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Microstructure evolution and coarsening behavior of precipitated O phase were systematically investigated in this study, and the corresponding microstructures were characterized by scanning electron microscopy and transmission electron microscopy. The results showed that the original microstructure was composed of lath O phase, α2phase and B2 matrix. The precipitated O phase presented different morphologies and sizes during heat treatment. With the increase of solution temperature and holding time, the O phase occurred coarsening, with a thickness ranging from 0.73 increased to 2.64 μm. But the volume fraction decreased from 57.65 to 18.40 %. During aging treatment, large amounts of fine secondary acicular O phase have precipitated from the matrix. As the aging temperature increases, the O phase underwent coarsening and the thickness increases from 0.70 to 1.40 μm. However, the aging temperature has little effect on the precipitation of acicular O phase, and the volume fraction decreases from 37.66 to 33.32 %. Research found that the small-sized O phase gradually dissolved in the matrix, while the large-sized O phase grew. This phenomenon can be explained by Ostwald ripening mechanism. The TEM analysis revealed that the O phase occurred separation, mainly due to the diffusion of solute atoms and the embedding of B2 matrix. Meanwhile, the O phase had been completed and segmented. The coarsening mechanism of the O phase was also explained by the boundary splitting mechanism and terminal migration mechanism.

Selective laser melting (SLM) is one of the most widely used metal additive manufacturing (AM) technologies and has great potential for forming complex structured parts. As GH3625 superalloy becomes more demanding for complex structured parts, making SLM offers a unique opportunity for manufacturing complex structured superalloys. However, there are relatively few studies on the microstructural evolution of GH3625 superalloys prepared by SLM, and the high tensile strength but the low elongation of superalloy parts prepared by SLM are difficult to meet practical applications. To this end, the effects of different volume energy densities (VEDs) on the microstructure and fracture characteristics of superalloys are investigated in this paper. In addition, a method combining response surface methodology (RSM) with non-dominated ranking genetic algorithm-III (NSGA-III) is proposed to generate optimal process parameters to maximize yield strength, ultimate tensile strength and elongation of superalloys. To demonstrate that the application of the NSGA-III algorithm is outstanding, the NSGA-Ⅱ algorithm is considered for application to this optimization problem and the hypervolume (HV) index is used to objectively evaluate the superiority of these algorithms. The best Pareto front obtained is also verified. The results show that the melt pool size is proportional to the VED in the studied range, and the deepest molten pool is about 74 μm when the VED is 147.62 J/mm3; the smallest cellular grain in the XOY direction is about 0.27 μm when the VED is 66.14 J/mm3. In the optimization of tensile properties, the yield strength, ultimate tensile strength and elongation models constructed by RSM are significant with R2of 0.991, 0.9621 and 0.9391, in that order. The evaluation index HV indicates that the Pareto front obtained by NSGA-III has a higher priority than the Pareto Front obtained by NSGA-II with HV Finally, the obtained Pareto front was experimentally verified and the maximum relative errors of yield strength, ultimate tensile strength and elongation were only 0.87%, 0.57% and 2.89%, in that order. The proposed optimization method has high acceptability and will have a wider application area.

The high temperature compression is performed by isothermal compression tests using Gleeble 3500 thermo-mechanical simulator at a constant strain rate for the hot-pressed Nb-22.5Cr-2.5Mo alloy. The deformation temperature ranges from 800 to 1200 °Cand the strain rate ranges from 0.001 to 0.1 s−1. The high temperature flow behavior and deformation mechanism of the alloy are investigated based on the compression test data and TEM observation of the deformed microstructure. The results show that the ductile–brittle transition temperature of the alloy is about 800 °C, and the flow stress is sensitive to the deformation temperature and strain rate, in which the plastic deformation ability increases obviously with the increase of deformation temperature and the decrease of strain rate. Besides, the hyperbolic sine Arrhenius model with stress exponent of 3.131 and apparent activation energy of 402 kJ/mol is established for the peak flow stress. The value of apparent activation energy is higher than that of Nb metal (246 kJ/mol), which implies the existence of Laves phase NbCr2makes the deformation of the alloy more difficult. Moreover, it is found that the deformation mechanisms in the Nbssmatrix are mainly DRV controlled by the glide and climb of the dislocations and DRX formed by bulging nucleation mechanism, while the deformation mechanisms in the Laves phase NbCr2particles are mainly twinning and synchroshear of the Shockley partial dislocation.

