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NiAl alloy sheet was successfully prepared using current-assisted sintering, thus verifying the possibility of preparing a NiAl thin-wall component by current-assisted sintering and foil/foil reaction synthesis. Ni/Al laminated sheets were obtained by annealing at 550 °C at 5 MPa for 0.5 h; uniform NiAl alloy sheets were fabricated by annealing at 1150 °C at 15 MPa for 20 min. The experimental results showed that current-assisted sintering significantly reduced the reaction temperature and reaction time. Microstructural characterization revealed that the inter-diffusion ability of Al atoms is considerably weaker than that of Ni atoms. Molecular dynamics simulation confirmed these experimental results and showed that this difference becomes significant under the action of an electric field. The mechanism of synthesis of Ni/Al laminated sheets using current sintering is mainly determined by the diffusion behavior of Ni atoms. [ABSTRACT FROM AUTHOR]

Herein, a novel method is proposed to prepare the multimaterial composite component for aerospace applications using the current sintering. Two representative high‐temperature structural materials, the new potential intermetallic NiAl and the widely used Ni‐based superalloy K4202, have been employed to achieve the target. As shown by the results, a clean interface with almost no defects is successfully obtained in NiAl/K4202 alloy. Nevertheless, the existence of a continuous Cr(Mo) phase along the region leads to an insufficient bonding ability. To optimize the interfacial microstructure, a Ni foil is employed as the interlayer. The results indicate that the interlayer can hinder the intense diffusion of elements and prevent the abnormal growth of Cr(Mo) phases, which result in a considerable improvement of interfacial properties. [ABSTRACT FROM AUTHOR]

By applying the TC4-Ti2AlC composite coatings to the Ti6Al4V substrate by laser, the wear resistance of the Ti6Al4V alloy was improved. Analysis was done on the composite coatings' microstructure, phase composition, microhardness, and tribological characteristics. According to the findings, coatings without defects can be created when Ti2AlC content ranges between 5 and 15 wt.%. Furthermore, the coating without Ti2AlC consisted of a α-Ti solid solution while coatings with Ti2AlC included a α-Ti solid solution, hard phases of TiC and Ti3Al, as well as a Ti2AlC ceramic phase. During laser cladding, Ti2AlC partially dissolved and turned into TiC and Ti3Al, resulting in an average hardness of 371.61 ± 3.95 HV0.5, 382.92 ± 3.61 HV0.5, 388.91 ± 3.29 HV0.5 for the coatings with Ti2AlC weight fractions of 5, 10, and 15%, respectively. These numbers were about 1.16 ~ 1.22 times the hardness of the titanium alloy matrix (320 ± 3.12 HV0.5). Besides, the Ti2AlC lubricant and hard phases act synergistically to bring composite coatings better performances in wear resistance and friction reduction compared to the pure TC4 coating. The lowest coefficient of friction (0.382) (COF) and the greatest wear resistance (8.87 × 10−5 mm3/N m) were obtained at the composition of TC4-10wt.%Ti2AlC; more particularly, the wear resistance at TC4-10wt.%Ti2AlC was 1.2–2.1 times that of pure TC4 coating. The principal causes of wear in a pure TC4 coating are adhesive wear and oxidation, however, these wear processes shift to minor abrasive wear and oxidation when assisted by oxide coatings, Ti2AlC lubricant, and TiC, Ti3Al hard phases. [ABSTRACT FROM AUTHOR]

High-borated stainless steels prepared via ingot casting and hot rolling have a relatively low ductility, which limits their use as structural and functional materials in fuel reprocessing systems. In this study, 2.1 wt.% B stainless steel composites were prepared by a novel method of hot-roll bonding and solution treatment using an ingot casting slab and two layers of boron-free stainless steel. The aim of this study was to determine the effect of solution treatment on the interfacial microstructure and mechanical properties of high-borated stainless steel composites. As expected, a high-borated stainless steel slab containing many brittle ceramic (Cr, Fe)2 B-type particles was successfully hot-rolled and bonded with boron-free stainless steel slabs. Furthermore, metallurgical bonding was realized via the formation of ~ 50 μm wide transition regions by solution treatment, for which the mechanism was found to consist of recrystallization and diffusion-controlled reactions. The formation of transition regions enhanced the geometrical restriction effect. Neither delamination nor cracking was observed along the interfaces during a bending test of the composite plates. [ABSTRACT FROM AUTHOR]

