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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]

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]

The cladding layer of Ti-6Al-4V alloy was treated by traditional forging and ultrasonic-assisted forging with the self-made forging device. The forged titanium alloy cladding layer was characterized by scanning electron microscopy, and the hardness distribution of the counterparts was examined by Rockwell hardness tester. The reasons for the difference of microstructure under two different forging methods were analyzed, and the influences of ultrasonic amplitude and forging force on the microstructure were discussed. The results showed that the ultrasonic vibration-assisted forging process was more advantageous to the plastic deformation of titanium alloy cladding layer than the traditional forging process and was beneficial to the evolution of the original Widmanstatten structure to the duplex microstructure. Meanwhile, the hardness of titanium alloy cladding layer was improved by about 10%. Furthermore, with the increase of ultrasonic amplitude and forging force, the microstructure of titanium alloy cladding layer gradually changed to equiaxed microstructure with better properties. [ABSTRACT FROM AUTHOR]

The corrosion performances of X100 steels in the oilfield produced water with different temperature (30°C, 40°C, 60°C) under the simulated working conditions were studied by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) test. Energy dispersive spectroscopy (EDS) was used to measure the element composition of the sample after corrosion. The phase and chemical compositions of the specimens were analyzed by X-ray diffraction (XRD) and Raman spectrometry. The electrochemical results showed that the corrosion resistance of the specimen exposed for 24 hours increased with the increase of the testing temperature, indicating the better protective effect due to the corrosion product film formed under high temperature despite the impact of turbulence. The corrosion products consist of Fe3O4, Fe2O3, α-FeOOH, and γ-FeOOH. The corrosion mechanism model of X100 steel was established and the corrosion behavior was analyzed under simulated working conditions. [ABSTRACT FROM AUTHOR]

Dynamic recrystallization to a large extent determines the microstructure of near-α titanium alloys during the thermo-mechanical processing in α + β two phases zone. And the initial microstructure has a dramatic effect on the recrystallization behavior. Therefore, this paper deals with the recrystallization behavior of a near-α TA15 titanium alloy sheet with substantial prior deformed substructures during the annealing and hot tension at 800 °C. Undeformed and deformed regions of tensile samples, viz., static recrystallization and dynamic recrystallization, were studied respectively through EBSD observation. It was found that, the unusual intragranular nucleation of discontinuous recrystallization was observed in the relatively coarse grains, which was formed by the enclosed low angle grain boundaries rearranged by the thermally activated recovery. And most of the recrystallized grains manifested as three types of special grain boundaries, namely [0001]30°, 11 2 ¯ 0 75 ° and 13 8 ¯ 5 ¯ 3 90 ° , which showed the cusps in grain boundary energy and can stabilize the recrystallized grain embryo. The substantial prior deformed substructures of the employed TA15 sheet, viz., low angle grain boundaries and dislocations, can facilitate the formation of subgrains and nucleation, which brought about a mixture of continuous and discontinuous recrystallization, regardless of dynamic or static. During the hot tension, the activation of dislocations would accelerate the annihilation and rearrangement of dislocations, thus, recrystallization can take place more frequently, which finally leads to an equiaxed microstructure. • Quasi-in-situ annealing treatment of the initial TA15 sheet was carried out. • A mixture of continuous and discontinuous recrystallization was observed during annealing and hot tension. • Effect of substantial prior deformed substructure on the recrystallization behavior was investigated. [ABSTRACT FROM AUTHOR]

Abstract Mo–MoSi 2 high temperature structural materials were obtained by hot-dip siliconizing method. The results show that the silicon melt and molybdenum substrate have good wettability, molten silicon reacts with molybdenum substrate to form a molybdenum silicide phase with a columnar structure, and a strong MoSi 2 crystallographic preferred orientation (CPO) on the (110) crystal face is characterized. While, the Mo–MoSi 2 high temperature structural materials consist mainly of silicon rich layer, MoSi 2 layer, interface layer and molybdenum substrate. The coating surfaces contain a high silicon concentration (55–65 wt%) than the MoSi 2 layer (30–35 wt%). Moreover, the thicknesses and the average grain sizes of siliconized coatings increase sharply with increasing siliconizing time. The coatings thicknesses are 20, 25, 30, and 50 µm, respectively. And the average grain sizes are 6.9, 9.3, 11.7, and 11.8 µm, respectively. [ABSTRACT FROM AUTHOR]