Owing to the unique properties of high strength Ti-3Al-2.5V tube, wall thinning is prone to happen in tube bending. To accomplish tube precision bending forming, the wall thinning needs to be precisely predicted and effectively controlled. A theoretical model considering circumferential deformation was presented to reveal the inherent relationship for wall thickness distribution versus tube geometrical parameters, and its reliability was validated by published experimental results. Using finite element (FE) simulation combined with orthogonal test, the effect rules and significances of process parameters on wall thinning in numerical control (NC) bending for high strength Ti-3Al-2.5V tube were investigated. The results show that the significant factors sort from the largest to the smallest for wall thinning in tube bending as the clearance of tube versus mandrel Cm, axial feed of mandrel e, friction of tube versus mandrel fm, clearance of tube versus bending die Cb, clearance of tube versus wiper die Cwand push assistant speed of pressure die vp; the wall thinning decreases for the larger Cmand vp, while increases for the larger Cb, Cw, fm, and e. Furthermore, the prediction model of maximum wall thinning ratio was established based on the significant process parameters by multiple linear regression method. Compared with the results of orthogonal test, the relative error of that is less than 6.5%, which can be employed for rapidly predicting the wall thinning in tube bending.

The S280 ultra-high strength stainless steel was subjected to isothermal constant strain rate compression experiments under the conditions of deformation temperature 1000–1150 °C and strain rate 0.001–10 s−1by Thermecmaster-Z thermal simulation testing machine. The flow behavior of S280 ultra-high strength stainless steel was analyzed; the dynamic recrystallization critical strain model, dynamic recrystallization volume fraction model, dynamic recrystallization grain size and average grain size model of the steel were established, and its dynamic recrystallization behavior was numerically simulated. The results show that the flow stress of S280 ultra-high strength stainless steel increases with the increase of strain rate and the decrease of deformation temperature. The distribution of dynamic recrystallization volume fraction and average grain size in each deformation region after thermal compression is not uniform, and the dynamic recrystallization volume fraction increases with the increase of deformation temperature and decrease of strain rate; the average grain size increases with the increase of deformation temperature and strain rate. The numerical simulation results are in good agreement with the experimental results, which can provide a theoretical basis for the microstructure control of the steel during thermal deformation.

The copper nanowire (Cu NW) network is considered a promising alternative to indium tin oxide as transparent conductors for advanced optoelectronic devices. However, the fast degradation of copper in ambient conditions largely overshadows its practical applications. Here we demonstrate a facile method for epitaxial growth of hexagonal boron nitride (h-BN) of a few atomic layers on interlaced Cu NWs by low-pressure chemical vapor deposition, which exhibit excellent thermal and chemical stability under high temperature (900 °C in vacuum), high humidity (95% RH), and strong base/oxidizer solution (NaOH/H2O2). Meanwhile, their optical and electrical performances remain similar to those of the original Cu NWs (e.g., high optical transmittance (∼93%) and high conductivity (60.9 Ω/□)). A smart privacy glass is successfully fabricated based on a Cu@h-BN NW network and liquid crytal, which could rapidly control the visibility from transparent to opaque (0.26 s) and, at the same time, strongly block the mid-infrared light for energy saving by screening radiative heat. This precise engineering of epitaxial Cu@h-BN core–shell nanostructure offers broad applications in high-performance electronic and optoelectronic devices.

•The hot deformation behavior of Ti-2.7Cu was analyzed.•The activation energy and Arrhenius constitutive equation at strain 0.4 were calculated.•3D power efficiency diagram and 3D instability diagram were constructed.•Processing map was constructed and optimum deformation parameters were acquired.•The main deformation mechanism in the optimum zone was dynamic recrystallization.

