Metals and Materials International最新文献

To investigate the influence of Ni element content on the absorptive properties of nano medium-entropy FeCoNi alloy particles, five groups of nano medium-entropy FeCoNi alloy particles was synthesized with varying Ni element contents by chemical liquid-phase reduction, and the microstructure characteristics, magnetic and absorptive properties were studied. The results show that the synthesized nano medium-entropy FeCoNi alloy particles have a spherical geometry and face-centered cubic crystal structure, with a slight increase in particle size as the Ni element content increases, averaging radius 100–200 nm. The alloy particles exhibit soft magnetic properties, with decreasing saturation magnetization intensity, coercivity, and residual magnetization as the Ni element content increases. The real and imaginary parts of the dielectric constant and complex magnetic permeability of the prepared FeCoNi alloy particles show an increasing followed by a decreasing trend with the increase of Ni element content, maximum values was with Ni element content of x = 0.8. As the electromagnetic frequency increases, the real part of the complex magnetic permeability of the alloy particles follows a decreasing trend, and the imaginary part of the magnetic permeability at a Ni element content of x = 0.8 is lower than that of the other alloy particles. The dielectric loss gradually increases with the rise of electromagnetic wave frequency, with polarization relaxation was the primary loss mechanism. At a Ni element content of x = 0.8, the alloy particle sample demonstrates the widest effective absorption bandwidth 4.48 GHz with sample thickness of 1.4 mm and the maximum reflection loss 44.2 dB with thickness of 1.6 mm. Similarly, with Ni element content of x = 1, the alloy particle sample exhibits the largest effective absorption bandwidth 5.36 GHz at thickness 1.6 mm and the maximum reflection loss 32.5 dB at thickness of 1.8 mm.

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Five sets of nano medium-entropy FeCoNi alloy particles with varying Ni element contents were fabricated with chemical liquid deposition and the static magnetic characteristics with electromagnetic wave absorption performance were provided and studied. The maximum reflection loss 44.2 dB and the largest effective absorption bandwidth 5.36 GHz with thickness 1.6 mm were obtained.

The dynamic recrystallization (DRX) behavior during the thermal deformation process of AZ61 magnesium alloy was systematically studied using a combined finite element (FE) and cellular automaton (CA) model. Isothermal compression experiments on AZ61 magnesium alloy were conducted using a Gleeble-1500 thermal simulator at temperatures ranging from 300 to 450 ℃ and strain rates from 0.003 to 1 s⁻¹, obtaining true stress–strain curves under various deformation conditions. Based on the obtained experimental data, a high-precision physical constitutive model for AZ61 alloy was established, along with a DRX kinetics model and a recrystallization critical model. At the same time, the grain size model was established by measuring the microstructure of the alloy. In addition, the parameters of the CA model were found, and the dislocation density model for CA simulation was established on this basis. Simulation results indicated that the dynamic recrystallization behavior is influenced by deformation temperature, strain rate, and strain. The predicted DRX volume fraction and average grain size matched well with experimental results, with a maximum error of less than 8%, demonstrating the high accuracy of the established model. This validated the effectiveness and predictive prospect of the CA-FE coupled method, this method provides a powerful tool and theoretical guidance for studying the DRX microstructure evolution of AZ61 magnesium alloy during hot deformation.

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The model and simulation results required for DRX simulation during hot deformation of AZ61 magnesium alloy

Ti₂AlNb-based coatings with different TaC additions (0, 1.25, 2.5 and 5 at%) were prepared on Ti-6Al-4 V alloy to improve its surface properties by laser cladding. The effects of TaC addition on the morphology, microstructure transformation and mechanical properties of the laser cladding TiC/Ti₂AlNb coatings were studied. The results showed that the TiC/Ti₂AlNb coatings mainly composed of matrix B2 phase, layered O phase and a small amount of TiC. In situ formed TiC effectively refined the microstructure of the coatings. When the TaC addition increased from 0 to 5 at%, with the amount of in situ formed TiC increased from 0 to 20%, the grain size of B2 decreased from ~ 400 μm to ~ 50 μm, and the grain size of O phase decreased from ~ 3 μm to ~ 1 μm. The microhardness and wear resistance of TiC/Ti₂AlNb based coatings improved when the TaC addition increased from 0 to 2.5 at%. The average microhardness for the sample with 2.5 at% TaC addition (602.18 HV_0.5) was 1.06 times that of the sample without TaC (568.36 HV_0.5), while the wear mass loss (16.28 mg) at 25 ℃ was only 43.4% that of the sample without TaC (37.50 mg). When the samples worn at 400 ℃ and 800 ℃ for 45 min, the wear mass losses of the sample with 2.5 at% TaC addition were only 15.13 mg and 13.50 mg, which were 50.9% and 51.5% these of the sample without TaC addition, respectively. The wear mass loss of sample with 5 at%TaC addition increased up to 16.04 mg and 16.4 mg, which means the large amount coarse TiC (dendrites) and the decrease of O phase fraction lowed the wear resistance of the TiC/Ti₂AlNb coatings, though it still less than that of the Ti₂AlNb coating (29.68 mg and 26.2 mg).