Turbine blades are the most demanding components in aircraft engines, and their performance is related to the safety of the whole engine. Due to the complex service environment and harsh service conditions of blades, various types of damage cannot be prevented in service. Therefore, it is of great engineering and economic significance to study the service damage of blades. In this paper, the directional solidification alloy turbine blade after actual service was selected as the research object. The cross section position of 80% upper height of the blade was intercepted, and the qualitative and quantitative microstructure analysis was carried out by SEM and EDS analysis. The results show that there are two different types of γ' phases in this leaf. One kind of γ' phase has small size and regular shape, the other has large size and irregular shape. The degree of microscopic damage among different parts of the blade is characterized with the help of dimensional distribution characterization of the γ' phase of each part, combined with the analysis of hardness testing of each part of the cross-section.The results show that the service conditions of different parts are different, and the degree of microstructure damage is different. In addition, matrix crack and coating crack in some parts of blade are summarized and analyzed. [ABSTRACT FROM AUTHOR]

Various constraints exist in bipedal movement. Due to the natural ability of effectively handling constraints, trajectory optimization has become one of the mainstream methods in biped gait planning, especially when constraints become much more complex on non-flat terrain. In this paper, we propose a multi-modal biped gait planner based on DIRCON, which can generate different gaits for multiple, non-flat terrains. Firstly, a virtual knot is designed to model the state transitions when the swing foot contacts terrain and is inserted as the first knot of the target trajectory of the current support phase. Thus, a complete gait or multi-modal gaits sequence can be generated at one time. Then, slacked complementary constraints, which can avoid undesired trajectories, are elaborated to describe the coupling relationships between terrain information and bipedal motion for trajectory optimization based gait planning. The concrete form of the gait planner is also delivered. Finally, we verify the performance of the planner, as well as the structural design of our newly designed biped robot in CoppeliaSim through flat terrain walking, stairs terrain walking and quincuncial piles walking. The three experiments show that the gaits planned by the proposed planner can enable the robot to walk stably over non-flat terrains, even through simple PD control. [ABSTRACT FROM AUTHOR]

The compromise between strength and plasticity has greatly limited the potential application of particles reinforced magnesium matrix composites (MMCs). In this work, the Ti particles reinforced AZ31 magnesium (Mg) matrix composites achieved simultaneous improvement in strength, elongation and wear resistance. The Ti particles reinforced AZ31 composites were fabricated by ultrasonic-assisted stir casting with hot extrusion. The results showed that a strong interfacial bonding was obtained at Ti/Mg interface because of the formation of semi-coherent orientation relationship of TiAl/Mg, TiAl/Al 2 Ti and Al 2 Ti/Mg interfaces. The as-extruded 6 wt.%Ti/AZ31 composite presented the best compressive mechanical properties and wear resistance with ultimate tensile strength, elongation and wear rate of 327 MPa, 20.4% and 9.026 × 10−3 mm3/m, obviously higher than those of AZ31 alloys. The enhanced mechanical properties were attributed to the grain refinement and strong interfacial bonding. The improved wear resistance was closely related to the increased hardness of composites and the formation of protective oxidation films. • Ti particles refine the grain size of Ti/AZ31 composites. • A strong interfacial bonding forms at Ti/Mg interface. • Ti/AZ31 composites get an increase in strength, elongation and wear resistance. [ABSTRACT FROM AUTHOR]