The combination of energy storage and microgrids is an important technical path to address the uncertainty of distributed wind and solar resources and reduce their impact on the safety and stability of large power grids. With the increasing penetration rate of distributed wind and solar power generation, how to optimize capacity configuration of hybrid energy storage capacity to improve system economy and reliability has become a research hotspot. This article establishes a multi microgrid interaction system with electric‑hydrogen hybrid energy storage. The microgrid system uses distributed wind and solar power as the power source. Then, considering the uncertainty of wind and solar power, a distributed robust model with the goal of system operation economy and reliability was established. This model is used to optimize the configuration of energy storage capacity for electric‑hydrogen hybrid energy storage multi microgrid system and compare the economic costs of the system under different energy storage plans. Finally, the article analyzes the impact of key factors such as hydrogen energy storage investment cost, hydrogen price, and system loss rate on energy storage capacity. The results indicate that reducing the investment cost of hydrogen energy storage is the key to reduce operating cost of multi microgrid hybrid energy storage system.

Acquiring AlN/GaN digital alloys with matching coherent lattices, atomically sharp interfaces, and negligible compositional fluctuations remains a challenge. In this work, the nature and formation mechanism of the constituent elements of AlN and GaN atomic layers growth was examined by first-principle calculations and experimental demonstration. On the basis of the calculated formation enthalpies, we developed a hierarchical growth method wherein AlN and GaN growth units are digitally stacked layer by layer through metal organic vapor-phase epitaxy, which involves the growth sequence instantaneously to control chemical potentials of the hierarchical growth units under different atmospheres. High-resolution X-ray diffraction and transmission electron microscopy confirmed that the hierarchical GaN and AlN growth units of digital-alloyed AlN/GaN structures had coherent lattices, abrupt interfaces, and integral monolayers at the atomic scale. The cathodoluminescence properties featured with single emission, combined with theoretical results, demonstrated the capability of electronic energies via the digital-alloyed AlN/GaN superlattices. These results provide a basis for the realization of other digital-alloyed nitride semiconductors.

The thermal stability of Nb–Cr–Mo alloy with the composition Nb-22.5Cr-2.5Mo (at.%), was studied by thermal exposure experiments in vacuum conditions at 1200 °C for 30 h, 50 h, and 100 h. The phase composition consists of Nb and C15 NbCr2, and the vast majority of alloying element Mo is found in the Nb matrix not in NbCr2particles. The grain size of Nb matrix exhibits a certain degree of growth during the thermal exposure process, while the grain size of NbCr2has no obvious change due to its high thermal stability. After thermal exposure at 1200 °C for 100 h, the alloy keeps its higher strength by the solid solution strengthening effect of Mo and the dispersion strengthening of NbCr2particles. At the same time, it has good plasticity due to dislocation slip in the Nb matrix and the emergence of stacking faults, twins and partial dislocations in NbCr2particles.

In order to achieve the precision bending deformation, the effects of process parameters on springback behaviors should be clarified preliminarily. Taking the 21-6-9 high-strength stainless steel tube of 15.88 mm × 0.84 mm (outer diameter × wall thickness) as the objective, the multi-parameter sensitivity analysis and three-dimensional finite element numerical simulation are conducted to address the effects of process parameters on the springback behaviors in 21-6-9 high-strength stainless steel tube numerical control bending. The results show that (1) springback increases with the increasing of the clearance between tube and mandrel Cm, the friction coefficient between tube and mandrel fm, the friction coefficient between tube and bending die fb, or with the decreasing of the mandrel extension length e, while the springback first increases and then remains unchanged with the increasing of the clearance between tube and bending die Cb. (2) The sensitivity of springback radius to process parameters is larger than that of springback angle. And the sensitivity of springback to process parameters from high to low are e, Cb, Cm, fband fm. (3) The variation rules of the cross section deformation after springback with different Cm, Cb, fm, fband eare similar to that before springback. But under same process parameters, the relative difference of the most measurement section is more than 20% and some even more than 70% before and after springback, and a platform deforming characteristics of the cross section deformation is shown after springback.

