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

The coercivity of 2:17-type SmCo magnets is mainly determined by the gradient distribution of Cu element within the cell boundary phase, and the gradient of Cu distribution increases with aging time, together with coercivity. However, the fundamental origin of such Cu gradient distribution is not clear. In this work, the element redistribution and interfacial stress change during the aging process were simultaneously analyzed by employing typical Sm(Co bal Fe 0.16 Cu 0.08 Zr 0.03) 7.6 magnets with and without slow cooling. The increased atomic diffusion after slow cooling leads to a narrow width and large Cu distribution gradient of 1:5H phase, contributing to a high coercivity. Meanwhile, the lattice mismatch at the 1:5H/2:17R interface along 〈 1 ¯ 010〉 2:17R direction was enhanced in the magnet with slow cooling, giving rise to a large interfacial stress. Such interfacial stress was found, via physical chemistry analysis, to contribute to the gradient of Cu distribution in the 1:5H phase. The combined analysis of transmission electron microscopy, geometric phase analyses, and micromagnetic simulations reveal the presence of the interfacial stress together with a large concentration and gradient of Cu distribution in the 1:5H phase can improve the coercivity. These findings provide new considerations for the design of high-performance 2:17-type SmCo magnets. [Display omitted] [ABSTRACT FROM AUTHOR]

Tailings from gold mines gradually approach ultra-fine, making mine backfill costs higher and strength lower, which poses a serious threat to the safety of underground personnel and equipment. It is well known that suitable chemical admixtures can enhance the working properties of mortar materials. Therefore, in order to achieve the purpose of reducing the cost of ultra-fine tailings backfill and improving the working performance of ultra-fine tailings filling slurry, this paper provides a study on the effect of sodium silicate and calcium chloride on the properties of ultra-fine tailings cemented backfill materials. The results of experimental studies through rheology, strength, and microstructural tests, etc., showed that the optimal proportioning parameters of cementitious materials are 76.92% blast furnace slag, 19.24% carbide slag, and admixtures of 2.88% sodium silicate and 0.96% calcium chloride. The 3, 7, and 28-day uniaxial compressive strength of the ultra-fine tailings cemented paste backfill with the newly formulated blast furnace slag-based cementitious material increased by 124%, 142%, and 14%, respectively, compared to that of the ultra-fine tailings cemented paste backfill with the P. O42.5 cement. The setting time for ultra-fine tailings cemented backfill slurry is shortened by the addition of admixtures, and the shear stress of the slurry is correlated with the amount of hydration product generation and its formation of flocculating structure. Moreover, the cost of the newly prepared cementitious material is much lower than that of traditional cement, which lays a good foundation for the cemented filling of ultra-fine tailings. [ABSTRACT FROM AUTHOR]

Abstract In p-type γ -CuI thin films synthesized by the iodination of Cu layers with iodine vapor, a frosted-glass-like appearance with a rough surface is usually obtained, which makes it difficult to apply the γ -CuI films to transparent electronics. This paper proposes an innovative method for the preparation of highly transparent p-type γ -CuI films. A chemical reaction between Cu thin films and iodine vapor, combined with the layer-by-layer process at a temperature between room temperature and 120 °C are found to result in highly transparent polycrystalline γ -CuI films. The root-mean-square roughness values of the γ -CuI films prepared by this method are 8.5–21.2 nm, which are smaller than those for the γ - CuI films synthesized by the conventional method. The microstructure and optoelectronic properties of the γ-CuI thin films are sensitive to the temperature of iodine vapor. A high transmittance (80%) of the film obtained at an iodine vapor temperature of 80 °C has a low resistivity of 5 × 10−2 Ω cm and high mobility of 8.7 cm2/Vs. Moreover, a boosted figure of merit is realized due to the simultaneously low resistivity and high transparency: its value jumps from ∼488 to ∼1630 MΩ−1. Graphical abstract Unlabelled Image Highlights • A traditional iodination reaction method combined with the layer-by-layer process. • Simultaneously high transmittance and low resistivity. • A boosted figure of merit is realized. [ABSTRACT FROM AUTHOR]

