Severe Distortion Research Articles

Effects of Mn on the interface bonding and mechanical properties of TiC reinforced steel matrix composites

The addition of alloying elements to the steel matrix during the preparation process can significantly affect the properties of TiC reinforced steel matrix composites. In this study, the effects of Mn on the electronic structure and crystal structure stability of Fe supercells, along with as well as the stability of the TiC/Fe(Mn) interface, were analyzed through first-principles calculations. Additionally, 8 vol% TiC/Fe–C composites were prepared through the master alloy method. The effects of Mn contents (0, 0.8, 1.2, 1.6, and 2.0 wt%) on the interface mismatch and mechanical properties of the composites were investigated. The results revealed that Mn formed a solid solution and generated a stronger Fe–Mn bond compared with the Fe–Fe bond, and no interface chemical reaction occurred. The addition of a small amount of Mn improved the interface bonding between TiC particles and the steel matrix. The TiC particles were uniformly distributed in the matrix at the grain boundaries, with only a small amount dispersed within the grains. The TiC particles and steel matrix exhibited excellent, continuous, and stable interface bonding. The addition of Mn reduced the interface mismatch between TiC particles and the matrix. As the Mn content increased, the tensile strength and elongation of the composites first increased and then decreased, while the hardness of the composites increased. The addition of 1.2 wt% Mn resulted in an increase in the tensile strength, elongation, and hardness of the composite by 1160 MPa, 7.3%, and 43 HRC, respectively. These values were 109.8%, 151.7%, and 31.1% higher than those of the composite without Mn addition. However, an excess of Mn led to severe distortion of the Fe lattice and clustering at the interface, resulting in the degradation of the mechanical properties in the composites.

FUE as the first surgical option for hair reconstruction on scalp and facial skin grafts - case report.

Post-combustion alopecia presents a complex medical challenge with implications spanning dermatological and psychiatric disorders. The use of hair transplantation has proven to be a significant improvement for this condition. However, the current management involves various techniques, each with advantages and disadvantages. Progressive skin expansions, surgical scar reduction, and skin grafts containing hair follicles yield unsatisfactory aesthetic outcomes and have limited applicability as a first-line treatment for fire victims. So far, follicular unit extraction (FUE) has proven to be one of the most versatile procedures in such cases, having the potential to restore a natural anatomical profile closely resembling the pre-traumatic appearance that led to the traumatic alopecia. Additionally, it contributes to the improvement of associated psychiatric comorbidities, facilitating proper social reintegration and enhancing overall quality of life. This report focuses on a case of post-combustion alopecia and severe facial distortion due to third-degree burns resulting in severe psychiatric comorbidities, which benefited from a proper social reintegration and improvement of the quality of life after three consecutive sessions of FUE for scalp and eyebrow hair.

Multi-View Data-Based Layover Information Compensation Method for SAR Image Mosaic

Currently, massive Synthetic Aperture Radar (SAR) images acquired from numerous SAR satellites have been widely utilized in various fields, and image mosaicking technology provides important support and assistance for these applications. The traditional mosaic method selects specific SAR images that can cover the region of interest (ROI) from redundant data to produce “One Map”. However, an SAR image suffers from severe geometric distortion, especially in mountainous areas, which inevitably reduces the utilization of mosaic image. Therefore, a multi-view data-based layover information compensation (MDLIC) method for SAR image mosaic is proposed, aiming to take full advantage of multi-view data to compensate for the missing information in the layover area of the SAR image. This is performed to improve the information content of the mosaic image and realize efficient thematic information extraction and analysis. First, the calculation of the object-space extent of all images and the division of object-space grid are completed on the basis of geometric and radiometric preprocessing. Then, according to the transformation relationship between the object-space and the image-space, the sampling rate image of each image corresponding to the object-space grid is generated, which determines the layover area and the layover degree in each image. Finally, the information compensation strategy is implemented in accordance with the sampling rate image to realize the compensation of the layover information. The feasibility and effectiveness of the MDLIC method are verified by using multiple SAR images from the Chinese Gaofen-3 01 satellite as datasets for experiments. The experimental results indicate that the MDLIC method can obtain mosaic images with richer information compared with the traditional method, while still providing satisfactory results.

