance of the alloy. At 350 °C and 400 °C, the alloy reinforced with 1.5 wt.% nickel-coated red mud achieved tensile strengths of 97.8 MPa and 86.2 MPa, respectively. The combination of an appropriate amount of nickel-coated red mud and a suitable heat treatment process effectively improves the high-temperature stability and tensile properties of the ZL109 aluminum alloy, which could be attributed to the synergistic strengthening effect arising from the precipitation of high-temperature stable phases and the Orowan mechanism. Full article

Grain boundaries affect the mechanical and functional properties of crystalline materials by influencing interfacial energy, mobility, segregation, and the accumulation of damage. Among the grain boundaries in the grain boundary network, coincidence site lattice boundaries form a particular type of special grain boundary that is characterized by a higher degree of lattice-site coincidence. The present study examined the mechanisms involved in the formation of grain boundaries in a laser-powder-bed-fused AlSi10Mg alloy which had been subjected to two-pass twist equal-channel angular pressing (twist-ECAP). The microstructural evolution, deformation texture, and local orientation gradients were investigated using electron backscatter diffraction (EBSD). Moreover, atomistic simulations were carried out in order to assess the effect of geometrically necessary boundary (GNB)-like dislocation walls on the retention of planar faults. The EBSD results indicated that twist-ECAP considerably refined the microstructure and produced a strong fiber texture. Most of the Σ3 grain boundary segments detected were found in areas dominated by the ⟨110⟩||ED component, showing that their appearance is strongly dependent on the texture. Also, the atomistic modelling showed that the presence of a GNB-like wall led to the retention of planar-fault configurations and thus resulted in the highest number of atomic environments related to faults and extended dislocation-line lengths. These results show that the formation of Σ3 grain boundary segments in severely deformed LPBF AlSi10Mg is a coupled process which is mainly controlled by macroscopic texture selection and is locally assisted by deformation-boundary evolution. Full article

Deployable metallic structures offer a new design approach for overcoming the geometric limitations of laser powder bed fusion by enabling compact as-built configurations to be expanded after printing into larger, lightweight architectures suitable for efficient packing and aerospace applications. The formability of solution heat-treated, additively manufactured AlSi10Mg alloy was investigated using U-shaped specimens with controlled radius and thickness parameters, designed to evaluate bending-driven deployment. Across all configurations, the alloy exhibited substantial plastic deformation, reaching bending angles between 90.2° and 179.5°. Full deployment was achieved in the t2 r4 specimen, corresponding to an r/t ratio of 2.0, which straightened to 179.5° without failure while maintaining the lowest measured strain of 18.8%. Experimental observations and numerical analysis indicate that failure is governed not by a single critical strain, but by strain localization at the inner radius, followed by surface slip, crack initiation and crack propagation. These findings demonstrate that heat-treated AlSi10Mg provides a promising route towards lightweight, additively manufactured deployable structures with tunable deformation capacity. Full article

Additively manufactured AlSi10Mg aluminum alloy was investigated at two-layer build orientations: 0° and 90°. Impact-induced fractures were generated per the ASTM standard Charpy test. The resulting fracture surfaces were analyzed using the multi-image-based fractal analysis method. We used a digital microscope to analyze the fracture surface and examined compression, neutral, and tension zones on the surface. We found that the crack propagated symmetrically across the surface. The results showed that the compression zone has the lowest fractal dimension compared to the tension and neutral zones. The 0° orientation samples have a higher fractal dimension than the 90° orientation samples. Full article

This paper investigates the stress corrosion cracking (SCC) behavior under constant loading conditions and the early-stage grain-scale deformation mechanisms of a friction-stir-welded (FSW) joint of 7A52 aluminum alloy. The results show that when a constant load equivalent to 1.0 times the yield strength (439.43 MPa) of the base metal is applied, the joint fractures after 72 days of immersion in a 3.5 wt% NaCl solution, with the fracture located in the heat-affected zone on the advancing side (AS-HAZ). The fracture surface exhibits a mixed-mode morphology characterized by both brittle and ductile features. Observations suggest that cracks mainly initiate at the bottom of corrosion pits, at grain boundaries, and at the interfaces between precipitates (such as Mg-Si-rich, Al-Fe-rich, or Al-(FeMn)-rich) and the Al matrix. It is suggested that the initiation mechanisms are closely related to galvanic corrosion, interfacial weakening, and mechanical property mismatch. In situ tensile and EBSD results indicate that the AS-HAZ is the first region to undergo deformation. As the load increases from 400 N to 1500 N, the degree of strain localization intensifies, with high-strain regions preferentially concentrated at grain boundaries. Grain boundary damage is likely a key mechanism responsible for the initial failure on the advancing side of the FSW joint. Further in situ SEM observations reveal that during the early stage of tensile deformation, as the load increases from 300 N to 455 N, the grain surface in the AS-HAZ evolves from a flat morphology to a typical orange peel appearance. Meanwhile, grain boundaries change from clearly visible to blurred, slip traces increase, and multiple slip systems are activated within the grains. The continuous pile-up of dislocations at grain boundaries leads to a sharp increase in local stress concentration, ultimately inducing grain boundary instability and crack nucleation. Full article