In this work, Zn-1.5Cu-1.0Ag-xZr (x = 0, 0.1, 0.5, 1.0) alloys were used as raw materials to research the effects of Zr content and hot rolling on the microstructure and mechanical properties of the alloys. The results revealed that as-cast Zn-1.5Cu-1.0Ag alloy was composed of η-Zn phase and (Ag, Cu) Zn 4 phase. After Zr addition, Zn 22 Zr was precipitated in both as-cast and as-rolled Zn-1.5Cu-1.0Ag-xZr alloys, and a new phase of CuZn 5 was observed in as-rolled Zn-1.5Cu-1.0Ag-xZr alloys, resulting in the second phase strengthening. It was demonstrated that the grain sizes of the as-rolled alloys were much smaller than those of as-cast alloys, while Zr had slight effects on the grain sizes. In addition, Zn-1.5Cu-1.0Ag-0.1Zr alloy has the best as-cast and as-rolled mechanical properties, and the yield strength, ultimate tensile strength and elongation of above two alloys are 84.18 ± 0.71 MPa, 117.79 ± 0.52 MPa, 3.73 ± 0.40% and 218.14 ± 0.04 MPa, 244.83 ± 0.57 MPa, 64.50 ± 4.60%, respectively. Moreover, the strength and elongation of both as-cast and as-rolled Zn-1.5Cu-1.0Ag-xZr alloys increase initially and then decline with the increase of Zr content. • In this work, it can be proved that hot rolling can significantly reduce the grain sizes of as-cast alloys. • Among all the developed alloys, as-rolled Zn-1.5Cu-1.0Ag-0.1Zr alloy has the best comprehensive mechanical properties. • The strength and elongation of Zr modified alloys increase initially and then decline with growing of Zr content. 244.83 MPa [ABSTRACT FROM AUTHOR]

This paper presents an integrated multiscale model for the simulation of fibre reinforced polymeric composite laminate subjected to low velocity impact. The multiscale model is based on the embedded cell method, with detailed microstructure embedded into the macro laminate beneath the impact point, and a transition zone is introduced to link these two scales. Damage model is considered for the fibres and plastic behaviour for the matrix, and cohesive elements are used for the simulation of interface delamination. Both unidirectional and layup embedded cells are considered in the simulation so as to reveal the impact damage mechanisms from monolayer to layup levels. The simulation results indicate matrix cracking is the first damage form which occurs at the bottom of the laminate, and then delamination is induced when the matrix crack propagates to the interface, followed by fibre pull-out and fibre breakage. The simulation results are compared with available experimental results from literatures, with good agreements achieved between them on the damage morphologies. Thus the ability of the presented multiscale model to reveal the damage mechanisms of composite laminate under low velocity impact is validated. [ABSTRACT FROM AUTHOR]

The non-contact feature of the Laser/EMAT ultrasonic (LEU) technique is attractive for its NDT applications. However, it is challenging to apply it in thin structures because of the difficulties in the signal interpretations. In this work, the LEU technique is used to inspect the notch depths in thin steel plates. A Continuous Wavelet Transform (CWT)-based algorithm is developed to calculate the transmission coefficients of laser-generated Lamb waves. The effect of varying notch depths on Lamb waves’ transmission coefficients is investigated both numerically and experimentally. The transmission coefficients of laser-generated Lamb waves calculated using CWT have been used successfully to predict the notch depths in thin structures. [ABSTRACT FROM AUTHOR]

Gas hydrates can be free floating in the sediment matrix; contacting, but do not cement; actually cementing and stiffening the sediment. The microstructure and growth of gas hydrates (CH 4 and CO 2 ) in porous media were observed in situ by Magnetic resonance imaging (MRI). The experimental results confirmed the random nucleation of gas hydrates in porous media. The results show that hydrates are preferentially formed in the pore spaces. Hydrates then occupy the pores of porous media gradually, but do not cement the adjacent glass beads in the final stage. Gas hydrates are believed growing as free-floating model in porous media. [ABSTRACT FROM AUTHOR]