On the modelling of distorted thin-walled stiffened panels via a scale reduction approach for a simplified structural stress analysis

To reduce the weight of cruise ships, the shipbuilding industry is interested in thin-walled superstructures, where the thickness of butt-welded plates in stiffened panels is under 5 mm. Compared to thick plates, thin ones can develop severe welding-induced distortions, which limit the validity of recommended early-design structural stress assessment methods. Therefore, computationally costly 3D non-linear numerical analysis must be used. For a quick and effective early design, this paper investigates on simplified computational models for thin-walled panels under uni-axial tension, considering the distortions measured on 4-mm thick, full-scale ship-deck panels. A 2D simply-supported analytical plate is shown to be sufficiently accurate (i.e., error <10%) at 150MPa for a distortion with maximum slope within 0.02rad and amplitude smaller than the thickness (t). Moreover, a 1D beam numerical analysis efficiently predicts local stresses around the butt weld when the maximum distortion amplitude is below 0.6×tmm. The distortion needs to be considered at least up to a length of half of the plate width from the weld location and can represent longitudinal profiles within 60% of the plate width. In conclusion, the early structural stress assessment of thin-walled panels can be significantly simplified, thus helping bridge the gap between complex numerical analysis and simplified analytical solutions.

Synergistic Effects of PtRhNiFeCu High Entropy Alloy Nanocatalyst for Hydrogen Evolution and Oxygen Reduction Reactions.

The unique properties of high entropy alloy (HEA) catalysts, particularly their severe lattice distortion and the synergistic effect of multiple components, endow them with exceptional multifunctional catalytic performance. Herein, it is revealed for the first time, that the ultrasmall PtRhNiFeCu HEA nanoparticles catalyst shows outstanding catalytic activity for both hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). The catalyst exhibits an impressively low overpotential of 13mV at 10mAcm-2, a Tafel slope of 29.6mVdec-1, and high mass activity of 7.6AmgPt -1 at -50mV in alkaline media, and long-term stability of at least 20h. Moreover, the catalyst also demonstrates effective catalytic activity for acidic ORR with a commendable performance of 1.23AmgPt -1, much exceeding the commercial Pt/C catalyst. Density functional theory (DFT) calculations unveil that the efficient electrocatalytic performance for HER and ORR can be primarily attributed to the synergistic effect between components tailors and optimizes the electronic structure of PtRhNiFeCu/C HEA, which not only enhances the HER activity through increasing water capture capability, decreasing energetic barrier for water dissociation, and optimizing hydrogen absorption but also initiates non-platinum active sites with high ORR activity, achieving the improved ORR performance.

GLS–MIFT: A modality invariant feature transform with global-to-local searching

Accurate image matching is the basis for many information fusion-related applications. Conventional methods fail when handling multimodal image pairs with severe nonlinear radiation distortion (NRD) and geometric transformations. To address this problem, we present an effective method, termed modality-invariant feature transform with global-to-local searching (GLS–MIFT). First, we addressed scale changes by constructing the image scale space. Then, we obtained multi-scale, multi-orientation filtering results based on first-order Gaussian steerable filters to exploit their robustness to NRD. Next, we introduced a feature response aggregation model to synthesize the filtering results to generate a feature map, and used it to detect highly repeatable features. Additionally, we designed an adaptive partitioning descriptor to achieve rotation-invariant feature description, involving the following six steps: generation of statistical histograms of multi-orientation filtering values, synthesis of histograms on multiple scales, estimation and updating of the primary direction, determination of the sampling direction, normalization of the feature vector in sub-regions, and finally, obtaining the complete description vector. A convolutional image grouping strategy was used to enhance the rotational invariance of the method. We developed a new feature matcher based on the GLS strategy. Guided by the results of global searching stage, the local searching stage further improved the matching accuracy and reliability of the results. Our experimental results confirmed that GLS–MIFT achieved high-quality matching for a large-scale dataset of 1110 image pairs, with various multimodal image types from the fields of computer vision, medicine, and remote sensing. GLS–MIFT outperformed state-of-the-art methods including SIFT, RIFT, HOWP, OFM, MatchFormer, SemLA and GIFT in qualitative and quantitative evaluations. Our implementation and datasets are available at: https://github.com/Zhongli-Fan/GLS-MIFT.

