Metals and Materials International最新文献

Additive manufacturing (AM) technologies are rapidly advancing, with Laser Directed Energy Deposition (L-DED) as a key application, frequently employing Gaussian lasers as the energy source. However, materials deposited via Gaussian laser deposition often exhibit significant temperature gradients and residual stresses, leading to defects such as cracking and deformation. In this study, Ti6Al4V and WC/Ti6Al4V alloys were fabricated using circular oscillation laser deposition and compared to those produced with Gaussian laser deposition. The research results indicate that the circular oscillation laser during deposition exhibits a stirring effect on the melt pool, suppressing the formation of elongated dendrites and promoting grain refinement. Under the impact of the high-energy laser beam, partial decomposition of WC into W and C leads to the formation of TiC and W₂C interface layers at the WC/matrix boundary, resulting in strong bonding properties. Additionally, uniformly distributed unmelted WC particles in the composite material effectively impede the growth of columnar dendrites. Compared to Ti6Al4V and WC/Ti6Al4V alloys produced via Gaussian laser deposition, specimens fabricated with circular oscillating laser deposition exhibited increases in microhardness of 9% and 6%, and reductions in wear rates of 22% and 77%, respectively. The Ti6Al4V composite containing 10 wt% WC prepared by Gaussian laser deposition exhibited exemplary corrosion resistance.

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This study examines the influence of Multi-Axial Compression (MAC) and annealing on texture evolution, grain boundary behavior, and plastic anisotropy in Cu-Zn alloys. The MAC process effectively reduces the formation of dominant copper- and brass-type textures by altering the strain path, promoting a more random texture distribution and reducing anisotropy. Texture Index (TI) values show that MAC significantly brings the alloy’s texture closer to ideal isotropy. During annealing, continuous recrystallization (RX) occurs, driven by organized dislocation structures with low dislocation arrangement indication M* values, which means disorderly arranged dislocations are first annihilated. Additionally, the formation of Σ3 coincident site lattice (CSL) boundaries plays a crucial role in suppressing grain growth, leading to a stable microstructure. The reduction in plastic anisotropy is confirmed by tensile test results, while conventional high electrical conductivity is maintained. The combined MAC and annealing processes demonstrate a promising method for improving the formability and retaining electrical performance of Cu-Zn alloys by controlling texture evolution and plastic anisotropy.

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This work examines the microstructure characteristics, evolution processes, and mechanical properties of wire arc additive manufactured specimens using cold metal transfer-pulse advanced (CMT-PADV). An arc extinguishing process occurs when the pulse cycle shifts to the cold metal transfer (CMT) cycle, resulting in a distinct microstructure known as "regularly distributed grain bands". Under thermal influence, the equiaxed dendrites in the upper region progressively transform into equiaxed grains with a random grain orientation. The microstructural precipitation process involves the sequential formation of G.P. zones (Guinier–Preston Zones), θ″ phases, θ′ phases, and θ phases. The initial three sub-stable phases introduce lattice distortion within the matrix, thereby enhancing the strengthening effects. Due to varying temperatures and thermal cycling, the sub-stable phase's composition changes, leading to a progressive increase in mechanical properties from the top to the bottom of the specimens. The ultimate tensile strength (UTS) of the thin wall gradually increased from 293.5 to 307.7 MPa, and the yield strength (YS) gradually increased from 127.4 to 134.2 MPa; the average elongation was recorded at 16%, with negligible variations. Furthermore, the alternating distribution of coarse and fine grains results in lower longitudinal properties compared to transverse properties. Specifically, the longitudinal UTS and YS decreased to 293.7 MPa and 123 MPa, respectively, while elongation reduced to 13.1%.

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Single-pass isothermal compression experiments for a duplex-phase titanium alloy (Ti–10V–5Al–2.5Fe–0.1B alloy) at 800–920 °C and strain rate of 0.0005–0.05 s⁻¹ were carried out. A dynamic recrystallization (DRX) grain identification method based on the optimized random forest model by sparrow search algorithm (SSA-RF) was used to identify DRX grains in the microstructure and realize the prediction of the degree of DRX in the microstructure under the new parameters. To verify the predictive ability of the SSA-RF model, the Extreme Gradient Boosting (XGBoost) model is introduced to identify DRX grains, and the prediction results are compared with those of the SSA-RF model. After statistically calculating the identified DRX grains, the research results show that the average relative absolute errors between the true and predicted values for DRX fraction and average DRX grain size are 9.43% and 14.04%, respectively, which are lower than those of the XGBoost model. The SSA-RF model has a higher precision in identifying DRX grains and predicting the degree of DRX at the new process parameters. In order to realize the prediction of DRX degree under new process parameters without experimental data, new data was constructed as the predicting data for the SSA-RF model based on the average grain size and the average length–diameter ratio data predicted by the SSA-RF model. The predicted results show that the errors between the predicted and true values for average DRX grain size and DRX fraction are 4.21 μm and 15.53%, respectively. The predicted results give a good indication of the true degree of DRX.

