Search Results (468)

To address the demand for lightweight, high-performance Al-Si-Mg alloys in aerospace and automotive industries, this work proposes a novel synergistic strengthening strategy by combining rare-earth Y microalloying and in situ synthesized ZrB₂ nanoparticles to construct a hybrid reinforcement architecture. The effects of Y-ZrB₂ additions on the microstructure, crystallographic orientation evolution, and mechanical properties of Al-Si-Mg alloys were systematically investigated via XRD, SEM, EBSD, and tensile/hardness tests. Results show that compared with the base alloy and single-modified alloys, the co-addition of Y and ZrB₂ simultaneously enhances mechanical properties and optimizes grain structure. The optimal comprehensive performance is achieved at 0.3 wt.% Y + 2 wt.% ZrB₂ after T6 heat treatment, with ultimate tensile strength of 332.87 MPa, yield strength of 271.35 MPa, elongation of 16.24%, and Vickers hardness of 153.9 HV. Phase analysis and SEM-EDS confirm a synergistic coupling relationship between Y-rich phases and ZrB₂ nanoparticles. EBSD characterization reveals that Y-ZrB₂ modification has negligible effect on the morphology and crystallographic orientation stability of primary α-Al grains, but effectively regulates the lattice rotation, texture redistribution, and growth behavior of eutectic Si. At the optimal composition, the fraction of high-angle grain boundaries (HAGBs) reaches a maximum of 34.3%. Furthermore, the synergistic effect significantly increases the geometrically necessary dislocation (GND) density and reduces the Schmid factor of the dominant {111}⟨110⟩ slip system, thus enhancing dislocation strengthening and plastic deformation resistance. This work clarifies the intrinsic strength-ductility synergy mechanism of Y-ZrB₂ co-modified Al-Si-Mg alloys, paving a new pathway for the development of advanced lightweight aluminum alloys. Full article

Scandium (Sc) is well recognized as a potent grain refiner, yet optimizing its addition amount in the Al-Cu-Mg-Ni-Fe (A242) system remains a longstanding challenge, critically important for material performance in high-temperature automotive and aerospace applications. The present work, therefore, presents a study of low-Sc modified A242 alloys, demonstrating that 0.2 wt.% Sc microalloying of the system has a pronounced effect on its solidification-driven microstructural evolution, improving the high-temperature formability of the alloy over a 20–200 °C temperature range. The study demonstrates that this addition triggers a dramatic columnar-to-equiaxed grain transition, reducing the average grain size by 90.8% (from 400 ± 100 μm to 37 ± 10 μm) and fragmenting the brittle, continuous intermetallic network into a highly uniform architecture. Uniaxial compression testing revealed that, while the as-cast solid-solution alloy slightly reduces room-temperature strength due to solute trapping, it delivers an exceptional 142% increase in strain-to-failure at 200 °C (exceeding 0.8 mm) compared to the base alloy. This significant enhancement in ductility is driven by thermally stable Al₃Sc dispersoids that exert Zener pinning pressure, halting thermal grain coarsening and activating superplastic deformation mechanisms. These findings support the development of advanced thermoforming applications, with the finite element (FE) model predicting process improvements that enhance manufacturing efficiency. This work presents a validation and simulation-ready material framework that substantiates the viability of low-Sc-modified A242 alloys for such operations. Full article