Piezoelectric nanogenerators (PENGs) harvest various types of mechanical energy and exhibit remarkable potential for powering portable devices and wearable electronic systems. The insulating layer in the device can enhance the output voltage, however, people are still curious on the extreme effect when the dielectric thickness reaches the limit of atomic monolayer. Here we demonstrate vertically aligned growth of zinc oxide (ZnO) nanorods array directly on polycrystalline copper paper through the pre-orientation with two-dimensional (2D) hexagonal boron nitride (h-BN) monolayer. The h-BN layer effectively releases the misfit strain in ZnO nanoarray and leads to highly aligned and ultralong nanorods over 75 µm through chemical vapor deposition method. A flexible and transparent PENG based on h-BN/ZnO nanoarray/h-BN sandwiched structure was designed and fabricated. Ultrathin thickness and high barrier of h-BN strongly suppresses the movement of free-carriers in PENG device and improves the output voltage. It is found that the capacitance of PENG increases exponentially inversely proportional to the dielectric layer thickness and reaches 0.01 mF with 2D h-BN monolayer. The multilayer h-BN based PENG can generate open-voltage of 5 V and short-current of ∼ 18 μA, and achieve a maximum output power density up to 169 mW/cm2. A prototype transparent PENG has been achieved for harvesting walking energy and exhibits the practical potential for self-powered wearable devices in the future.

Plane strain assumption and exponent hardening law are used to investigate the plastic deformation in tube bending. Some theoretical formulae including stress, curvature radius of neutral layer, angle of neutral layer deviation, bending moment, wall thickness variation and cross-section distortion, are developed to explain the phenomena in tube bending and their magnitudes are also determined. During unloading process, the springback angle is deduced using the virtual work principle, and springback radius is also given according to the length of the neutral layer which remains unchanged before and after springback. The theoretical formulae are validated by the experimental results or the validated simulation results in literature, which can be used to quickly predict the forming quality of tube numerical control (NC) bending.

The isothermal constant strain rate compression test of Ti-4.2Al-0.005B titanium alloy was carried out by Gleeble-3800 thermal simulator at temperature 850∼1050 °C, strain rate 0.001∼10s−1and maximum deformation degree 60%. According to the experimental data, the Arrhenius constitutive model was established, the flow stress curve was analyzed, and the processing map based on polarity reciprocity model was established, which was further optimized by Zener-Hollomon parameter processing map and activation energy map. The results show that the flow stress curves respectively show dynamic recovery characteristics and dynamic softening characteristics under different deformation conditions respectively. The softening behavior of the flow stress curves under high strain rate is caused by temperature effect, while the softening behavior at low strain rate is caused by dynamic recrystallization. According to the established Polar Reciprocity Model processing map, the stable region is (870–990 °C/0.01–0.12s−1). Then, the Zener-Hollomon parameter processing map and activation energy processing map were established. Finally, the optimal processing parameters of the alloy are (870–990 °C/0.04–0.12s−1). The main deformation mechanism is dynamic recrystallization. Meanwhile, the rationality of Zener-Hollomon parameter diagram and activation energy diagram is verified. In the actual production process, the choice of technological parameters is provided in order to obtain good microstructure and properties.

A new fluorene‐co‐carbazole‐based copolymer (PFCD), with a bulky peripheral dendritic carbazole pendant at the 9‐position, has been designed and synthesized through a Suzuki polycondensation reaction. The resulting copolymer exhibits desirable properties, such as excellent solubility, good thermal stability, and electrochemical properties. PFCD also shows efficient blue light‐emitting properties with excellent color purity and high photoluminescent quantum yield. The results of the photophysical properties indicate that the large side dendron with peripheral carbazole groups can not only efficiently suppress the π‐stacking of polymer chains but also raise the HOMO level of the resulting polymer material. Thus, PFCD is expected to be a promising pure blue light‐emitting material and further experiments on electroluminescent properties, film morphology, and aggregation behaviors are in progress.

