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Precipitation strengthening plays a vital role in enhancing the mechanical properties of metallic materials, typically achieved through heat treatment. However, deformation-induced precipitation (DIP) in multicomponent alloys (MAs) without the assistance of annealing is rarely reported, owing to their inherent high entropy and sluggish diffusion effects. This work reveals the significant formation of nanoscale and microscale precipitates in the dual-phase Fe49.3Co23Ni23C0.85Mn1Si2.85 MA triggered by surface severe plastic deformation (SSPD) through industrial shot blasting. The SSPD process leads to the formation of ultrafine gradient structures comprising nanocrystalline and submicron-crystalline zones. Submicron SiO2 precipitates emerge at the interfaces of both these zones, while various Mn5Si3 and Si nanoparticles precipitate within the nanocrystalline zone. This phenomenon can be ascribed to the high density of generated substructures, the accelerated diffusion of atoms, and the reduction in solid solubility limits in the SPD-driven non-equilibrium state.

In the context of the growing research interest in multi-component alloys (MAs) and their exceptional performance under extreme environments, the high-temperature oxidation resistance and applications of MAs have attracted significant attention in the field of metallic materials. While the cost-effective and mechanical properties of Co-free MAs are of great importance, their oxidation resistance remains insufficiently understood. In this work, we designed multiple heterogeneous structures within a cast dual-phase Cr30Fe30Ni30Al5Ti5 MA by tailoring the Al and Ti ratio, which consists of body-centered-cubic (BCC) grains reinforced by multi-scale nanoprecipitates (i.e., L21, B2, and η phase) and an L12-strengthened face-centered cubic (FCC) skeleton. Isothermal oxidation experiments at 800 °C, 1000 °C, and 1200 °C with varying exposure durations were conducted. The oxidation kinetics at 800 °C and 1000 °C followed a parabolic law, while both low weight increment and oxidation rate confirm remarkable oxidation resistance. At 800 °C, the oxides mainly consist of Cr2O3 and Al2O3, while are dominated by (TiO2 + Cr2O3) and the mixed oxides of Al2O3, TiO2, and Ti2O above 1000 °C. Importantly, the inability to form a continuous Al2O3 oxide scale at higher temperatures led to a deterioration in oxidation resistance. These findings offer valuable insights into underlying mechanisms contributing to oxidation resistance for Co-free MAs.

High-entropy alloys (HEAs) have attracted considerable attention for their exceptional microstructures and properties. Discovering new HEAs with desirable properties is crucial, but traditional design methods are laborious and time-consuming. Fortunately, the emerging Machine Learning (ML) offers an efficient solution. In this study, composition-microhardness data pairs from various alloy systems were collected and expanded using a Generative Adversarial Network (GAN). These data pairs were converted into empirical parameter-microhardness pairs. Then Active Learning (AL) was employed to screen the Al-Co-Cr-Cu-Fe-Ni system and identify the eXtreme Gradient Boosting (XGBoost) as the optimal ML master model. Millions of data training iterations employing the XGBoost sub-model and accuracy evaluations using the Expected Improvement (EI) algorithm establish the relationship between HEA compositions and microhardness. The proposed sub-model aligns well with experimental data, wherein four Al-rich compositions exhibit ultra-high microhardness (>740 HV, with a maximum of ∼780.3 HV) and low density (