The isothermal oxidation behavior of a single crystal nickel-based superalloy was investigated at 980 °C through XRD, SEM/EDX and EPMA. The mass gain process exhibited two periods: an initial stage followed by a steady-state stage. Based on the experimental results, the rapid formation of alumina and NiO was responsible for the initial stage of mass gain, and the formation of complex spinels phases may dramatically effect on the steady stage. The microstructure of oxidation film, from the top surface down to the base material, was clarified as Ni-rich oxides, Ni-Cr oxides, Cr-Ta-Co oxides, Ni-Al oxides and finally a continuous Al2O3. In addition, AlN formed in the γ′-free zone. The effect of oxidation film evolution on the oxidation kinetics and mechanism were discussed. [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]

The microstructure evolution of 25Cr-35Ni-1Mo radiant tubes was investigated after approximately two years of service in a continuous annealing furnace. The inner and outer tube walls were exposed to N-containing combustion environment and protective atmosphere, respectively. The decarburization feature analysis indicated that carbon content decreased toward the tube surface. However, precipitates at the inner and outer walls were coarser, their content increased and the microhardness value also increased compared to that in the central area. X-ray diffraction illustrated that M(C,N) and M(C,N) were the dominant carbide at the inner and outer walls, and precipitates in the central area were mainly MCand M(C,N) phases. The results were assumed to be associated with the nitridation phenomenon that occurred in the N-containing environment at elevated temperatures. [ABSTRACT FROM AUTHOR]

Abstract: The structural properties, crystalline quality and surface morphology of CdTe thin films without and with a ZnTe buffer layer grown on (001)GaAs by molecular beam epitaxy (MBE) have been studied. CdTe thin film directly prepared on GaAs substrate displays (111) orientation with an island growth mode, whereas the CdTe epilayers with a ZnTe buffer are (001)-oriented single-crystalline film with a two-dimensional (2D) growth mode. The morphology and surface root-mean-square (RMS) roughness of CdTe epilayers are also dramatically improved by using a ZnTe buffer. Furthermore, it is suggested that the high-temperature (HT) ZnTe buffer grown at 360 °C is more efficient for enhancing CdTe structural quality than the low-temperature (LT) one at 320 °C. The CdTe epilayer on the HT-ZnTe buffer shows a narrower full-width at half-maximum (FWHM) of double-crystal X-ray rocking curve (DCXRC) for (004) reflection and a smaller RMS roughness. [Copyright &y& Elsevier]

Abstract: Effect of zinc addition on the shear property evolution between Sn-0.7Cu solder alloy and their joints reflowed at 250°C was investigated. The shear strength of Sn-0.7Cu/Cu joint was found to be higher than of Sn-0.7Cu solder alloy. Although a small addition of zinc element strengthened Sn-0.7Cu solder alloy, it decreased the shear strength of Sn- 0.7Cu solder joints. Based on the fractography analysis and interfacial microstructure observation, it is proposed that the deposition of Cu-Zn intermetallic toward the interface during reflowing is largely responsible for the shear property evolution between the Sn-0.7Cu solder alloy and their joints. [Copyright &y& Elsevier]

Abstract: Microstructure evolutions of Ti-27Nb-8Zr (mass fraction, %) biomedical alloy subjected to different aging treatments after solution treatment were studied by optical microscopy, scanning electron microscopy and X-ray diffraction, and the influence of various microstructures on the elastic modulus and tensile strength was discussed. The results indicate that the Ti-27Nb-8Zr alloy after solution treatment consists of β+α” phases and has relatively lower elastic modulus and tensile strength, while for the alloy after aging treatment, it contains β, α and ω phases and exhibits significantly higher elastic modulus and tensile strength. With increasing of the aging temperature, the microstructure became coarser and the elastic modulus and tensile strength became lower. It is recommended that a Ti-27Nb-8Zr alloy with comparatively lower elastic modulus (85.5 GPa) and optimal comprehensive properties can be obtained by adopting following process: solution treatment at 800 °C for 1 h and then quenched, aged at 500 °C for 12 h then air-cooled. [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]

Abstract: Composites produced in nature, such as mollusk shells, bones, etc., are renowned for their unique structures and excellent properties. In this paper the microstructure and mechanical properties of the shell of Conus betulina Linnaeus are investigated. The results indicate that the mechanical properties of the shell are anisotropic. After removal of the organic protein in the shell, the three-point bending strength significantly decreases, to about 1/20th or 1/30th of the original value. The organic matrix plays an important role in the hierarchical structure of the conch shells, as it promotes load transfer between adjacent aragonite layers. [Copyright &y& Elsevier]