Series polymers of butyl methacrylate with various contents of 3-(trimethoxysilyl)propyl methacrylate (MSMA) that introduces crosslinking networks among the macromolecules upon hydrolysis and self-condensation have been synthesized by free radical polymerization, and the influence of crosslinking density on the film properties has been examined. The polymer solutions were spin-cast over a layer of polystyrene brush to yield homogeneous polymer films. When the films of about 30 nm thick were exposed to moisture and then heated at 60°C for hydrolysis and self-condensation of MSMA groups, the initially flat surfaces became slightly coarser but without apparent dewetting. Further annealing at 140°C resulted in dewetting of the thin films, whose morphologies in thermodynamic equilibrium were related to the chemical compositions of the polymers. The polymers having higher contents of MSMA exhibited significantly reduced dewetting at the high temperature, due to the higher density of crosslinking networks that restricted the molecular mobility. In contrast to the thin films of about 30 nm thick, thicker films (about 100 nm) showed only a slight dewetting, even non-dewetting at the elevated temperature.

A series of well‐defined poly(ether ketone ketone) (PEKK)/sodium sulfonated poly(aryl ether ketone) (S‐PAEK) block copolymers of high molecular weights was prepared by direct nucleophilic polymerization of hydroquinone with sodium 5,5′‐carbonylbis(2‐fluorobenzene sulfonate) (1) and PEKK oligomer (2). Varying the ratio of 1 to 2 used in polymerization can be used to control the degree of polymer sulfonation, which correspondingly affects the polymer solubility in solvents. Increasing content of 1 in the copolymers, slightly decreases their thermal stability which is nevertheless thermally stable up to 400 °C. Two Tg values, or one broad Tg, were observed in the DSC measurements of the block copolymers, indicating the existence of phase separation, which was further proved by phase‐separated morphologies as shown in atomic force microscopy images.© 2001 Society of Chemical Industry

Poly(ether ketone ketone) (PEKK) composites were developed using mica as a filler. Sulfonated poly(ether ketone ketone) (S-PEKK), a possible interfacial modifier, was coated on the mica surface with ca. 50 nm thickness, as observed by contact atomic force microscope (AFM). The morphologies of these materials were examined by scanning electron microscopy (SEM). In comparison with PEKK, significantly improved mechanical properties were obtained for the composite materials. With increasing content of mica in the materials, tensile modulus of the materials increased and ultimate elongation decreased. The composites containing 30 wt.-% of mica exhibited a maximum tensile strength of about 200 MPa while pure PEKK showed a tensile strength of 102 MPa. The composites filled with mica treated by S-PEKK displayed somewhat higher values of tensile strength and ultimate elongation than those generated using pure mica. The glass transition behavior and thermal stability of PEKK were not affected by the composition of the materials. The amount of mica used in the composites showed some influence on the coefficient of friction and wearing rate of these materials.

Abstract: Composite electron-diffraction patterns (EDPs) for any specified fcc matrix orientation containing deformation twin and/or strain-induced hexagonal close-packed ε martensite (shortened as hcp phase or hcp platelet subsequently) related to the matrix by specific orientation relationships have been computed and plotted. These results helped us to select the favorable fcc matrix orientation for distinguishing between deformation twin and hcp phase and to index experimental EDPs obtained by using transmission electron microscopy (TEM). The identification of structure features in cold-drawn MP159 alloy with 48 pct reduction in cross-sectional area was performed by using TEM, combined with the results from the computer-simulated composite EDPs. Investigation results demonstrated that the closely spaced, intersecting network of fine platelets formed during cold drawing is deformation twins, and no reliable evidence has been found for the presence of hcp phase, which was generally believed to explain the high strength attained in cold-drawn MP159 alloy in some literature. It follows that the significant increase in the strength due to cold working in MP159 alloy results predominately from the formation of the intersecting network of thin deformation twin platelets, which act as “cells” or “subgrains” and provide strong barriers to the movement of dislocations over large distances. In addition, the relatively high dislocation density makes a certain contribution to strengthening.