Abstract: Ni–Cu–P alloy film of 4.0wt%Cu and 10.1wt%P was deposited on Cu substrate through pulse electroplating. Microstructures, morphologies and phases of the alloy films were studied. Phase transformation kinetics of the alloy films during the DSC annealing was also investigated. The results show that the as-deposited Ni–Cu–P alloy film is composed of an amorphous Ni(Cu,P) matrix in which 5nm spherical Ni(Cu) grains are embedded. After the alloy film annealed at 673K, Ni5P2 precipitates from the amorphous matrix; and at 773K, Ni5P2 transforms into Ni3P, which is spherical and about 10nm in diameter. Meanwhile, the nanocrystalline Ni(Cu) grains grow up to be regular hexagon and 60–70nm in diameter. The activation energies related to the precipitation of Ni5P2 from the Ni(Cu,P) matrix and the phase transformation of Ni3P from Ni5P2 were deduced to be 178.3 and 238.4kJmol−1, respectively. [Copyright &y& Elsevier]

• The composite cement-sodium silicate grout mixed with SC and SLP are prepared. • Properties of composite grout in the still and flowing water are examined. • Scouring effect of flowing water causes negative effects on the grout concretion. • Appropriate dosages of SC and SLP improve the anti-scour ability of grout concretion. The properties of grouting materials within the flowing-water environment impact greatly the long-term effect of water-plugging engineering. In order to improve the performance of traditional cement-sodium silicate grouting material, the composite cement-sodium silicate grout mixed with sulphoaluminate cement and slag powder was prepared, and the properties of the composite grout and its concretion within the still and flowing water environments are investigated experimentally. The test results indicate that the scouring effect of flowing water causes negative effects on the strength and anti-permeability of grout concretion. Oppositely, the substitution of two admixtures with proper ratios improves obviously the comprehensive performances of composite grout to resist the effect of flowing water. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a new method to generate the random distribution of fibres in the transversal cross-section of fibre reinforced composites with high fibre volume fraction. The algorithm, named random sequential expansion (RSE) algorithm by the authors, is based on the hard-core model, but overcomes the jamming limit of hard-core model and is able to generate random distributions for high values of fibre volume fractions. By adjusting the inter-fibre distance parameters, it can generate microstructures with different fibre volume fractions expediently. Statistical analysis is performed on the generated distributions and a good agreement with the completely spatial random (CSR) pattern is found in all statistics analysed. Finite element analysis (FEA) is conducted to predict the effective properties of the generated microstructures. The predicted properties show reasonable agreement with the experimental results. The present algorithm is simple, highly efficient and provides a useful alternative to generate random numerical models that can be used in micromechanical analysis of composites. [Copyright &y& Elsevier]

Abstract: The effect of thermal residual stress on transverse failure of fiber-reinforced polymer matrix composites is investigated by computational micromechanics with finite element method (FEM). Especially, the effect of inter-fiber spacing on thermal residual stress and then its effect on the transverse failure of composites are studied through microstructures with random fiber distribution and controllable minimal inter-fiber spacing. The residual stress is supposed to be introduced by thermal contraction of both resin and fiber as a result of cooling from the curing temperature to room temperature. The calculated residual stresses generally increase with the increase of fiber volume fraction and decrease of minimal inter-fiber spacing. And initial matrix and interface damage may be induced by thermal residual stress, especially when the inter-fiber spacing is quite small. For the particular composite system studied and the assumed parameters, it is concluded that the existence of residual stress can have significant effects on the failure behavior of composite when subsequent external load is applied, obviously changing the damage initiation locus and damage evolution path, and causing significant decrease in the transverse strength of the composite. Generally, there is a trend of more significant decrease in the transverse strength for higher fiber volume fraction and smaller inter-fiber spacing. In conclusion, this paper reveals how inter-fiber spacing and thermal residual stress affect the transverse failure behavior of composites, and thus can provide some guidance for both design and analysis of composites when thermal residual stress is concerned. [Copyright &y& Elsevier]

This paper proposes a surface-tension-driven self-assembly method for manufacturing highly 3-D microstructures in microelectromechanical systems (MEMS). By using laser reflow soldering, various MEMS microstructures, even including the thermal-sensitive components, are able to be effectively assembled. Moreover, an energy-based numerical model is established for predicting the equilibrium geometry of a self-assembled structure. Based on the calculated results of energy and torque, an analysis is carried out on the factors affecting the self-assembled equilibrium position. In addition, the self-assembly process is also investigated experimentally by fabricating a popped-up microstructure with two light-emitting diodes die. Experimental studies, combined with the modeling results, have demonstrated that the self-assembly angle can be controlled within \pm2.5^\circ. Furthermore, in order to enhance the precision of self-assembly, a novel low-cost wire limiter structure fabricated by the wire bonding process is presented, which reduces the assembly angle variation down to \pm0.5^\circ. [ABSTRACT FROM PUBLISHER]