Superior strength-ductility combination in TiC/TC4 composites via In situ construction Ti2Cu nanoparticles

Synergistic improvement of strength and ductility is challenging in the engineering applications of titanium matrix composites (TMCs). Herein, we fabricated the TC4 composites reinforced with grain boundary micron-TiC and intragranular nano-Ti2Cu using spark plasma sintering (SPS) and hot rolling (HR) to achieve a good balance between strength and ductility. An interfacial reaction between Ti and C forms the grain boundary TiC, and the vast majority of intragranular nano-Ti2Cu precipitates to accommodate the severe lattice distortion caused by the solid solution of Cu in β-Ti phase. Benefiting from Ti2Cu nanoprecipitates and their ability to effectively suppress dislocation motion, precipitation strengthening, and dislocation strengthening are the main factors, in addition to grain refinement strengthening due to deformation processing, that contribute to the realization of the superior yield strength (YS) of 1360 MPa and ultimate tensile strength (UTS) of 1504 MPa in composites than TC4 matrix (YS = 986 MPa, UTS = 1160 MPa). Meanwhile, the interfacial strain-delocalization effect of TiC/Ti2Cu with Ti matrix, the shear-lag effect of TiC, and the sustained strain-hardening effect provided by TiC/Ti2Cu empower the composites with an outstanding ductility (fracture elongation of 8.4 %). This study highlights the untapped potential for improving the mechanical properties of Ti matrix composites.

Ultrastrong and High Thermal Insulating Porous High-Entropy Ceramics up to 2000°C.

High mechanical load-carrying capability and thermal insulating performance are crucial to thermal-insulation materials under extreme conditions. However, these features are often difficult to achieve simultaneously in conventional porous ceramics. Here, for the first time, it is reported a multiscale structure design and fast fabrication of 9-cation porous high-entropy diboride ceramics via an ultrafast high-temperature synthesis technique that can lead to exceptional mechanical load-bearing capability and high thermal insulation performance. With the construction of multiscale structures involving ultrafine pores at the microscale, high-quality interfaces between building blocks at the nanoscale, and severe lattice distortion at the atomic scale, the materials with an ≈50% porosity exhibit an ultrahigh compressive strength of up to ≈337MPa at room temperature and a thermal conductivity as low as ≈0.76W m-1 K-1. More importantly, they demonstrate exceptional thermal stability, with merely ≈2.4% volume shrinkage after 2000°C annealing. They also show an ultrahigh compressive strength of ≈690MPa up to 2000°C, displaying a ductile compressive behavior. The excellent mechanical and thermal insulating properties offer an attractive material for reliable thermal insulation under extreme conditions.

Calculation of positron annihilation lifetime in diamond doped with B, Cr, Mo, Ti, W, Zr

Metal-matrix diamond composites have been extensively used and studied, but vacancies, doping, and other defects caused by the pretreatment of the diamond surface significantly affect the interface property between the metal base and diamond. Although techniques like transmission electron microscopy and spectroscopy analysis have been used to detect defects, they present certain limitations. Calculating the positron annihilation lifetime in diamond provides an accurate assessment of interface defect in the diamond. This study uses first-principles calculation methods and adopts various positron annihilation algorithms and enhancement factors, to compute the positron annihilation lifetimes in ideal diamond crystals, single vacancies, and diamond crystals doped with B, Cr, Mo, Ti, W, and Zr. The results, obtained by using local density functional in combination with Boronski &amp; Nieminen algorithms and random-phase approximation restriction as annihilation enhancement factors, indicate that the computed positron annihilation lifetime of diamond is 119.87 ps, which is consistent closely with the experimental result in the literature. Furthermore, after B, Cr, Mo, Ti, W, and Zr atoms are doped into diamond (doping atomic concentration of 1.6%), the positron annihilation lifetimes change from a single vacancy 119.87 ps to 148.57, 156.82, 119.05, 116.5, 117.62, and 115.74 ps respectively. This implies that the defects due to doped atoms in diamond change their positron annihilation lifetimes, with the influence varying according to the different atoms doped. Based on the calculated electron density in diamond vacancies and doped atom areas, it is discovered that doping atoms do not cause severe distortion in the diamond lattice. However, after B and Cr atoms are doped, the positron annihilation lifetime increases significantly. The primary reason is that the relatively low positron affinity of B and Cr atoms results in an extended positron residence time in the vacancy, thereby increasing the annihilation lifetime. Overall, vacancies and doped atom defects in diamond will cause its positron annihilation lifetime to change. The above conclusions provide crucial theoretical references for detecting and identifying interface defects caused by doping treatment on the diamond surface during the preparation of metal-matrix diamond composites.