Objective: We investigated three-dimensional (3 D) reconstruction for the assessment of the tumor margin microstructure of hepatoblastoma (HB). Methods: Eleven surgical resections of childhood hepatoblastomas obtained between September 2018 and December 2019 were formalin-fixed, paraffin-embedded, serially sectioned at 4 μm, stained with hematoxylin and eosin (every 19th and 20th section stained with alpha-fetoprotein and glypican 3), and the digital images of all sections were acquired at 100× followed by image registration using the B-spline based method with modified residual complexity. Reconstruction was performed using 3 D Slicer software. Results: The reconstructed orthogonal 3 D images clearly presented the internal microstructure of the tumor margin. The rendered 3 D image could be rotated at any angle. Conclusions: Microstructure 3 D reconstruction is feasible for observing the pathological structure of the HB tumor margin. [ABSTRACT FROM AUTHOR]

• Silk fibroin@Ag spheres were prepared by in situ deposition of Ag nanoparticles on silk fibroin spheres. • Silk fibroin@Ag spheres were not cytotoxic and biocompatible. • Silk fibroin@Ag spheres showed antibacterial activity against the growth of bacteria. In this study, novel silk fibroin@Ag spheres were synthesized by in situ growth of Ag nanoparticles (NPs) on silk fibroin (SF) spheres and their microstructure, in vitro biocompatibility, and antibacterial property were evaluated. SEM observation showed that SF@Ag spheres had a spherical morphology with a diameter of 1–10 µm. TEM observation revealed that each SF@Ag sphere had a dense structure and its surface was deposited with Ag NPs with a diameter of 10–50 nm. In vitro biocompatibility evaluation indicated that SF@Ag spheres were not cytotoxic when incubated with osteoblast MC3T3-E1 cells. Moreover, when exposed to two representative types of gram-negative Escherichia coli and gram-positive Staphylococcus aureus , SF@Ag spheres showed a good antibacterial property against the growth of both types of bacteria. [ABSTRACT FROM AUTHOR]

• AgNWs@PVA composite films were fabricated via a unique combination method. • The AgNWs@PVA film shows high EMI SE of 55 dB at 11 μm ultra-low thickness. • The AgNWs@PVA film retains excellent stability after 2000 bending cycles. It remains still a challenge to prepare thin, flexible, conductive films for electromagnetic interference shielding, which are highly desired in next-generation electronic applications such as aerospace, medical and wearable devices, etc. Herein, silver nanowires@polyvinyl alcohol (AgNWs@PVA) composite films were fabricated via a unique combination of air plasma treatment followed by thermal sintering of AgNWs network. The prepared composite ultra-thin film (11 µm) with 24.2 wt% of AgNWs displays relatively low density of 1.58 g cm−3. Remarkably, the sheet resistance and electromagnetic interference shielding effectiveness are separately achieved to 0.29 Ω/sq and 55 dB at the measured frequency range of 8.2 GHz to 12.5 GHz. These traits underscore a significant promising prospect of AgNWs@PVA film in the modern flexible electronic devices. [ABSTRACT FROM AUTHOR]

High-efficiency and low-cost hot forming technologies for titanium alloys have been developed for producing complex-shaped, thin-walled tubular components under non-superplastic forming conditions. Under these forming conditions, there exist complex and highly integrated material evolution processes including microscopic heterogeneous deformation, microstructure evolution and damage behaviour. This paper presents an integrated crystal plasticity finite element model of near-α titanium alloys during non-superplastic hot deformation conditions considering grain boundary sliding (GBS), dynamic recrystallisation (DRX), as well as void evolution. The polycrystalline model of a near-α TA15 titanium alloy was established, containing α phase, β phase and grain boundary (GB) regions, in which the GB region was a visualised representation of GBS. The quantitative strength ratio between the GB regions and α phase was calculated according to the Zener–Holloman parameter Z and grain size, which determined the microscopic deformation behaviour. There were found to be two high microscopic strain regions in the α phase: intragranular deformation bands through the most favourable slipping and near the GBs through multiple slipping, which promoted continuous and discontinuous DRX, respectively. With the decrease in parameter Z or grain size, the activated dislocations accommodating GBS were found to no longer pile up inside the grain, but instead travel across the grain interior. Finally, methods to improve the macroscopic plastic formability were proposed for the difficult-to-form titanium alloys experiencing non-superplastic hot deformation. [ABSTRACT FROM AUTHOR]