Abstract Objective To introduce a new type of simple adjustable bilateral bidirectional polyvinyl chloride (PVC) tube traction device and discuss the value of using this device before surgery in patients with lower limb fractures. Methods To introduce the manufacturing process of an adjustable bilateral traction device made of PVC pipes. From August 2018 to November 2019, the data of 36 patients with lower limb fractures who were treated with this traction device were retrospectively analysed. The treatment outcomes were analysed, including length of both lower limbs, fracture reduction, lower limb mobility, visual analogue scale (VAS) score, incidence of complications, and patient satisfaction. Results All patients were able to move the affected limb immediately after using the device. The patient's pain was significantly reduced, they were able to turn over freely during bed rest, and the length of the affected limb was restored to that of the healthy limb. Thirty-four (94.5%) patients were satisfied with the reduction of the fracture end, 2 (5.5%) patients with tibiofibular fractures showed angular displacement of the fractured end and satisfactory reduction after the position of the bone traction needle was adjusted; 7 (19.5%) patients developed deep vein thrombosis of the affected lower limb during traction; there was no decubitus or vascular nerve injury, and the overall complication rate was 25% (9/36). All the patients and their families were satisfied with the results of this treatment. Conclusion The aim of this study is to introduce a new type of traction device. It is advantageous in that it is light weight, low cost, easy to assemble, promotes immediate movement of the affected limb after assembly, improves patient comfort and can be used with a titanium steel needle for MRI examination under traction. In the clinical setting, it has been shown to be suitable for the temporary treatment of patients with lower leg fractures prior to surgery, particularly patients who, for various reasons, require nonsurgical treatment in the short term.

In this work, a new design principle, i.e. doping with refractory metal particles with a low diffusion rate to prevent the formation of cracks and to improve the mechanical properties of bulk metallic glass (BMG) composites, was put forward. It was proven that crack-free and dense Mo(p)/Cu47Zr47Al6 BMG composites with enhanced mechanical properties can be produced via LPBF. The dislocations generated in the Mo particles can release thermal stress, thereby inhibiting the formation of thermal-cracks. The fracture patterns of Mo particles show that they can delay rapid of crack expansion, thereby improving the inherent strength and toughness of the material.

Recent investigations have demonstrated that the plasticity of bulk metallic glasses (BMGs) at room temperature can be improved by artificially introducing both macroscopic and microscopic defects. In this work, both surface grooves and multiple shear bands (MLSBs) are concurrently introduced into the surface of a Zr65Cu15Ni10Al10 BMG employing an ultrasonic bonding machine, whose sizes are also tailored by tuning gas pressures and times. After surface treatment, MLSBs appear around grooves due to the pre-plastic deformation, while numerous nano-scale crystals resulting from thermal-induced nanocrystallization appear within the grooves, leading to the emergence of hierarchical structural heterogeneities. As a result, the strength and plasticity are effectively enhanced compared to as-cast samples when suitable experimental parameters are adopted. The plastic deformation mechanisms change from single main shear banding to multiple shear banding. Therefore, the serrated plastic behaviors exhibit a transition from chaotic to self-organized critical dynamics after surface treatment, confirming the modification of the shear banding instability. The present study provides a viable method to tailor the mechanical properties of BMGs and sheds light on their dynamic plastic deformation behaviors.

The glass-forming ability (GFA), thermal stability and crystallization kinetics of (Cu0.5Zr0.5)100-xFex (x = 2.5, 5, 7.5, 10 and 12.5 at.%) amorphous alloys were studied in detail. As Fe concentration increases, the GFA and thermal stability decrease first and then increase. The excessive Fe addition significantly deteriorates the GFA due to the precipitation of the FeZr2 phase. Interestingly, with increasing Fe concentration, the crystallization products gradually transit from Cu10Zr7 and CuZr2 to B2 CuZr phase, indicating that Fe addition can effectively enhance the thermal stability of B2 phase. Simulation results show that Fe atoms may be dissolved into the B2 lattice substituting Cu sites and decrease the formation energy, which is similar to Co–or Zn-added CuZr-based alloys. Non-isothermal crystallization behaviors of Cu–Zr–Fe amorphous alloys are well described by the Šesták-Berggren (SB) model instead of the John-Mehl-Avrami (JMA) model due to the multi-phase formation (low Fe concentration) or the nucleation and growth of B2 phase (high Fe concentration). These results could help with the understanding of further stabilizing B2 CuZr phase and the fabrication of high-performance CuZr-based composites.