A Z-parameter method based on the Larson–Miller relationship is proposed to assess the remaining life of a CrMoV steel. It is found that the non-linear master curve of stress σ vs Larson–Miller parameter P of the steel can be expressed as: P=26.68-2.49 log σ-0.01σ. A family of curves parallel to the master curve can be expressed as: P=Z-2.49 log σ-0.01σ, where the value of Z represents the deviation from the master curve which corresponds with the deterioration in rupture properties. The deterioration in rupture properties is connected with the degradation of microstructure, namely the spheroidization of carbides in the pearlitic steel. A relationship between the value of the Z-parameter and the level of spheroidization E can be expressed as: Z=27.32-0.54E. A normal distribution is supported for the value of the Z-parameter by both normal probability plotting paper and Shapiro–Wilk normality tests. [Copyright &y& Elsevier]

Sn–Ag–Cu–Bi solders, which have high quality and performance that can meet the requirement of electronic packaging, have been investigated in this paper. The research was focused on the influence of aging on the microstructural evolution and mechanical properties in Sn–3Ag–0.5Cu–xBi (x=0–3 wt.%) solders. The effect of Bi was discussed based on the experimental results. The experimental results indicated that the addition of Bi enhanced the tensile strength of the solders but decreased their elongation. After aging treatment, Sn–3Ag–0.5Cu solder showed significant change in strength and elongation which resulted from the obvious coarsening of Ag3Sn and Cu6Sn5 intermetallics. As for Bi-bearing solders, Bi precipitation in Sn matrix was only observed in Sn–3Ag–0.5Cu–3Bi solder after being aged at 120 °C for 100 h, while all the Bi-bearing solders exhibited relatively stable mechanical properties with aging time which can be attributed to the strengthening effect of Bi from solid solution strengthening to precipitating strengthening. [Copyright &y& Elsevier]

The current work investigated the influence of aging treatment on fatigue crack growth behavior of eutectic Sn–Pb alloy. After aging treatment, the eutectic grain structure changed to particle structure. This seriously influenced the time-dependent fatigue crack growth behavior, as well as the cyclic dependent behavior resistance in near-threshold regime at high frequency, while having slight influence on the crack propagation in Paris regime. [Copyright &y& Elsevier]

Abstract: The effect of high magnetic field on the microstructure of (Cu, Ni)6Sn5 intermetallic compound layer in Sn0.3Ni/Cu couples at 250 °C was examined. The applied magnetic field changed the morphology of outer (Cu, Ni)6Sn5 crystals on the Sn side from faceted shape to stick shape. The high magnetic field affected the crystal orientations of (Cu, Ni)6Sn5 and reduced the Ni content in the outer layer. The morphology evolution of (Cu, Ni)6Sn5 is attributed to the content of Ni solute decreased by magnetic field. The effects of high magnetic field on the liquid convection and phase diagram are considered to be responsible for the Ni content. [Copyright &y& Elsevier]

High borated steel sheets containing 0.25 wt% to 4.0 wt% boron including hypoeutectic (0.28 wt% B and 2.11 wt% B), eutectic (2.43 wt% B) and hypereutectic (4.01 wt% B) compositions were tried to be fabricated by a novel strip casting technology, and the effects of boron content on sub-rapid solidification behavior and subsequent microstructural evolution together with mechanical properties was studied. It was found that the morphology of borides depended greatly on the boron content. When increasing boron, the morphological change of borides was network-like → grainy → cluster-like → plate-like. Various orientation relationships between different morphological borides and γ-Fe in as-cast steels were also identified. After subsequent hot-rolling and solution-treating, ultra-fine (<10 μm) borides were obtained in hypoeutectic and eutectic steels. Benefiting from that, excellent mechanical properties was achieved, which was much better than that of steels prepared by traditional ingot casting. Particularly, when the boron content approached eutectic composition, of which the effect on the microstructure and mechanical properties was more sensitive. The steels containing 2.11 wt% and 2.43 wt% boron exhibited different morphological borides with a total elongation of 14.1% and 8.0%, respectively. Moreover, a thin hypereutectic borated steel sheet was also prepared, but the borides were very large and the total elongation was very low. The correlation between microstructure and strength was clarified based on the Hall-Petch behavior and intermetallic strengthening effect. Smaller γ-grains and higher volume fraction of borides were responsible for higher strength. The plastic behavior of steels was influenced by strain-hardening rate that was determined by the volume fraction of γ-Fe matrix. A better sustainable strain-hardening capability was beneficial to extend the stage of uniform deformation and enhance the ductility. In addition, the mechanical properties of steels were also decided by the fracture mechanism that was dominated by the size of borides. [ABSTRACT FROM AUTHOR]