ZrO 2 –Al 2 O 3 (ATZ) ceramics are attracting high interest in biomedical applications because of their desirable mechanical performance and biocompatibility. However, strength and toughness are mutually exclusive in structural ceramics. In this paper, based on digital light processing, novel textured ATZ ceramics with obvious crystallographic orientations were fabricated by incorporating Al 2 O 3 platelets with a high aspect ratio and equiaxed particles into the ZrO 2 matrix. The optimized fracture toughness of 16.9 ± 0.8 MPa m1/2 was achieved in the textured ATZ ceramic, which was about 67.3 % higher than non-textured ZrO 2 ceramics, without sacrificing strength. The coupling toughening effects of macrolayer structure, equiaxed and platelet-shaped Al 2 O 3 particles, and ZrO 2 particles were responsible for the enhanced mechanical performance. The macroscale toughening of 3D-printed lamellar architecture led to effective energy dissipation. Additionally, the crack deflection and crack branching induced by dual-morphology Al 2 O 3 particles, accompanied by the phase transformation of the ZrO 2 matrix, were significant microscopic toughening mechanisms. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiAlV sheet was prepared by magnetron-sputtering and foil-reaction process. • Solid-liquid reaction is applied without pressure to accelerate the process. • The tensile strength of NiAl-1.01V alloy was 128.9 % higher than pure NiAl at 1000 °C. To prepare NiAl sheets with improved high-temperature strength, the V layers with different thicknesses were deposited on the single-side of Ni foils by magnetron sputtering and then the hot-pressing of laminated Ni(V)/Al foils were carried out. A NiAlV sheet consisting of V precipitates and NiAl matrix was successfully prepared using this reaction technique of laminated foils. The NiAlV alloy prepared by microalloying method can obtain better mechanical properties (166.4 MPa) and retain considerable fracture strain (54.5 %) at high temperature. [ABSTRACT FROM AUTHOR]

To manufacture hard-to-deform intermetallics and their components at high temperatures and for a short-time, a novel additive sintering method based on solid-state powder densification is proposed, which aims to achieve the fabrication and joining of intermetallics. In this study, the sintering and joining of NiAl/NiAl and NiAl/TiAl alloys were conducted using this method. The results show that good bonding was achieved between similar intermetallics of NiAl/NiAl. Nevertheless, due to the formation of brittle phases, defects were observed in the bonding interface of the NiAl/TiAl alloy. An interlayer of V was employed to optimize the microstructure of the interface, which can prevent the formation of the brittle phase and improve the property of the interface. • A additive sintering method is proposed to manufacture dissimilar-material component. • The method can achieve fabrication and joining of dissimilar material simultaneously. • V foil as interlayer eliminates brittle IMCs at the joining interface of NiAl/TiAl. • The NiAl/V/TiAl sample shows significantly improved interfacial property. [ABSTRACT FROM AUTHOR]