Wind turbine towers rely on welded joints for structural continuity, and the coarse-grained heat-affected zone (CGHAZ) at these joints is the principal site of fatigue damage under service loading. This study characterises the influence of welding heat input on the microstructural constitution, high-cycle fatigue response, and fracture mechanisms of Gleeble-simulated CGHAZs in a Nb-microalloyed wind power steel. Thermal cycles representative of submerged arc welding at 15, 25, 35, and 45 kJ/cm were applied, and the resulting microstructures were examined by optical microscopy, SEM, EBSD, and TEM. Raising the heat input produced systematic microstructural coarsening: the densities of low-angle grain boundaries (LAGBs) and high-angle grain boundaries (HAGBs) fell by approximately 40% and 26%, respectively, while the mean equivalent diameter (MED) and prior austenite grain (PAG) size grew by roughly 64% and 67%. Life partitioning showed that crack nucleation accounted for more than 84% of total fatigue cycles in every condition, identifying it as the life-governing damage stage. Over the 15-to-45 kJ/cm range, the CGHAZ fatigue strength at 2 × 10⁶ cycles deteriorated from 246.9 MPa to 208.5 MPa (a 15.6% reduction), while the mean fatigue striation spacing widened from 0.142 μm to 0.183 μm (an increase of 28.9%). These results demonstrate that judicious heat-input selection is a practical and effective means of preserving CGHAZ fatigue integrity in wind tower steel fabrication, and they address a previously unresolved gap concerning high-cycle fatigue fracture mechanisms in this critical microstructural zone. Full article

The corrosion behavior of copper and a Cu-Fe-P alloy in 3.5% NaCl solution was studied in this paper. This study focused on the influence of microalloying in the Cu-Fe-P alloy containing 0.003 wt% Fe and 0.014 wt% P on corrosion resistance in chloride media. Additionally, the effect of 2-mercapto-1-methylimidazole as an inhibitor was evaluated using electrochemical techniques, including potentiodynamic polarization, cyclic voltammetry, and electrochemical impedance spectroscopy. According to the potentiodynamic polarization results, 2-mercapto-1-methylimidazole can be classified as a mixed-type inhibitor. The inhibition efficiency also increases with increasing concentration. The results indicate that the Cu-Fe-P alloy has improved corrosion resistance compared to copper, and a higher inhibition efficiency of 2-mercapto-1-methylimidazole was observed for the Cu alloy. Full article

Seismic-resistant reinforcing steels play a key role in structures subjected to earthquake loading, requiring an optimal balance between strength, ductility, and weldability. Microalloying with vanadium (V), niobium (Nb), and titanium (Ti) is widely used to improve these properties through precipitation strengthening and grain refinement. This work aims to contribute to the development of seismic-resistant reinforcing steels for the Moroccan construction sector. A literature review identified key international requirements, including a tensile-to-yield strength ratio (Rm/Re) of 1.15–1.35 and a total elongation at maximum force (Agt ≥ 7%). In parallel, Moroccan reinforcing bars were mechanically and microstructurally characterized. A conventional steel containing 0.65 wt.% Mn and no vanadium was used as a reference. This steel exhibited limited strain-hardening capacity, with Rm/Re ratios between 1.12 and 1.15. To improve this behavior, steels containing 1.1 wt.% Mn with different vanadium additions were investigated. Preliminary results indicate that vanadium microalloying improves mechanical performance through combined precipitation strengthening and ferrite grain refinement. The increase in strength is likely associated with fine V(C,N) precipitates formed during cooling, while ferrite grain refinement appears to contribute to maintaining ductility. This synergistic effect results in a more favorable strength–ductility balance, supporting the development of seismic-resistant reinforcing steels for structural applications. Full article

This paper reviews recent advances in additive manufacturing (AM) of aluminum alloys and proposes an integrated framework of materials, processes, microstructure, properties, and applications. Focusing on Laser Powder Bed Fusion (L-PBF) and Directed Energy Deposition (DED), it summarizes the major challenges of aluminum alloy AM, including hot cracking, porosity, and anisotropy, together with corresponding optimization strategies. The paper particularly highlights three additive manufacturing-specific alloy systems—Sc/Zr microalloyed, heat-resistant eutectic, and transition-metal-strengthened aluminum alloys—and clarifies their composition design and strengthening mechanisms. Finally, future trends in intelligent manufacturing, integrated alloy process design, and green development are discussed, emphasizing the importance of interdisciplinary integration for large-scale industrial applications. Full article