A 3‐layered composite plate is innovatively fabricated via composite rolling of 1.6 wt% B stainless steel surrounded by two layers of boron‐free steels. The tensile properties of composite and non‐composite plates are comparatively tested and analyzed. Besides, the microstructure evolution of the investigated plates is characterized in detail. It is found that the composite specimens exhibit higher tensile elongation comparing with that of non‐composite specimens. Specifically, the engineering strain of the 1050 °C × 30 min solution‐treated specimens reaches to 12.5 ± 0.8% which is 2.5–3.0 times as high as that of non‐composite specimens. In addition, the as‐cast lamellar borides break into bar‐shaped structures in hot rolled plates, however, their morphology and distribution hardly change after solution treatment. Besides, the transition regions between the core and clad layers are formed and characterized by medium‐sized recrystallized grains and fine borides in the solution‐treated composite specimens. The enhancement mechanism of tensile elongation is mainly analyzed in term of the geometrical restriction of necking in the composite plate during tensile deformation. This paper provides a promising method to effectively enhance the tensile fracture elongation for these metallic materials with poor plasticity like high borated stainless steels. [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]

In order to further improve the hot gas bulging formability of laser-welded TA15 titanium alloy tube, studies about the effects of initial microstructures on the formability were carried out at 800 °C. Vacuum annealing procedures were performed to obtain different microstructures. The formability of these TA15 titanium alloy sheets with different microstructures was subsequently investigated by hot tensile tests and hot gas free bulging. A unified physically based material model considering dislocation density, work hardening, recrystallization, grain size and damage was built to analyze the deformation process. Results show that a good agreement was achieved between the unified material model and experiment results. The evolution of physical variables such as recrystallization fraction, and grain size can be predicted properly by the model. In the unified material model, the initial dislocation density would affect the dynamic recrystallization (DRX) rate. The DRX rate would increase with the increasing dislocation density. Therefore more DRX occurred at the early stage of deformation of initial material with higher dislocation density, while most of the DRX occurred at the middle-late stage of deformation of the annealed material with lower dislocation density. The initial material demonstrated the best formability due to the wide occurrence of DRX at the early stage of deformation, which increased the fraction of high angle grain boundaries, refined the microstructure, promoted the occurrence of grain boundary sliding and enhanced the formability of the material. However, most of the DRX occurred at middle-late stage of deformation of annealed material, which may increase the softening rate and lower the formability. Hence increasing the occurrence of DRX at the early stage of deformation by increasing the initial dislocation density in the material is an efficient approach to improve the gas bulging formability. [ABSTRACT FROM AUTHOR]

This study investigated the features of grain boundary regions in a Ni-based superalloy which underwent creep deformation. Large grain boundary zones were denuded in fine γʹ precipitates but contained coarsened microscale γʹ rods. The coarsening direction of these rods was along the <110> of the γ matrix and γʹ precipitates. The orientation of the grain boundary zone was the same as that of the adjacent grain behind the migrating boundary. This result indicated that the formation of these zones was accompanied by the migration of the grain boundary. Then, numerous slip features were observed through detailed local disorientation analysis. It is proposed that the driving force for the grain boundary migration was the local stress induced by the dislocation creep. The dissolution–reprecipitation of the precipitates at the boundary migration front resulted in the directional coarsening of the γʹ rods. [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]

Abstract: High temperature corrosion and microstructure deterioration phenomenon of KHR35H radiant tubes had been investigated after a service life of approximately 2years in annealing process. Analyses revealed that deterioration in mechanical properties of the radiant tube was caused primarily by significant growth of precipitates during high temperature service. Internal oxidation and simultaneously in situ carbides dissolution were responsible for the formation of large number of voids and microcracks at the inner wall of the tubes, which brought the reduction of effective thickness of the tube wall and may act as crack sources under either thermal shock or creep deformation. [Copyright &y& Elsevier]

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]