Spatial Correction of Cadastral Maps Based on Satellite Imagery

It is well known that most of the cadastral maps and property plans in Iraq are preserved in paper form, with the majority dating back to the 1930s. These maps are widely used for various purposes, such as urban planning, sewage networks, and electricity networks. However, most of these maps suffer from some distortion and wear, with some being torn and taped due to the nature of the paper material and its handling, resulting in severe physical distortion. To address these issues, it is necessary to convert these maps into a digital format and perform corrective processing to mitigate the effects of past errors. Scanning alone is insufficient as it introduces many errors. Recently, fast and accurate computer software has become available that can process data from these maps and paper drawings, including addressing the wear they have undergone, and update them to meet the needs of local authorities developing and investing in these maps and implementing development projects. This process is also essential for establishing a digital foundation for the database. Geographic Information System (GIS) applications are widely used to enhance and assist decision-makers in making decisions that align with their purposes and application scenarios.

Influence of atmospheric turbulence on coherent detection performance of space coherent optical communication

Space coherent optical communication technology is considered to be an important way to overcome the bottleneck in current high-speed space communication. However, atmospheric turbulence seriously limits its realization. Based on the Huygens-Fresnel principle and the low-frequency compensation power spectrum inversion method, this work first investigates the random distribution characteristics of the amplitude and phase of a Gaussian beam after it has been transmitted through atmospheric turbulence. Then, using the coherent mixing efficiency and communication bit error rate model, the influence of atmospheric turbulence on the performance of spatial coherent optical communication systems is obtained. Finally, a laser heterodyne detection experimental system is built to quantitatively study the influence of atmospheric turbulence on the coherent detection performance of spatial coherent optical communication. The conclusions drawn from this study are as follows. 1) The spatial phase distortion caused by the weak turbulence channel is relatively small and will hardly affect the light intensity distribution characteristics of the Gaussian beam. In the case of weak turbulence, the influence of weak turbulence on the performance of coherent optical communication system is almost negligible. The communication bit error rate will decrease rapidly with the increase of the number of single bit data photons. The communication signal-to-noise ratio can be better than 10&lt;sup&gt;–5&lt;/sup&gt; when the number of single-bit photons is greater than 10. 2) Moderate turbulence will change the intensity distribution characteristics of the Gaussian beam, but will not cause a serious shift in the center of the spot. Under moderate turbulence conditions, the coherent mixing efficiency decreases rapidly as the turbulence intensity continues to increase, but the communication bit error rate still decreases rapidly with the increase of the number of single bit data photons. At this time, increasing the number of single-bit photons can suppress the negative influence of moderate intensity turbulence on the performance of coherent optical communication systems. 3) Strong turbulence will cause severe spatial phase distortion of the beam, destroy the consistency of the light intensity distribution, and cause a serious shift in the center of the spot. Under strong turbulence conditions, the coherent mixing efficiency of coherent optical communication systems approaches zero, and increasing the number of single bit data photons cannot significantly reduce the bit error rate, seriously affecting the quality of coherent optical communication. Atmospheric turbulence is an important limiting factor for developing space coherent optical communication. This study can provide useful references for evaluating the performance of space coherent optical communication systems.

GRiD: Guided Refinement for Detector-Free Multimodal Image Matching.