Sulfur-containing medium-carbon microalloyed steel blooms are widely used for high-load automotive components, and reducing surface defects is important for improving product yield and lowering downstream processing costs. To address surface defects such as star cracks and microcracks in the continuous casting of these steel blooms, this study redesigned the mold flux on the basis of the steel’s solidification characteristics and crack susceptibility and carried out a twin-strand industrial comparative casting trial. Thermodynamic and thermophysical analyses indicated that the relatively high contents of S, Mn, and Ti/N in the steel promoted the precipitation of MnS and TiN–MnS complex inclusions along grain boundaries, severely weakening grain boundary cohesion. Meanwhile, the high specific heat capacity and low thermal conductivity further intensified thermal stress concentration in the solidifying shell, rendering the steel highly susceptible to cracking. Evaluation of the originally used mold flux (Flux A) revealed that its high melting temperature (1189 °C), long melting time (106 s), high break temperature (1170 °C), and poor crystallization behavior resulted in an excessively thin liquid slag layer (<5 mm) within the mold, making it difficult to provide adequate lubrication and stable heat transfer; these were key external factors inducing surface defects. Accordingly, the optimized mold flux (Flux B) was designed and prepared by increasing the basicity from 0.95 to 1.1, raising the Al₂O₃ content from 9.48% to 11.16%, increasing the F content from 4.93% to 5.58%, and reducing the carbon content from 13.85% to 6.97%. The rheological and crystallization properties of the flux were optimized in a coordinated manner, allowing uniform heat transfer through the crystalline slag layer while maintaining adequate lubrication. Industrial comparative trials demonstrated that Flux B stabilized the liquid slag layer at 8–10 mm, increased slag consumption to 0.56 kg/t, and significantly reduced surface defects such as star cracks and microcracks on blooms. The ultrasonic testing acceptance rate for rolled products increased to 98.6%, thereby meeting stringent quality requirements for the continuous casting of sulfur-containing, medium-carbon, microalloyed steel blooms. Full article

Hydrogen embrittlement is a critical degradation mechanism in microalloyed and pipeline steels used in hydrogen-economy infrastructure. We present a physics-informed neural network (PINN) framework that embeds Fick’s second law and the Arrhenius temperature dependence directly into the loss function, trained on 22 temperature-dependent data points spanning pure α-Fe and API X65 pipeline steels (modern and vintage microstructures). The PINN recovered the pure-iron activation energy (4.2 kJ mol⁻¹ vs. literature 4.15 kJ mol⁻¹, R² = 1.00) and yielded Arrhenius activation energies of 28.5 and 45.2 kJ mol⁻¹ for modern and vintage X65, respectively, indicating substantially stronger trapping in older microstructures. McNabb–Foster analysis of ten ternary Fe–Me–C,N alloys revealed flat-trap binding enthalpies of 19 ± 2 kJ mol⁻¹ and deep-trap free energies of 57 ± 2 kJ mol⁻¹, with effective diffusivities spanning three orders of magnitude governed primarily by flat-trap density. The framework provides a computationally efficient and physically consistent tool for hydrogen transport prediction, with a clear roadmap for multi-feature extension incorporating compositional and microstructural descriptors. Full article

The effects of Ti/Nb microalloying-induced MC-type carbide precipitation and tempered microstructure evolution on the dry-sliding wear behavior of low-carbon martensitic wear-resistant steels were systematically investigated. Three experimental steels with different microalloying strategies (0.04Ti, 0.1Ti, and 0.04Ti/Nb) were subjected to quenching and subsequent tempering. Microstructural features, carbide characteristics, and mechanical properties were characterized using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), tensile testing, and impact testing, while wear performance was evaluated by pin-on-disk tests under dry-sliding conditions. The results indicate that wear resistance is governed by the combined effects of tempered martensite stability and MC-type carbide precipitation. Low-temperature tempering effectively reduces the wear mass loss of Ti-containing steels by enhancing their resistance to abrasive shear deformation while maintaining sufficient toughness. In contrast, the Nb-containing steel exhibits a stage-dependent wear response associated with the formation and destabilization of oxide-derived third-body debris during sliding. (Nb,Ti)C precipitates act as microscale load-bearing units, contributing to strength enhancement and subsurface damage suppression, but their influence on wear behavior strongly depends on tempering temperature. The dominant wear mechanism is abrasive micro-cutting, accompanied by fatigue-induced spalling and oxidation-assisted damage at later stages. These results demonstrate that wear performance cannot be correlated with hardness alone, but instead requires the coordinated optimization of carbide precipitation and tempered microstructural stability. This work provides microstructural guidance for the design of microalloyed martensitic wear-resistant steels. Full article