Al1.8CrCuFeNi2 high-entropy alloy coatings with different TiC contents were prepared using laser cladding. The effect of TiC on the microstructure, hardness and wear resistance of the coatings was investigated. It was found that the phase structure of the coating with 10 wt.% TiC was a single BCC phase with no other precipitated phase. When 20 wt.% TiC was added, the phase structure of the coating was a BCC phase and TiC phase. When the TiC content increased to 30 wt.%, more TiC-reinforcing phase was formed. With the increase in the TiC content, the hardness of the high-entropy alloy coating was enhanced and the wear loss clearly decreased, which was closely related to the change in the coating structure. The addition of TiC to high-entropy alloys plays the role of fine-grain strengthening and dispersion strengthening.

Denoising plays an important role in the Magnetic Resonance Imaging (MRI) applications for medical diagnosis. MRI images usually contain undesired noises which would negatively affect the exactitude of pathological diagnosis. Recently, many models for MRI denoising have been developed from deep learning networks. In this paper, we propose a novel MRI image denoising method using the conditional Generative Adversarial Networks (GANs). Specifically, a Convolutional Neural Network (CNN) is utilized as the discriminator in the process to distinguish whether the image pair obtained from the conditional GAN is a real pair which consists of a noisy image and a noise-free image or a fake pair which, on the other hand, contains a noisy image and a denoised image. In our design, the convolutional encoder-decoder networks-based generator is used to remove the noise in the noisy MRI images as much as possible. The whole architecture is trained by adversarial learning. Experiments using both synthetic and real clinical MRI datasets are conducted. When tested on the synthetic T1w images with 10% noise level, our method performed better in terms of reaching a high structural similarity index (SSIM) at 0.9489 while that of the next best method was only 0.7485. Moreover, when the image noise level was increased from 1% to 10%, our method was more stable that the SSIM only dropped about 3.2% while that of the next best method dropped about 23.7%. Simulation results demonstrate that the proposed method is more robust and outperforms the conventional methods in both the denoising level and preservation of the anatomical structures and defined contrast.

Pre-plastic deformation (PPD) treatments on bulk metallic glasses (BMGs) have previously been shown to be helpful in producing multiple shear bands. In this work, the applicability of the PPD approach on BMGs with different Poisson’s ratios was validated based on experimental and simulation observations. It was found that for BMGs with high Poisson’s ratios (HBMGs, e.g., Zr56Co28Al16 and Zr46Cu46Al8), the PPD treatment can easily trigger a pair of large plastic deformation zones consisting of multiple shear bands. These PPD-treated HBMGs clearly display improved strength and compressive plasticity. On the other hand, the mechanical properties of BMGs with low Poisson’s ratios (LBMG, e.g., Fe48Cr15Mo14Y2C15B6) become worse due to a few shear bands and micro-cracks in extremely small plastic deformation zones. Additionally, for the PPD-treated HBMGs with similar high Poisson’s ratios, the Zr56Co28Al16 BMG exhibits much larger plasticity than the Zr46Cu46Al8 BMG. This phenomenon is mainly due to more defective icosahedral clusters in the Zr56Co28Al16 BMG, which can serve as nucleation sites for shear transformation zones (STZs) during subsequent deformation. The present study may provide a basis for understanding the plastic deformation mechanism of BMGs.

One way to rejuvenate metallic glasses is to increase their free volume. Here, by randomly removing atoms from the glass matrix, free volume is homogeneously generated in metallic glasses, and glassy states with different degrees of rejuvenation are designed and further mechanically tested. We find that the free volume in the rejuvenated glasses can be annihilated under tensile or compressive deformation that consequently leads to structural relaxation and strain-hardening. Additionally, the deformation mechanism of highly rejuvenated metallic glasses during the uniaxial loading–unloading tensile tests is investigated, in order to provide a systematic understanding of the relaxation and strain-hardening relationship. The observed strain-hardening in the highly rejuvenated metallic glasses corresponds to stress-driven structural and residual stress relaxation during cycling deformation. Nevertheless, the rejuvenated metallic glasses relax to a more stable state but could not recover their initial as-cast state.