In an artificial island construction project based on the large-scale marine reclamation land, the soil settlement is a key to affect the late safe operation of the whole field. To analyze the factors of the soil settlement in a marine reclamation project, the SEM method in the soil micro-structural analysis method is used to test and study six soil samples such as the representative silt, mucky silty clay, silty clay and clay in the area. The structural characteristics that affect the soil settlement are obtained by observing the SEM charts at different depths. By combining numerical calculation method of Terzaghi’s one-dimensional and Biot’s two-dimensional consolidation theory, the one-dimensional and two-dimensional creep models are established and the numerical calculation results of two consolidation theories are compared in order to predict the maximum settlement of the soils 100 years after completion. The analysis results indicate that the micro-structural characteristics are the essential factor to affect the settlement in this area. Based on numerical analysis of one-dimensional and two-dimensional settlement, the settlement law and trend obtained by two numerical analysis method is similar. The analysis of this paper can provide reference and guidance to the project related to the marine reclamation land.

Long-term microstructural stability is a major concern for candidate materials used in advanced ultra-supercritical (A-USC) power plants. In the present work, precipitation behavior of a nickel based superalloy designed for A-USC boilers, with a base composition of Ni-25Cr-20Co, was investigated during long-term thermal exposure under different stresses at 1043 K. The results showed that the coarsening of γ′ precipitates in the grain interior had occurred during thermal exposure in the presence and absence of stress. The microstructure around grain boundary was altered remarkably under stress. The precipitate-free zones (PFZs) commonly existed near the grain boundary in the gauge sections of specimens after long-term creep. Coarsened and elongated particles in the PFZs were identified as γ′-Ni 3 (Ti, Al) precipitates by chemical composition analysis and diffraction pattern. Furthermore, the morphology and distribution of MC-type carbides have no significant changes observed due to their good stability, but discontinuous M 23 C 6 appeared under stress, due to formation of PFZs resulting in dissolution of the adjacent M 23 C 6 . Besides, the creep-rupture mechanism was discussed to explore a potential approach for improving creep properties. [ABSTRACT FROM AUTHOR]

MoS 2 three dimensional (3D) architectures with various subunits were synthesized using glycerol to mediate the growth of MoS 2 crystals though a CS 2 -assisted hydrothermal approach. It has been found that the thickness and lateral size of subunits can be distinctly reduced by increasing glycerol content in the mixture solvent. A stable porous MoS 2 architecture, composed of nanosheets with a tiny size, ∼3 layers and expanded interlayer distance, namely MoS 2 -15, was obtained when the volume proportion of glycerol reaches 15%. The sample MoS 2 -15 exhibits superior electrochemical performance in lithium ion storage, due to reasonable design as well as smart organization of MoS 2 subunits, featured by a capacity of 1027 mAh g −1 at 0.1 A g −1 after 100 cycles and 738 mAh g −1 at 5 A g −1 after 300 cycles, exceeding other MoS 2 nanostructured materials in this work. More importantly, the as-prepared various architectures exhibit tunable electrochemical behaviors depending on structure and morphology evolution, which truly reflects the potential to optimize the microstructure for lithium-ion host materials. [ABSTRACT FROM AUTHOR]

To analyze the microstructure across thickness exposed to various environment of the pyrolysis furnace tubes, the sample of Cr35Ni45Nb heat-resistant steel from a five-year service tube was sliced into slices from inner to outer wall. Moreover, microhardness was examined to investigate the influence of the microstructure on the property of the heat-resistant steel. The results show that the primary carbides Cr 7 C 3 and NbC have transformed into chromium-rich Cr 23 C 6 and niobium-rich carbides G phase in the middle section of the aged pyrolysis furnace tube. The Cr 2 O 3 and SiO 2 layer covered the outer and inner surfaces, and the Cr-depleted zones were formed under the oxide layer of the inner and outer walls. The carbides of M 23 C 6 were transformed into M 7 C 3 type carbides in the carburization zone under the Cr-depleted zone of inner surface, while the M 7 C 3 type carbides also existed under the Cr-depleted zone of outer wall. [ABSTRACT FROM AUTHOR]