To address the strength fluctuation observed in Ti microalloyed steel, the effects of final rolling temperature, coiling temperature, and Ti content on the microstructure, secondary phase precipitation behavior, and grain size were investigated through simulation experiments. Various characterization techniques were employed to elucidate the underlying causes of the strength variation, and key control strategies were proposed. The results indicate that the strength fluctuation is primarily influenced by the presence of nano-sized TiC precipitates. The precipitation behavior of TiC can be effectively controlled by adjusting the content of non-metallic elements as well as the final rolling and coiling temperatures. Higher final rolling temperatures combined with appropriate coiling temperatures promote increased TiC precipitation; however, excessively high temperatures may result in grain coarsening and inhomogeneous precipitate distribution. The optimal processing parameters were determined to be a final rolling temperature of 860 °C and a coiling temperature of 600 °C. Full article

A systematic investigation was conducted on the effects of Cr alloying on the tensile behavior and microstructural evolution of TiZrNb medium-entropy alloys at 673 K. For comparison, the influences of Al and Cu alloying on the mechanical properties of TiZrNb were also examined. Although Al and Cu alloying enhanced the ultimate tensile strength at room temperature, their improvements in strength and ductility at 673 K were limited. In contrast, the TiZrNb_98.5Cr_1.5 alloy retained a single body-centered cubic (BCC) phase without forming the conventionally expected Laves phase. Cr effectively suppressed the formation of Zr-rich precipitates. At a strain rate of 1.67 × 10⁻³ s⁻¹ and 673 K, TiZrNb_98.5Cr_1.5 exhibits an increase in the ultimate tensile strength of approximately 408 MPa compared with the base TiZrNb alloy, while the fracture elongation increases from 10% to 25% and the threshold stress rises from 669 MPa to 1196 MPa, achieving a markedly improved strength–ductility synergy. These results indicate that Cr alloying effectively stabilizes the microstructure and enhances the mechanical performance of TiZrNb alloys at 673 K by suppressing precipitate formation and reducing dislocation accumulation, outperforming Al and Cu alloying at the same temperature. Full article

The influence of Cu content on the thermal conductivity and mechanical properties of Al-9Si-0.7Fe casting alloy were investigated in this paper. The results show that as the Cu content increases from 0.1 wt.% to 2.0 wt.%, the thermal conductivity of the alloy decreases from 173.6 W/(m·K) to 154.8 W/(m·K), while the yield strength increases from 72.2 MPa to 90.9 MPa. Metallographic, XRD, and EPMA analyses revealed that Cu has a relatively small impact on the secondary dendrite arm spacing of α-Al and the morphology of eutectic silicon. Its influence on the thermal conductivity and mechanical properties primarily stems from Cu atoms dissolving in the α-Al matrix, leading to a decreased lattice constant, increased lattice distortion, enhanced electron scattering, and improved solid solution strengthening effect. Based on the measured solubility of Cu, the Maxwell and Hashin–Shtrikman thermal conductivity models were modified. The correlation coefficients between the predicted values of the modified models and the experimental data were 92.77% and 93.11%, respectively, indicating a significant improvement in prediction accuracy. Full article