Multimodal image matching is essential in image stitching, image fusion, change detection, and land cover mapping. However, the severe nonlinear radiometric distortion (NRD) and geometric distortions in multimodal images severely limit the accuracy of multimodal image matching, posing significant challenges to existing methods. Additionally, detector-based methods are prone to feature point offset issues in regions with substantial modal differences, which also hinder the subsequent fine registration and fusion of images. To address these challenges, we propose a guided refinement for detector-free multimodal image matching (GRiD) method, which weakens feature point offset issues by establishing pixel-level correspondences and utilizes reference points to guide and correct matches affected by NRD and geometric distortions. Specifically, we first introduce a detector-free framework to alleviate the feature point offset problem by directly finding corresponding pixels between images. Subsequently, to tackle NRD and geometric distortion in multimodal images, we design a guided correction module that establishes robust reference points (RPs) to guide the search for corresponding pixels in regions with significant modality differences. Moreover, to enhance RPs reliability, we incorporate a phase congruency module during the RPs confirmation stage to concentrate RPs around image edge structures. Finally, we perform finer localization on highly correlated corresponding pixels to obtain the optimized matches. We conduct extensive experiments on four multimodal image datasets to validate the effectiveness of the proposed approach. Experimental results demonstrate that our method can achieve sufficient and robust matches across various modality images and effectively suppress the feature point offset problem.

Elinvar-Like Effect Induced by High Lattice Distortion in Zr 6 Ta 2 O 17 Ceramics

Super strength and toughness, excellent deformation resistance, and high-temperature service performance are the key factors to determine the practical application of new thermal barrier coatings (TBCs). The limited mobility of dislocations and the internal inherent defects in ceramics will inevitably lead to the decline of strength–plasticity and the reduction of service performance. Introducing preexisting twin boundaries and stacking faults (SFs) or preparing ceramic materials with high configuration entropy has demonstrated to be an effective strategy for enhancing the mechanical properties of ceramics. However, due to the positive thermal expansion coefficient of most ceramics and the remarkable increase of structural disorder at elevated temperature, the problem of elastic softening has become a bottleneck restricting the high-temperature service life of new TBCs. In this paper, the deformation behavior of high configuration entropy Zr 6 Ta 2 O 17 ceramics at 25 to 1,200 °C was in situ monitored via digital image correlation technique and three-point bending test platform in high-temperature environment. A remarkable Elinvar-like effect appears in the Zr 6 Ta 2 O 17 ceramic. More interestingly, mechanical deformation dominates the severe lattice distortion (deformation twins, SFs) and the disorder–order transition of chemical order at the atomic scale, while temperature can further enhance the degree of lattice distortion and ordering of Zr 6 Ta 2 O 17 ceramics. Furthermore, the atomic fluctuations at high temperature promotes the comprehensive improvement of mechanical properties in the Zr 6 Ta 2 O 17 ceramics.

An improved Lagrange-based numerical model for machining Ti-6Al-4V alloy concerning tool cutting edge microgeometry

Current Lagrange-based machining models usually involve a sacrificial layer (LAG-SL) to facilitate the chip formation. Otherwise, severe element distortion error arises especially when tool cutting edge microgeometry is considered. In view of this limitation, an improved Lagrange-based machining model is proposed that acquires no sacrificial layer (LAG-nSL) and can simulate completely the cutting, unloading and cooling process. Through comparisons with plenty of experimental measurements, the presented model is found not only applicable for machining using tool with various edge radii, but also yields better outcomes of chip morphologies, forces and residual stress distribution.

Suppressing Jahn-Teller distortion and locking lattice water with doped Fe(III) in birnessite toward fast and stable zinc-ion batteries.

Birnessite has been regarded as a promising cathode material for aqueous zinc-ion batteries (ZIBs), but severe Jahn-Teller distortion and abrupt lattice collapse at deep charged states lead to serious problems such as poor capacity retention and short cycle life, which severely impede its practical applications. We herein report the construction of an advanced layered Fe-doped Na0.55Mn2O4·xH2O (Fe-NMO·xH2O) cathode to promote zinc-ion storage performance and electrochemical stability. An outstanding capacity of 102 mA h g-1 at a high current density of 20 A g-1 and a long cycle life of 6000 cycles have been achieved, comparable to the state-of-the-art manganese oxide-based cathodes. Both experimental measurements and theoretical calculations reveal that Fe3+ substitution and lattice water cooperatively stabilize the interlayer structure, accelerate zinc-ion diffusion, and improve electronic conductivity. Notably, Fe doping is conducive to alleviating the Jahn-Teller effect and locking lattice water, which effectively prevents phase transformation and lattice collapse during the (de)intercalation process. This work sheds light on the synergistic interplay between dopants and structural water in zinc-ion storage and demonstrates instructive strategies to regulate layered structures for ZIBs.