Elastic modulus is one of the most crucial mechanical property parameters that affects the plastic forming quality of bent parts, especially for springback. Elastic modulus practically varies with plastic deformation, and its precise description is necessary to enhance simulation precision for tube bending and gain steady, high-precision bent components by actual bending. Using repeated loading-unloading tensile tests (RLUTTs), the variation of elastic modulus of high strength 21-6-9 stainless steel tube (21-6-9-HS tube) in terms of plastic strain has been obtained, which its decreases rapidly at the beginning, then decreases tardily and tends to be stable in the end with increasing the plastic strain. The variation can be expressed as a first order exponential decay function. By embedding the variation of elastic modulus with the plastic strain into ABAQUS software to simulate numerical control (NC) rotary draw bending of the 21-6-9-HS tube, the prediction precision for the springback angle, springback radius, maximum cross section distortion ratio and maximum wall thinning ratio can be improved by 11.98%, 7.62%, 35.53% and 11.55%, respectively.

Hexagonal boron nitride (h-BN) is the most well-known wide band gap two-dimensional (2D) material (> 6 eV). To achieve its applications in optoelectronic devices, the conductance of h-BN must be implemented to the extent that it can be fabricated into a p–n junction. Here, we demonstrate a method to improve the surface current of p-type h-BN monolayer by introducing additional nitrogen gas flow during growth. First-principles calculations were conducted to show that nitrogen atmosphere can promote the formation of boron vacancy, making a low barrier site for Mg doping incorporation. Magnesium-doped h-BN monolayer was achieved using a low pressure chemical vapor deposition method under N2 flux. The surface current has been enhanced by three times up to 16 μA under 4 V external voltage. This approach provides potential applications of controllable conductive h-BN film for two-dimensional optoelectronic devices.

In order to improve bent tube forming quality and limit, the reasonable mandrel parameters need to obtain during tube bending process. A three dimensional (3D) elasto-plastic finite element (FE) model of the whole process of TA18 high strength titanium alloy tube during numerical control rotary draw bending (RDB) was developed based on the FE software of ABAQUS, and its reliability was verified. Then, simulation and analysis of the mandrel role in tube numerical control RDB was carried out by using the model. The results show that the wall thinning increases and the cross section distortion decreases with increasing of mandrel extension length or mandrel diameter. The optimal range of the mandrel extension length and mandrel diameter is 0.5mm-1.5mm and 5.2372mm-5.3872mm, respectively.

In order to improve the forming quality and limit of tube numerical control (NC) bending, it is necessary to select reasonable mandrel types. A finite element (FE) model of the whole process of TA18 high strength tube in NC bending was established based on the platform of ABAQUS, and its reliability was validated. Then, using the model, the effects of no mandrel, cylindrical mandrel, hemispherical mandrel and ball-and-socket mandrel on the distribution of tangential stress/strain, wall thinning and cross section distortion were studied. The results show that the shape, size and location of the tangential stress/strain distribution have no obvious difference for the NC bending without mandrel and with three mandrel types. For the bending without mandrel, the wall thinning is the smallest, and the cross section distortion is the largest, which exceeds the requirement of aviation standard. Three types of mandrel have no significant effect on the wall thinning, while the hemispherical mandrel is the most conducive to control the cross section distortion.

The authors report on growth and characterization of semipolar (112¯2) GaN films improved by an in situ SiNxpretreatment of m‐sapphire substrate surface. Formation of SiNxand Ga‐rich surface at the initial growth stages is evidenced by X‐ray photoelectron spectroscopy. With the SiNxpretreatment, the GaN nucleated island density decreases due to the reduction of nucleation density by the SiNxmask. X‐ray diffraction and Raman analyses show reduction of threading defect density for the SiNxpretreated GaN films. Cathodoluminescence studies show enhanced D0X emission and suppressed defect‐related emissions. The improvements in crystalline quality and optical properties of semipolar GaN films with the SiNxpretreatment are attributed to the reduction in nucleated island density and coalescence boundaries, and enhancement of the +c island sidewall facet growth under Ga‐rich growth conditions. An in situ SiNxpretreatment of m‐sapphire substrate surfaceis employed to modify growth of semipolar (112¯2) GaN films. Crystalline qualities and optical properties of semipolar GaN epilayers are significantly improved by the in situ SiNxpretreatment.