Semantic-based image retrieval plays an important role in many practical applications, which aims to look for images with similar contents. Extracting discriminative representations of images is the real crux of this task. Directly utilizing the results of fully connected layers of convolutional neural networks (CNNs) is one of the best feature extraction methods. However, the fully connected layer is only supervised by the softmax loss, which only aims to maximize the accuracy of object classification and hardly pays attention to the spatial distribution of features, especially the intra-class and inter-class feature distances which are of great importance in semantic-based image retrieval. To compensate the performance degradation due to this reason, we try to address the spatial distribution of the features by two different loss functions. The first loss function jointly combines the softmax loss and the center loss in the training of the CNNs, which simultaneously ensures that the features of images with different contents are separable and the features of images in the same class are close. The second loss function is defined as an improved center loss which not only penalizes the distance between the obtained deep feature and the feature center of its own class, but also encourages a far distance between the feature and the feature centers of any other classes. We have conducted experiments on both ILSVRC data set and Caltech256 data set, demonstrated that the deep features got by our approaches can achieve better performance than other methods in semantic-based image retrieval, and the improved center loss can further outperform the joint supervision of the softmax loss and the center loss.

The microstructures and mechanical properties of (Cu0.5Zr0.5)100−xZnx (x = 0, 1.5, 2.5, 4.5, 7, 10, and 14 at. %) bulk metallic glass (BMG) composites were studied. CuZr martensitic crystals together with minor B2 CuZr and amorphous phases dominate the microstructures of the as-quenched samples with low Zn additions (x = 0, 1.5, and 2.5 at. %), while B2 CuZr and amorphous phases being accompanied with minor martensitic crystals form at a higher Zn content (x = 4.5, 7, 10, and 14 at. %). The fabricated Cu-Zr-Zn BMG composites exhibit macroscopically appreciable compressive plastic strain and obvious work-hardening due to the formation of multiple shear bands and the deformation-induced martensitic transformation (MT) within B2 crystals. The present BMG composites could be a good candidate as high-performance structural materials.

An experimental study with respect to the effect of an alternating electropulsing on grain refinement in pure aluminum was reported. The macrostructural observation with the mold preheated to different temperature and embedded the metal mesh indicated that the change of electric current-associated free energy related with the position of crystal nuclei (ΔGem) and forced convection dominated the generation of fine equiaxed grains (FEG). Under electropulsing with 480 A, ΔGem induced the dissociation of crystal nuclei from the upper interface of the electrode and the melt, leading to the generation of FEG. For a larger current intensity, FEG originated from the dissociation of crystal nuclei on the side wall besides the upper interface due to ΔGem and the forced convection. Furthermore, the model coupling the dissociation of crystal nuclei and dendrite fragmentation due to the forced convection and the dissociation of crystal nuclei due to ΔGem was presented to explain the formation mechanism of FEG in pure aluminum under electropulsing.

The effect of direct current (DC) on the wetting behavior of Cu substrate by liquid Ga–25In–13Sn alloy at room temperature is investigated using a sessile drop method. It is found that there is a critical value for current intensity, below which the decrease of contact angle with increasing current intensity is approximately linear and above which contact angle tends to a stable value from drop shape. Current polarity is a negligible factor in the observed trend. Additionally, the observed change in contact angles is translated into the corresponding change in solid-liquid interfacial tension using the equation of state for liquid interfacial tensions. The solid-liquid interfacial tension decreases under DC. DC-induced promotion of solute diffusion coefficient is likely to play an important role in determining the wettability and solid-liquid interfacial tension under DC.

In this work, the microstructural evolution and magnetic performance of the melt-spun amorphous and amorphous-crystalline Fe26.7Co26.7Ni26.7Si8.9B11.0 high-entropy alloys (HEAs) during crystallization were investigated, respectively. Upon heating fully amorphous ribbons, a metastable BCC supersaturated solid solution together with a little Ni31Si12 crystals first precipitated and then the (Fe,Co)2B crystals formed until the full crystallization was achieved. With further increasing temperature after full crystallization, a polymorphic transformation from a metastable BCC phase to two types of FCC solid solutions occurred. For the amorphous-crystalline HEAs, the dominant crystallization products were the metastable FCC but not BCC crystals. During crystallization, the primary metastable FCC crystals first transform into the metastable BCC crystals and then the newly-generated BCC phase transforms into two types of FCC phases with further increasing temperature. This temperature dependence of the gradual polymorphic transformation results in the change of magnetic properties of the present high-entropy amorphous alloys.