Abstract: The mechanical behavior of unidirectional fiber-reinforced polymer composites subjected to tension and compression perpendicular to the fibers is studied using computational micromechanics. The representative volume element of the composite microstructure with random fiber distribution is generated, and the two dominant damage mechanisms experimentally observed – matrix plastic deformation and interfacial debonding – are included in the simulation by the extended Drucker–Prager model and cohesive zone model respectively. Progressive failure procedure for both the matrix and interface is incorporated in the simulation, and ductile criterion is used to predict the damage initiation of the matrix taking into account its sensitivity to triaxial stress state. The simulation results clearly reveal the damage process of the composites and the interactions of different damage mechanisms. It can be concluded that the tension fracture initiates as interfacial debonding and evolves as a result of interactions between interfacial debonding and matrix plastic deformation, while the compression failure is dominated by matrix plastic damage. And then the effects of interfacial properties on the damage behavior of the composites are assessed. It is found that the interfacial stiffness and fracture energy have relatively smaller influence on the mechanical behavior of composites, while the influence of interfacial strength is significant. [Copyright &y& Elsevier]

Abstract: Microstructure, mechanical properties and bio-corrosion properties of as-cast Mg–Zn–Mn–Ca alloys were investigated for biomedical application in detail by optical microscopy, scanning electronic microscopy (SEM), mechanical properties testing and electrochemical measurement. SEM and optical microscopy observation indicated that the grain size of the as-cast alloys significantly decreased with the increasing of Ca content up to 0.5wt.%. Further increasing of Ca content did not refine the grain more. The phase constitute was mainly controlled by the atomic ratio of Zn to Ca. When the ratio was more than 1.0–1.2, the alloy was mainly composed of primary Mg and lamellar eutectic (α-Mg+Ca2Mg6Zn3), while the alloy was composed of primary Mg and divorced eutectic (α-Mg+Mg2Ca+Ca2Mg6Zn3) when the atomic ratio was less than 1.0–1.2. The yield strength of the as-cast alloy increased but the elongation and the tensile strength increased first and then decreased with the increasing of Ca content. It was thought that Mg2Ca phase deteriorated the tensile strength and ductility. Electrochemical measurements indicated that Mg2Ca phase improved the corrosion resistance of the as-cast alloy. [Copyright &y& Elsevier]

Abstract: Cauliflower-like TiO2 rough spheres, which are about 200nm large, have greatly enhanced light harvesting efficiency and energy conversion efficiency of dye-sensitized solar cells (DSC), due to their high light scattering effect and large BET surface area (80.7m2 g−1) even after calcinations at 450°C for 30min. The large size TiO2 rough and smooth spheres, produced at different initial temperatures by hydrolysis of Ti(OBu)4 with P105 (EO37PO56EO37) or F68 (EO78PO30EO78) tri-block copolymer as structural agents, have nearly the same diameter of ∼275nm and strong light scattering effects in the wavelength of 400–750nm. However, rough spheres have even higher light scattering effect and larger BET surface area than smooth spheres for the roughness of the surface. By adding 25wt.% large TiO2 spheres into the over-layer of TiO2 film composed of ∼20nm TiO2 particles as light scattering centers, the energy conversion efficiency of the film containing rough spheres reaches 7.36%, much larger than that of smooth spheres (6.25%). From another point of view, the TiO2 rough spheres may have the satisfying ability in other fields of application such as photo-catalysis, drug carriers and so on. [Copyright &y& Elsevier]

Compared with the fundamental mode in the optical fibers, the higher-order modes with unique dispersion characteristics give the radiation generated by nonlinearity a wider bandwidth. On this basis, a design scheme of single-mode operation in a few-mode optical fiber is proposed. All the core modes except the LP02 mode will be filtered out by introducing two microstructure cladding regions that are strongly coupled to the core modes with different refractive indexes. The simulation results show that the loss of the LP02 mode is less than 0.1 dB/m in the bandwidth greater than 20 nm, while the losses of other modes are greater than 10 dB/m, indicating that the fiber achieves effective transmission of a single high-order mode. This work broadens the concept of selective mode filtering design and may attract more researchers' attention to single high-order mode fiber applications. [ABSTRACT FROM AUTHOR]