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A copper-doped fluorohydroxyapatite (Cu-FHAp) coating was successfully electrodeposited onto anodized and non-anodized AZ31 alloy using a pulse-reverse method combined with ultrasonic agitation. The effects of anodizing and ultrasonic agitation on the performance characteristics of the Cu-FHAp coating deposited on the AZ31 magnesium alloy surface were studied. The results reveal that ultrasonication reduces coating thickness while enhancing uniformity and density. Anodizing increases roughness and diminishes hydrophobicity. Coatings produced under ultrasonic conditions displayed reduced hydrophobicity and improved cell attachment but lower corrosion resistance. In contrast, coatings formed on anodized alloys through stirring achieved optimal characteristics, benefiting from the protective properties of interlayer MgO.

This study investigated the formation of intermetallic compounds (IMCs) at the carbon steel (EN31)-aluminium (AA4043) interface, focusing on the influence of variable heat input on the intermetallic thickness (IMT), element diffusion, phase transformation, texture orientation and mechanical behavior. The research showed that a high current of 36 A and a low traverse speed of 13 mm/s result in a maximum IMT of 7.7 μm due to a significant heat input of 48 J/mm, promoting extensive iron (Fe) and aluminium (Al) diffusion. The Fe-Al interface predominantly consisted of binary IMC phases such as FeAl-B2, FeAl₂, and Fe₂Al₅, as well as ternary IMC phases like Al₂Fe₃Si₄, Al₂(Fe, Si)₃, and FeSi₂Al₃. FeAl grows towards the Fe side, and Fe₂Al₅ dendrites grow towards the Al side. Si in the inter-dendritic liquid Al triggered the sequence L→L + Fe₂Al₅→ L + Fe₂Al₅ + FeAl + Si → Fe₂Al₅ + FeAl + FeSi₂Al₃. Higher elastic modulus (E) and phase hardness (H) values of the bimetallic interface were obtained with the condition where the FeAl: Fe₂Al₅ ratio of 1:3 and an IMT of less than 4 μm are fulfilled, and it generally occurred at the lower heat input (≤ 43 J/mm). The results indicated that the interface developed at 43 J/mm has superior strength, reaching up to 73 MPa, 54% higher than the high heat input sample. However, the poor elongation suggested extreme brittleness due to continuous IMCs. Further research is needed to optimize interface characteristics by controlling the cooling rate, especially for cyclic and severe tensile loads applications.

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This study presents a novel model for evaluating non-equi-biaxial surface residual stresses in metals using surface in-plane displacements around an indentation, as an alternative to the commonly used instrumented force-depth curve. The surface X- and Y-displacements are measured within an annular region around the indentation imprint by Digital Image Correlation with random patterns generated from surface scratches. Integration of these displacements allows for evaluating principal residual stress magnitudes and directions by comparing the results from stressed and stress-free specimens. The effects of stress state and material property were investigated within a series of finite element simulations, and an alternative way was developed to eliminate the need for stress-free specimens. Experimental validation was conducted on specimens with known non-equi-biaxial stress states.

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New ternary eutectic aluminum alloys, namely Al–6Ca–3Ce, Al–6Ca–3La, and Al–6Ca–1Fe (wt%) were studied in as-cast state as well as after the high-pressure torsion (HPT) processing and subsequent annealing. It was found that HPT (3 revolutions) formed a nanocrystalline grain/subgrain microstructure or a mixed nano- and submicrocrystalline grain/subgrain microstructure. Moreover, the numerous eutectic particles were refined down to the nanometer range, which led to the formation of multiple stress concentrators and embrittlement of the material. To improve ductility of the alloys, annealing treatment was used. It was shown that annealing at 350 °C (1 h) after HPT resulted in the multiple grain/subgrain growth and predominantly equiaxed grain microstructure formation in all alloys, as well as in the coarsening of some eutectic particles. This caused a decrease in stress concentration. As a result, the strength of the alloy increased and its ductility was restored. The ultimate tensile strength of the Al–6Ca–3Ce, Al–6Ca–3La, and Al–6Ca–1Fe alloys was 455, 422, and 377 MPa, respectively, which was 3.5, 2.2, and 2 times greater than in the as-cast alloys. The relative elongation of the Al–6Ca–3Ce, Al–6Ca–3La, and Al–6Ca–1Fe alloys was 2, 18, and 9%, respectively. Lanthanum, being part of the complex eutectic Al₄(Ca, La), ensured high ductility of the alloy, both in the cast state and in the deformed and heat-treated state.

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The relatively low creep resistance of magnesium (Mg) alloys limits their application in high-temperature environments. Mg-Gd-based alloys, however, exhibit exceptional creep resistance, making them promising candidates for such applications. This review comprehensively examines recent advancements in the characterization and optimization of Mg-Gd-based alloys, focusing on key factors influencing their creep resistance. Key strategies for improving creep resistance include precise composition optimization with rare-earth elements such as Y and Nd, combined with Zn, Ca, Mn, and Al elements to alter precipitation behavior and enhance thermal stability. Thermomechanical processing has emerged as a critical tool to further improve creep resistance by tailoring grain structure and precipitation states. Furthermore, the review highlights the integration of machine learning to predict and design creep-resistant alloys, enabling cost-effective and accelerated development pathways. The discussion extends to future perspectives in optimizing Mg-Gd-based alloys for diverse industrial applications. This work serves as a detailed guideline for researchers and engineers aiming to advance the field of high-temperature Mg alloy development.

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