Evidence of infection of cassava plants with the begomovirus passionfruit severe leaf distortion virus in Brazil

Evidence of infection of cassava plants with the begomovirus passionfruit severe leaf distortion virus in Brazil

A note on the design of frequency-invariant beamforming with uniform concentric circular microphone array

Compared to the frequency-invariant beamformer (FIB) with uniform circular microphone arrays, the FIB with uniform concentric circular microphone arrays (UCCAs) can mitigate the deep nulls problem in the white noise gain (WNG) and the directivity factor (DF). The WNG of the FIB-UCCAs can be improved by increasing the number of microphones. However, certain Jacobi-Anger expansion based methods for FIB-UCCAs utilize a linearly transformed version of the beamformer coefficients to optimize the WNG, which may result in severe beampattern distortion at high frequencies. In this paper, we present a beamformer design method that is based on the Jacobi-Anger expansion but optimizes the WNG directly. We analyze the effect of the truncation error of Jacobi-Anger expansion and demonstrate that the proposed method can effectively reduce the beampattern distortion. Computer simulations illustrate the performance advantages of the developed method in terms of the DF and WNG.

High Entropy Alloy Deposition from an Aqueous Bath

A new alloy design approach based on the concept of high entropy alloy (HEA) has attracted attention during the last few years. HEA is defined as an alloy composed of five or more principal elements with a concentration between 5 and 35 at% of each element. Depending on the combinations of the elements, HEA could show high resistance to corrosion, fatigue and fracture toughness besides unique electrical and magnetic responses. The outstanding characteristic of HEA is attributed to the high mixing entropies and the severe lattice distortion related to the addition of multiple components. Due to this unique combination of properties and the potential for designing a wide variety of new materials, interests have been directed toward high entropy alloy films and coatings for applications where corrosion and oxidation protection are strongly required. This study attempted to deposit five elements (Ni-Co–Cu–Mo-W) from an aqueous bath on a low-carbon steel substrate by the direct current. The goal was to combine the properties of Ni-Co-Cu with Ni-W and Ni-Mo coatings. In this case, a HEA coating can be produced, which might maintain corrosion and wear resistance even at high temperatures and be suitable for application in aggressive environments. To understand better the role of entropy on the coatings properties, three electroplating systems were designed, including electroplating of five elements (Ni-Co-Cu-Mo-W), which was compared with electroplating of four elements (Ni-Co-Cu-W) and (Ni-Co-Mo-W). In this case, systems with different configuration entropy can be produced, and by characterizing them, the relationship between the entropy and the properties of the coating might be cleared.Electrodeposition was carried out in Hull-cell to find the alloy deposition's proper working window. The role of different parameters such as pH, current density, and complex agent on the coating's composition was studied. The morphology and composition of the Hull-cell coatings were checked by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy along with X-ray fluorescence spectroscopy. Finally, the hardness and corrosion resistance of the coatings was studied by the nanoindentation technique and polarization in NaCl. This study developed a single aqueous bath for the electrodeposition of Ni-Co-Cu-Mo-W, Ni-Co-Cu-W and No-Co-Mo-W, and suitable deposition conditions were determined. It was shown that besides the metal concentration ratio, pH was the most influential parameter in the codeposition of elements with different deposition mechanisms. Ni and Co were the main inducing elements in the deposition of Mo and W than Cu. In addition, Ni, Co, Mo and W deposited uniformly, while Cu showed a different behavior. A competition between Mo and W deposition was seen, and Mo deposited more preferentially than W. The coatings showed weak passivity behavior and comparison between coating’s corrosion resistance was a challenge since their corrosion behavior does not only depend on coating composition but also on coatings compactness and integrity. By comparing the nano-hardness of the coatings, it was seen that the Ni-Co-Cu-W system with even the lowest configurational entropy has the highest hardness value. Keywords: Electrodeposition; High entropy alloy; Alloy deposition; hardness; Corrosion resistance