• An antibacterial low elastic modulus alloy (Ti-13Nb-13Zr-10Ag) was prepared. • The α" martensite influenced local Ag content to promote Ti 2 Ag precipitation. • The β phase stabilization of Ag can reduce the elastic modulus of near-β alloys. • Ag can improve the corrosion resistance of near-β Ti alloys. Titanium alloys with good antibacterial properties and low elastic modulus have great potentials for biomedical application. Ti-13Nb-13Zr-xAg(x = 7,10) alloys were prepared to reveal the influence of Ag content on the microstructure, corrosion resistance, elastic modulus and antibacterial property. The results have shown that the decrease in the Ag content promoted the precipitation of Ti 2 Ag phase, thereby improving the antibacterial properties and reducing the elastic modulus of the material. Ti-13Nb-13Zr-10Ag achieved the high corrosion resistance, good antibacterial properties and low elastic modulus. [ABSTRACT FROM AUTHOR]

• The 3D microstructure of laser remelted Be-Al alloy was reconstructed by using FIB/SEM. • A significantly refined structure of the Be-Al alloy can be obtained through laser remelting. • The microstructure can be customized by optimizing the processing parameters. In this study, the beryllium-aluminum (Be-Al) alloy was processed using laser remelting (LR), and the microstructure was investigated using a 3D reconstruction technique. Focused ion beam/scanning electron microscope (FIB/SEM) reconstruction reveals that the microstructure consisted of a continuous network of Al phases wrapping the columnar Be phase. The columnar Be phases grow from the substrate towards the remelting zone and are oriented in different directions at the top of the molten pool. The gradient solidification rate explains well the gradual size reduction of the Be phase from the bottom to the top of the molten pool. These results reveal that LR is an effective method and that microstructures can be customized by optimizing the processing parameters. [ABSTRACT FROM AUTHOR]

Abstract Ti-6Al-2Zr-1Mo-1V (TA15) with ultrafine crystallites and numerous nano-scale twins were successfully prepared by selective laser melting (SLM). The room-temperature and high-temperature (500 °C) tensile properties of SLM-fabricated samples were visibly higher than those of TA15 fabricated by conventional techniques, other near α titanium alloys and even comparable to TA15-based composites. [ABSTRACT FROM AUTHOR]

The effect of heat treatment on the microstructure and properties of Mg-4Al-0.25Si-0.3Ca alloy was systematically studied. The results showed that after solution treatment at 420 ℃ for 10 h and 500 ℃ for 3 h, then aging at 220 ℃ for 7.5 h, the shape of Mg 2 Si and CaMgSi phases changed from continuous to discontinuous, while the Mg 17 Al 12 phased precipitated in the way of continuous precipitation in grains and discontinuous precipitation at grain boundaries during aging. The UTS of the alloy increased from 174.3 ± 4.0 MPa to 194.0 ± 5.0 MPa, and the corrosion current density decreased by 54%, The corrosion resistance was also improved, but the elongation decreased from 10.38 ± 0.37% to 9.1 ± 0.46%. • The Mg2Si phase and CaMgSi phase changed from continuous to discontinuous after 420 ℃ × 10 h, 500 ℃ × 3 h and 220 ℃ × 7.5 h. • After heat treatment, the UTS increased from 174.4 MPa to 194.0 MPa, the Icorr decreased, but the elongation decreased slightly. • The Mg17Al12 phase precipitated in two methods: intragranular continuous and grain boundary discontinuous precipitation. [ABSTRACT FROM AUTHOR]