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The current research work introduces a novel processing technique involving a combination of hot rolling and a direct quench and partitioning treatments to produce an ultra-high strength, low-carbon and lean-composition steel with superior mechanical properties and enhanced stretch flangeability. The methodology involves the introduction of a secondary partitioning step after a one-step direct quenching and partitioning (DQP) process. A detailed investigations on microstructures, tensile properties and stretch flangeability (using hole expansion testing) were carried out. The martensite-austenite two phase microstructure resulted in a remarkably improved product of strength and elongation (PSE, 24 GPa.%), the hole expansion ratio of 45% and a total elongation of 21.7%. It is shown that the stability of retained austenite, rather than its volume fraction, has a significant impact on the strain hardening rate, and therefore influences strength, ductility and stretch flangeability. The results indicate that tailoring retained austenite stability is essential for optimizing the mechanical performance and stretch flangeability of quenched and partitioned steels. Introducing secondary partitioning into the Q&P process provides a feasibility to achieve a large fraction of total retained austenite, (predominantly film-type, along with small-sized blocky retained austenite islands in the microstructure), which results in high-strength Q&P steels with excellent global and local formability.

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The microstructural effect on the dwell time of the TMF test, which can describe a part of the gas turbine, was studied. In out-of-phase (OP) with dwell time on a single-crystal Ni-based superalloy, the TMF life was reduced by 61.5% compared to without dwell times. Due to the introduction of dwell time, the deformation behavior transitioned from hardening to softening. During exposure at maximum temperature, stress relaxation was occurred, which meant releasing the dislocation tangle. However, the dwell time led to the topologically close-packed (TCP) phase formation and growth. In conditions with the dwell time, TCP phase particles were increased by 241% and coarsened. Also, mechanical twins, which had resistance to crack propagation, were reduced. Therefore, the introduction of dwell time led to the promotion of cracks and the loss of resistance to crack propagation.

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Aluminum profiles in the production process will inevitably appear a variety of surface defects, seriously affect the quality of products. The traditional method to detect the surface defects can not meet the actual demand, so it is of great significance to study the efficient detection method. In this paper, digital image processing methods such as rotation, flip, contrast and brightness transformation are used to increase the number of samples and simulate the complex imaging environment. An improved YOLOX-S detection model is proposed. Squeeze-and-Excitation Networks is embedded in the Cross Stage Partial module, and then SECSP module is proposed, and all CSP modules in YOLO-S are replaced with SECSP module, which improves the sensitivity of the network to the feature channel. SCYLLA-IoU loss function is used instead of IoU loss function. The improved model can improve the detection ability of small targets and the ability to resist background interference information. The mAP reaches 91.62, which is 1.82% higher than that of the basic YOLOX-S, and the detection speed reaches 58.67 frames ·s⁻¹, which can meet the real-time detection requirements. At the same time, the comparison experiment proves that the comprehensive performance of the proposed detection model is the best, and the detection accuracy and speed have reached a good balance. The ablation experiment proves that the two improved schemes can improve the detection accuracy of the network.

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A novel strategy aimed at controlling the abnormal dissolution mechanism of carbides during electropulsing is introduced, presenting a solution to the longstanding challenge of simultaneously enhancing steel strength and plasticity. Utilizing the electropulsing assisted solution (EAS) treatment, we prepared ultra-high strength steel with increased strength and plasticity at lower temperatures and in drastically reduced timeframes. The multiple strengthening mechanisms and the plasticizing mechanisms associated with multiscale microstructures are systematically discussed. Comparisons indicate that the strength and plasticity of steels treated with EAS surpass those of steels subjected to optimize conventional furnace solution treatment. Specifically, the experimental steel subjected to electropulsing assisted solution at 850 °C for 45 min showcased a maximum tensile strength of 1924.5 MPa. This impressive feat is credited to a high dislocation strengthening of 582.3 MPa and a grain refinement strengthening of 159.7 MPa. Additionally, a peak elongation-to-failure of approximately 14.2% was observed in EAS at 885 °C for 30 min. This improvement can be attributed to the activation of the slip system, coupled with an increase in the high-angle grain boundaries fraction numbers. These changes, in turn, amplify the coordinated deformation capacity, minimizing crack propagation.

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High entropy alloys (HEAs), known for their multi-principal element composition, have attracted considerable interest in light of their unique mechanical and thermal properties. Among them, the AlCoCrFeNi HEA system has shown promising characteristics, but the influence of additional alloying elements on its performance remains a crucial area of study. This comprehensive review investigates the effects of incorporating supplementary elements into the core AlCoCrFeNi system on its microstructure and various properties. Furthermore, it explores how these alterations in microstructure impact the mechanical properties, corrosion and wear behavior of the HEA, emphasizing the potential to customize these properties through strategic alloying additions. Additionally, the review examines how varying the amounts of constituent elements in the AlCoCrFeNi system, without adding additional elements, influences the microstructure and phases formed, with the help of phase diagrams. This review offers valuable insights to researchers and engineers aiming to optimize AlCoCrFeNi HEAs for specific applications.

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