In this article, the hot deformation mechanism of a laser-welded near α TA15 Ti-alloy joint was studied by hot tensile tests conducted at temperatures ranging from 800 °C to 900 °C with strain rates ranging from 1.0 × 10 − 1 s − 1 to 1.0 × 10 − 3 s − 1 . The results show that the main hot deformation mechanism of the laser-welded TA15 Ti-alloy joint is continuous globularization, but dynamic recrystallization (DRX) plays an important role during the globularization process. The morphology of α phase exerts considerable influence on the DRX mechanism. When the lamella microstructure is dominant in the weld seam, continuous dynamic recrystallization (CDRX) is the active mechanism; whereas with the increasing fraction of equiaxed grains in the weld seam, discontinuous dynamic recrystallization (DDRX) seems to be the dominant mechanism during the tensile deformation. The globularization process can be divided into three stages based on the characteristics of the microstructure. Under such a deformation mechanism, the laser-welded TA15 Ti-alloy joint tends to have a good formability at high temperature and small strain rate. A maximum elongation of 292% was achieved at 900 °C, 0.001 s − 1 , which exhibits superplastic characteristics. [ABSTRACT FROM AUTHOR]

In this work, a 0.71 wt%Si+0.44 wt%Al as-cast strip was produced by novel twin-roll casting. Some as-cast samples were respectively reheated and hot rolled at different temperatures in order to obtain different microstructure prior to cold rolling and annealing. The effects of the hot rolled microstructure on microstructure, texture evolution and magnetic properties were investigated in detail. A coarse deformed microstructure with λ-fiber texture was formed after hot rolling at 850–1050 °C, finally leading to an inhomogeneous recrystallization microstructure with strong λ-fiber, Goss and extremely weak γ-fiber texture. By contrast, a fine transformed microstructure was formed after hot rolling at 1150–1250 °C, finally leading to a fine and homogeneous recrystallization microstructure with stronger α-fiber, γ-fiber and much weaker λ-fiber texture. It should be noted that both the magnetic induction and core loss non-monotonically decreased or increased according to the hot rolling temperature. The unfavorable α-fiber and γ-fiber textures in the annealed sheets were much weaker than those of the conventional products regardless of the hot rolling temperature, thus contributing to a much higher magnetic induction. However, the average grain size in the annealed sheets was much lower than those of the conventional products regardless of the hot rolling temperature, thus leading to a higher core loss except the case of 1050 °C. Hence, it is underscored that better integrated magnetic properties than those of the conventional products can be obtained by optimizing the hot rolled microstructure to produce final desirable recrystallization microstructure and texture. [ABSTRACT FROM AUTHOR]

Abstract: In this study, 304 stainless steel coatings were deposited on interstitial-free steel substrate by cold spraying method. The effect of annealing treatment on microstructure, microhardness, ultimate tensile strength and fracture performance of the coatings were studied. The results showed that annealing treatment had made a dominant contribution to heal up the incomplete interfaces between the deposited particles. Both of the microstructure and the mechanical properties have been obviously optimized by annealing treatment. In addition, the coating microhardness decreased from 345 HV0.2 for the as-sprayed coating to 201 HV0.2 for the annealed coating. The coating ultimate tensile strength increased from 65MPa for the as-sprayed coating to 357MPa for the annealed coating, which resulted from the increase of the metallurgically bonded areas in the coating induced by annealing treatment. Fracture morphology of the coatings also revealed that annealing treatment changed the fracture character of the cold sprayed 304 stainless steel coating from brittle type to plastic type. [Copyright &y& Elsevier]

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]

• The paramagnetic structure of HPNb alloy change into ferromagnetic after carburization. • The M 23 C 6 carbides are replaced by carbon-rich M 7 C 3 carbides in carburization zone. • The carburized tube furnace tubes become brittle after carburization. • Carburization reduced the high temperature creep strength of HPNb alloy tube. The structure characteristics and mechanical properties of as-cast and carburized HPNb alloy tubes were investigated in this paper. Through magnetism test by the vibrating sample magnetometer, we find that the paramagnetic structure of as-cast HPNb alloy tubes has changed into ferromagnetic structure after carburization. Electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD) analyses show that the M 23 C 6 type carbide transformed into M 7 C 3 type carbide in carburization zone. Due to the coarser primary carbides and blocky-shaped secondary carbides after carburization, the ductility and toughness of the ethylene cracking furnace tubes are very low and become brittle. At high temperature, the tensile strength and yield strength of carburized tube are higher than those of as-cast tube, but the tensile elongation is lower. Owing to the microstructure degradation, the creep strength of HPNb alloy decreased after carburization. Hence, the carburization also could lead to the decrease of the remnant life of the pyrolysis furnace tubes. [ABSTRACT FROM AUTHOR]