Taking the 21-6-9 (0Cr21Ni6Mn9N) high strength stainless steel tube (HSSST) of 15.88 mm x 0.84mm (diameter D x wall thickness t) as the objective, a three dimensional (3D) elastic plastic finite element (FE) model of the whole process of the 21-6-9 HSSST in numerical control (NC) rotary draw bending was established based on ABAQUS explicit/implicit code, and its reliability was validated. Then, the effects of process parameters on springback of the 21-6-9 HSSST in NC rotary draw bending were studied using the FE simulation based on orthogonal test. The results show that the effects of process parameters on springback angle and radius form high to low are the clearance between tube and wiper die C w, mandrel extension length e, clearance between tube and mandrel C m, friction coefficient between tube and wiper die f w, clearance between tube and pressure die C p, friction coefficient between tube and bending die f b, friction coefficient between tube and pressure die f p, friction coefficient between tube and mandrel f m, clearance between tube and bending die C b, bending speed o, push assistant speed of pressure die V p and e, C w, C m, f b, f w, C b, f m, o, C p, f p, V p, respectively. Springback angle and radius decrease with the increase of C w, e or decrease of C m, f b, f w, f m, C b, while the C p, f b, V p and o have no obvious influence on springback.

To achieve the precise numerical control (NC) bending and improve the forming quality of high-strength TA18 titanium alloy tube (TA18-HS tube), the significance of process parameters on cross section distortion in the TA18-HS tube NC bending should be clarified. Taking the TA18-HS tube of 6.35 mm x 0. 4064mm (out diameter x wall thickness) as the objective, a three dimensional (3D) elastic plastic finite element (FE) model based on virtual orthogonal test was used to explore the effects of process parameters on cross section distortion behaviors in the TA18-HS tube NC bending. The results show that the clearance between tube and mandrel Cm, the clearance between tube and bending die Cb, the friction between tube and wiper die fw and the mandrel extension length e are significant factors for cross section distortion in the TA18-HS tube NC bending, and the significant factors on cross section distortion from high to low are the Cb, e, fw and Cm. The cross section distortion degree increases with the increase of the Cb, fw, Cm or with the decrease of the e.

Graphene possesses many outstanding properties, such as high strength and light weight, making it an ideal reinforcement for metal matrix composite (MMCs). Meanwhile, fabricating MMCs through laser-assisted additive manufacturing (LAAM) has attracted much attention in recent years due to the advantages of low waste, high precision, short production lead time, and high flexibility. In this study, graphene-reinforced aluminum alloy AlSi10 Mg is fabricated using selective laser melting (SLM), a typical LAAM technique. Composite powders are prepared using high-energy ball milling. Room temperature tensile tests are conducted to evaluate the mechanical properties. Scanning electron microscopy observations are conducted to investigate the microstructure and fracture surface of obtain composite. It is found that adding graphene nanoplatelets (GNPs) significantly increases porosity, which offsets the enhancement of tensile performance as a result of GNPs addition. Decoupling effort is then made to separate the potential beneficial effects from GNPs addition and the detrimental effect from porosity increase. For this purpose, the quantitative relationship between porosity and material strength is obtained. Taking into consideration the strength reduction caused by the increased porosity, the strengthening effect of GNPs turns out to be significant, which reaches 60.2 MPa.

In order to reveal the friction role in deformation behaviors of high-strength TA18 tubes in numerical control (NC) bending, a three dimensional (3D) elastic-plastic finite element (FE) model of high-strength TA18 tubes for whole process in NC bending was established based on ABAQUS code, and its reliability was validated by the experimental results in literature. Then, the bending deformation behaviors under different friction coefficients between tube and various dies were studied with respect to multiple defects such as wall thinning, wall thickening and cross section deformation. The results show that the wall thinning ratio and cross section deformation ratio increase with the increase of the friction coefficient between mandrel and tube f m or decrease of the friction coefficient between pressure die and tube f p, while the friction coefficient between bending die and tube f b has no obvious effect on these. The wall thickening ratio decreases with the increase of f b, f m or decrease of f p.

The aligned carbon nanotube–polyaniline composites with partially coaxial structures were prepared by electrochemical polymerization of aniline, which show efficient electrical conduction attributed to the polyaniline layer and large surface or interface area for potential application in chemical sensors.