This study investigates the 55%Al-Zn-Si coating system. Using microstructural characterization and thermodynamic simulation, we systematically analyzed its microstructure formation, solidification behavior, and the regulatory effects of Cr, Nb, and V micro-alloying elements. The results show that the typical coating consists of a primary α-Al dendritic skeleton and an interdendritic Zn-rich eutectic phase, exhibiting a characteristic spangle morphology. The addition of Si is crucial. By participating in the formation of a Fe-Al-Si ternary compound layer, it effectively suppresses the intense reaction at the Fe/Al interface, providing essential conditions for the sufficient growth of the outer Al-rich dendrites and the formation of a continuous transition layer. Thermodynamic analysis further clarifies that the coating solidification follows three distinct stages: precipitation of the primary α-Al phase, an Al-Si binary eutectic reaction, and a final Al-Zn-Si ternary eutectic transformation. Regarding micro-alloying, this study reveals the specific roles of different elements: Cr significantly refines the transition layer structure, promoting its transformation from coarse lamellae into a fine and uniform morphology; V tends to combine with Al to form high-melting-point enriched regions, inhibiting the growth of Fe-Al intermetallics and reducing the thickness of the brittle transition layer by approximately 50%; conversely, the addition of Nb disrupts the normal solidification sequence, inducing abnormal segregation of Al-rich and Si-rich phases, which compromises the homogeneity and integrity of the coating structure. Through an in-depth analysis of the fundamental solidification mechanism and micro-alloying effects, this research provides an important theoretical basis for optimizing the microstructure of hot-dip Al-Zn sheets via precise composition design and micro-alloying strategies. Full article

Despite the crucial role of Young’s modulus in the structural performance of Al alloys, the effects of common strengthening approaches on its evolution, particularly at elevated temperatures, remain largely unexplored. In this study, an Al-7Si-4Cu alloy was modified by hot deformation, micro-alloying with 0.3 wt.% Sc, alloying with 4 wt.% Ni, and reinforcement with 0.8 vol.% Al₂O₃ nanoparticles. The effects of these strengthening approaches on the microstructure and the evolution of Young’s modulus from room temperature to 350 °C were examined. It was found that the Young’s modulus of the alloys decreased with the increase in temperature, while this tendency is much more obvious when the temperature exceeds 250 °C. The results showed that hot deformation markedly refines the α-Al grains while the Young’s modulus stays largely unchanged. The Sc addition leads to the formation of the W phase but has no significant effect on the Young’s modulus. In contrast, the addition of Ni substantially increases the Young’s modulus through the formation of Al₃CuNi intermetallic particles, with the Young’s modulus increasing from 72.15 to 76.47 GPa. With the addition of Al₂O₃ particles, the decreasing magnitude of Young’s modulus is optimized when the temperature is higher than 250 °C. This work may be referred to when designing high-modulus Al alloys by considering the utilization of various strengthening concepts. Full article

Heat-resistant Al–Zr conductors are limited by the strength–conductivity trade-off and by long aging schedules required to stabilize Al₃Zr-based precipitates. This work investigates the combined effect of scandium addition (0–0.30 wt.%) and ultrasonic treatment (UST) during melt processing on Al–0.3Zr–xSc alloys. UST was applied at 710 °C before casting; phase-equilibrium analysis and quantitative measurements of intermetallic distribution, grain size, electrical conductivity, and tensile properties were performed before and after 25 h aging. Grain refinement shows a clear Sc-dependent threshold: UST refines the Sc-free alloy to ~177 μm, whereas 0.05 wt.% Sc causes abnormal coarsening (~396 μm). Increasing Sc to 0.10–0.20 wt.% produces pronounced refinement (~110 to ~82 μm), and the refined grain structures are retained after aging. At 0.20 wt.% Sc, the aged alloy achieves >100 MPa tensile strength while recovering approximately 58% IACS (International Annealed Copper Standard). Overall, the results reveal a composition-dependent synergy between Sc microalloying and UST that enables microstructure control and an improved strength–conductivity balance, with potential to contribute to more efficient processing strategies for heat-resistant aluminum conductors. Full article