The current-assisted forming process is considered to be a novel process that utilizes the electroplasticity effect to reduce the deformation resistance of difficult-to-deform metals and to refine the grain size while improving the mechanical properties of the part. However, the lack of understanding of the mechanisms by which pulsed current affects grain refinement still makes it difficult to experimentally develop analytical or empirical models of the relationship between grain size, pulse current parameters, and deformation amount. It will seriously hinder the further development and application of the current-assisted forming process. To reveal the mechanism of grain refinement coupling with electroplasticity, a series of Electron Back Scattering Diffraction observation tests were carried out after current-assisted plane strain compressions. The results show that the grain orientation spread value of the pulse current condition is lower than that of the non-current condition, while the refined grain area percentage is higher than that of the non-current condition. Based on the microstructure observation results, a cellular automata model for grain refinement is proposed. This consists of a dislocation density evolution, sub-grains generation, grain fragmentation, and a grain orientation rotation algorithm. To study the electroplasticity of the grain refinement process, the cellular automata model is also embedded with a finite difference numerical algorithm for solving the microscopic current density distribution of the model. The cellular automata model simulation results show that the error of grain size accuracy of this cellular automata model under non-current and pulse current conditions is 10.48% and 8.55%, respectively. It shows that the model can accurately characterize the grain refinement behavior of the current-assisted plane strain compression. The simulation results reveal the deep mechanism of pulsed current promotion on grain refinement, i.e., an inhomogeneous microstructure leads to uneven distribution of pulse current density. The inhomogeneous current distribution will further increase the grain refinement rate in the coarse-grained regions, thus increasing the proportion of the refined grain regions in the microstructure and leading to a relatively more homogeneous microstructure under pulse current conditions. The cellular automata model accurately reveals the mechanism of electroplasticity on the grain refinement. The model will serve as a crucial theoretical reference in designing current-assisted forming process routes to ensure excellent microstructure and properties in manufactured parts. It will enhance the widespread utilization of current-assisted forming process. [Display omitted] • The acceleration effect of pulse current on grain refinement was verified by the CAPSC tests. • There is a positive correlation between the intensity of the electroplastic effect and the degree of grain refinement. • An innovative cellular automaton model for grain refinement was constructed using the grain fragmentation theory. • The model introduces a pulsed current accelerated grain orientation rotation mechanism to couple the electroplasticity. • The inhomogeneous current density distribution will promote the production of a more homogeneous microstructure. [ABSTRACT FROM AUTHOR]

For fabricating NiAl thin-walled component and improving its high-temperature strength, a novel layered NiAlV composite sheet/cone consisting of NiAl(V) layer, NiAl–V hypereutectic layer and V (NiAl) layer have been successfully prepared using forming-reaction of laminated Ni/Al/V foils. Compared with pure NiAl, the ultimate tensile strength (UTS) of the NiAlV composite at 1000 °C is increased by 177%, which is mainly attributed to the solution strengthening and precipitation strengthening of V element. The obtained results provide a new approach for synergetic controlling shape and property of NiAl-based thin-walled component. • A forming-reaction method was proposed for fabricating closed cross-section thin-walled NiAl-based components. • Novel NiAlV composite sheet/cone consisting of different layer morphologies were successfully prepared. • The ultimate tensile strength of NiAlV composite was 201.6 MPa at 1000 °C (177% higher than pure NiAl). [ABSTRACT FROM AUTHOR]

The high-temperature anisotropy and microstructure evolution mechanisms of the rolled TA32 titanium alloy sheet were studied. The hot deformation behaviors of the TA32 sheet along the rolling direction (RD), diagonal direction (DD), and transverse direction (TD) were studied by the uniaxial tensile tests in the temperature range of 700–900 °C and the strain rate range of 0.0001–0.1 s-1. The anisotropic coefficients were calculated by interrupted tensile tests. The microstructure and texture characteristics were observed by electron backscatter diffraction (EBSD) characterization. The effects of dislocation slip, texture evolution, dynamic recrystallization (DRX), and grain morphology on high-temperature anisotropy were comprehensively studied. Results show that the TD sample exhibited the largest peak strength and the DD sample displayed the highest elongation. The r -values decreased with increasing temperature and decreasing strain rate, and increased with increasing strain. The dominant dislocation slip modes of RD, DD, and TD samples were prismatic slip, the coupling of basal and prismatic slips, and pyramidal slips, respectively. The DRX mechanism of TA32 titanium alloy during hot deformation was the combined effects of DDRX (discontinuous dynamic recrystallization) and CDRX (continuous dynamic recrystallization), and DDRX could weaken the anisotropy. The grain growth and refinement caused by thermal effect and DRX led to the decrease and increase of r -value, respectively. In addition, the room-temperature tensile strength of the TD deformed sample showed the largest drop compared with the initial sheet, which can be attributed to the accumulation of damage and the increase of basal texture in the TD sample during the hot working. [ABSTRACT FROM AUTHOR]