In this study, the microstructural evolution and mechanical properties of TiCuNiZr-based bulk metallic glass (BMGs) composites were systematically investigated in order to optimize both the strength and the ductility of BMGs. By tailoring the glass-forming compositions, TiCuNiZr-based BMG composites with different volume fractions of B2 (Ti,Zr)(Cu,Ni) crystals precipitating in the glassy matrix exhibit not only macroscopic ductility but also high strength as well as work-hardening, which is due to the formation of multiple shear bands and martensitic transformation during deformation. Optimized mechanical properties can be achieved when the crystalline volume fraction is at least higher than 44 vol. %, which is attributed to the sizeable difference between Young’s moduli of the B2 (Ti,Zr)(Cu,Ni) crystals and the glassy matrix, and the precipitation of Ti2Cu intermetallic compounds at the B2 crystal boundaries. Our study provides a complementary understanding of how to tailor mechanical properties of TiCu-based BMG composites.

In recent years, CuZr-based bulk metallic glass (BMG) composites ductilized by a shape memory B2 CuZr phase have attracted great attention owing to their outstanding mechanical properties. However, the B2 CuZr phase for most CuZr-based glass-forming compositions is only stable at very high temperatures, leading to the uncontrollable formation of B2 crystals during quenching. In this work, by introducing Co (i.e., 4, 5, and 6 at. %) and 10 at. % Al into CuZr-based alloys, the relatively good glass-forming ability (GFA) of CuZr-based alloys still can be achieved. Meanwhile, the B2 phase can be successfully stabilized to lower temperatures than the final temperatures of crystallization upon heating CuZr-based BMGs. Unlike previous reported CuZr-based BMGs, the primary crystallization products upon heating are mainly B2 CuZr crystals but not CuZr2 and Cu10Zr7 crystals. Furthermore, the primary precipitates during solidification are still dominated by B2 crystals, whose percolation threshold is detected to lie between 10 ± 2 vol. % and 31 ± 2 vol. %. The crystallization kinetics underlying the precipitation of B2 crystals was also investigated. Our results show that the present glass-forming composites are promising candidates for the fabrication of ductile CuZr-based BMG composites.

Microstructures and mechanical properties of as-cast Cu47.5Zr47.5Al5 bulk metallic glass composites are optimized by appropriate remelting treatment of master alloys. With increasing remelting time, the alloys exhibit homogenized size and distribution of in situ formed B2 CuZr crystals. Pronounced tensile ductility of ∼13.6% and work-hardening ability are obtained for the composite with optimized microstructure. The effect of remelting treatment is attributed to the suppressed heterogeneous nucleation and growth of the crystalline phase from undercooled liquid, which may originate from the dissolution of oxides and nitrides as well as from the micro-scale homogenization of the melt.

Herein, the L12-strengthened Co34Cr32Ni27Al3.5Ti3.5 medium-entropy alloy (MEA) with outstanding strength and ductility is developed through cold rolling and annealing (CRA). The CRA promotes the formation of coherent L12 nanoprecipitates in the matrix and precipitates inside the grains (Ti-rich phases), resulting in dislocation sliding and multiplication during deformation. The as-cast sample exhibits low yield strength (YS) of ≈498.5MPa, ultimate tensile strength (UTS) of ≈820.5MPa, and uniform elongation (UE) of ≈29.8%. After cold rolling and annealing, the YS, UTS, and UE are significantly increased to ≈678.4, ≈1109.3MPa, and ≈44.5%, respectively. The excellent mechanical performance results from dislocation strengthening and precipitation strengthening of the L12 phase. The trade-off of strength-ductility is resolved by achieving an appropriate balance between the hard phase rich in L12/Ti and the soft face-centered cubic phase. This finding demonstrates that the CRA method can be used to create coherent L12 nanoprecipitates that are beneficial for strong and ductile MEA. This work provides a broader perspective for CoCrNi-based MEAs with high performance in the future. [ABSTRACT FROM AUTHOR]