Nickel content-dependent microstructure and mechanical properties of TiZrNbHfNi high entropy alloy thin films

Alloying is known as an effective strategy to improve the mechanical properties of metallic materials. Here we show that the microstructure and mechanical behavior of a TiZrNbHf1.6 high entropy alloy film can be highly tuned by Ni addition. The newly designed TiZrNbHf1.6Nix (x = 0, 0.4, 1.2, 1.8, 2.5, 3.0, 4.6) alloy films are synthesized by co-sputtering Ti, Zr, Nb, Hf and Ni elemental targets. The microstructure and mechanical behavior of the alloy films are investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and nano/micro-indentations. The microstructural analysis indicates that the TiZrNbHf1.6 film has a single body-centered cubic with columnar-nanograined structure. As Ni content increases to 0.4 or above, the films show a complete amorphous structure. Our theoretical analysis shows that the transition from the crystalline to the amorphous structure can be attributed to the large atomic radius difference and the change of the thermodynamic parameters (e.g., mixing entropy and mixing enthalpy) due to the Ni addition. Compared to the TiZrNbHf1.6 film with a hardness of 4.8 GPa, a hardness increase of 8–35% is achieved in the Ni-doped alloy films (5.2–6.5 GPa) as measured by nanoindentation. The elevated hardness may be attributed to the severe lattice distortion and the amorphous structure induced by the Ni addition. Furthermore, microindentation reveals a diversity of deformation behavior in those films with different Ni content. A homogeneous deformation (slight plastic pileup) occurred in the films with Ni content of 1.2 and 4.6, which is close to the deformation behavior of the crystal TiZrNbHf1.6 film. While the film with a Ni content of 1.8 exhibits a catastrophic cracking deformation. Finally, multiple shear banding dominates the deformation of these films with Ni content of 0.4, 2.5 and 3.0. Our findings demonstrate that ultrastrong and highly deformable amorphous high entropy alloy thin films can be developed by appropriate element addition, making them promising materials for corrosion and wear-resistant coatings.

In-situ alloying of NiTiNb ternary shape memory alloys via laser powder bed fusion using pre-alloyed NiTi and elemental Nb powders: Microstructure, phase transformation behavior and functional properties

Laser powder bed fusion (L-PBF) provides not only the advantage to make geometrically complex structures, but also the potential for in-situ alloying. In this work, (NiTi)100–xNbx (x = 1, 3, 5, 9 at%) ternary shape memory alloys were in-situ synthesized through L-PBF using a mixture of pre-alloyed near-equiatomic NiTi and elemental Nb powders. Low-Nb (1, 3 at%) alloys exhibit coarse columnar grains and high cracking tendency, while high-Nb (5, 9 at%) alloys show fine microstructure and low cracking susceptibility. Increasing Nb content leads to a transition from planar to cellular/dendritic growth, as a result of the increased constitutional supercooling (ΔTCS) and thermal undercooling (ΔTt) ahead of the solidification front. The L-PBF fabricated (NiTi)91Nb9 alloy shows comparable transformation characteristics to the conventional Ni47Ti44Nb9 alloy, with martensite start temperature (Ms) of 190 K and thermal hysteresis up to ca. 170 K after 20% pre-deformation. Achieving low Ms temperature with near-equiatomic Ni/Ti composition (i.e., Ni/Ti=1.024) is attributed to severe lattice distortion caused by Nb solution in the supersaturated matrix and the depletion of Ti to form the Ti-rich β-Nb phase, which resulted from the intrinsic rapid solidification associated with L-PBF. The in-situ alloyed (NiTi)100–xNbx alloys exhibit good mechanical and functional properties (total fracture strain >7%, and shape recovery rates >85%). This work may provide insights into in-situ alloying of NiTi-based ternary SMAs through L-PBF.