Abstract: A simple phase-inversion process is successfully combined with a dip-coating process to fabricate anode-supported micro-tubular solid oxide fuel cells (SOFCs). Several processing parameters were systematically investigated to optimize cell microstructure and performance, including the amount of pore former used in the support substrate and the number of electrolyte coatings. Single cells with ∼240 μm thick NiO-YSZ support and 10 μm thick YSZ electrolyte were successfully fabricated, demonstrating peak power densities of 752 and 277 mW cm−2 at 800 and 600 °C, respectively, when a composite cathode consisting of La0.85Sr0.15MnO3 and Sm0.2Ce0.8O2−δ was used. This simple fabrication technique can be readily used for optimization of fuel cell microstructures and for cost-effective fabrication of high-performance SOFCs, potentially reducing the cost of SOFC technologies. [Copyright &y& Elsevier]

Abstract: Microstructure and mechanical properties of Mg–0.6Si–xZn alloys (x =0–1.6wt%) were investigated to reveal the modification effect of Zn on the morphology of eutectic Mg2Si. It was found 0.5–1.3wt% Zn effectively modified the morphology of eutectic Mg2Si from laminated structure to fine fiber, and in turn improved significantly the mechanical properties of Mg–Si alloy. Further increase in Zn content changed Mg2Si from fine fiber to Chinese script shape. It was suggested that the Zn content should not exceed 1.5wt% in Mg–Si–Zn alloy in order to get good mechanical properties. [Copyright &y& Elsevier]

The mechanical properties of an austenite-based Fe-Mn-Al-C lightweight steel were improved by co-precipitation of nanoscale Cu-rich and κ-carbide particles. The Fe-28Mn-9Al-0.8C-(0,3)Cu (wt.%) strips were near-rapidly solidified and annealed in the temperature range from 500 °C to 700 °C. The microstructure evolution and mechanical properties of the steel under different annealing processes were studied. Microstructural analysis reveals that nanoscale κ-carbides and Cu-rich particles precipitate in the austenite and ferrite of the steel in this annealing temperature range. Co-precipitation of nanoscale Cu-rich particles and κ-carbides provides an obvious increment in the yield strength. At the annealing temperature of 600 °C, both the yield strength and ultimate tensile strength of Fe-28Mn-9Al-0.8C-3Cu (wt.%) steel strip are the highest. The total elongation is 25%, which is obviously higher than that of Cu-free steel strips, for the addition of Cu reduces the large sized κ-carbides precipitated along austenite/ferrite interfaces. When the annealing temperature rises to 700 °C, the strength and ductility of the two steel strips deteriorate due to the formation of massive intergranular κ-carbides precipitated along austenite/ferrite interfaces. It can be concluded that a proper co-precipitation of Cu-rich particles and κ-carbides would improve the properties of austenite-based Fe-Mn-Al-C steel. [ABSTRACT FROM AUTHOR]

The microstructure, mechanical properties, and electrochemical performances of TiCN composite coatings were investigated. Via the modification of the C 2 H 2 /N 2 flow ratio, TiCN coatings with various C contents were synthesized by combining a cathodic arc and glow discharge technology. With a C 2 H 2 /N 2 flow ratio of 1:8, TiCN coating mainly consisted of the TiC phase. As the C 2 H 2 /N 2 flow ratio exceeded 1:4, the crystallinity of TiCN coatings deteriorated. The coexistence of the amorphous and crystalline phases was detected in TiCN coatings with a C 2 H 2 /N 2 flow ratio of 3:8. The introduction of the C element into TiCN coatings could disturb the growth orientation and induce dislocation motion, leading to an enhancive toughness and a decrease in hardness and elastic modulus. Moreover, the precipitation of amorphous C or CN x was beneficial to the corrosion resistance of TiCN coatings. This finding indicates the potential application of TiCN composite coating in corrosive environments. • A high C 2 H 2 /N 2 flow ratio favors the formation of amorphous structures in TiCN coating, and the N atoms preferred to combine with C atoms rather than Ti atoms. • The formation of amorphous structures with a high C 2 H 2 /N 2 flow ratio weakens the hardness of TiCN coating, but the toughness is strengthed. • The inert amorphous structures could endow the TiCN coating with low porosity, and enhance the corrosion resistance. [ABSTRACT FROM AUTHOR]

The microstructures and tensile mechanical properties of thin-walled Be-38 wt%Al samples produced by laser solid forming (LSF) are investigated. The results show that no cracking or significant porosity is observed in the thin-walled samples. The microstructure of the LSFed Be–Al alloy is primarily composed of columnar Be grains delineated by continuous Al networks. The columnar Be grains show almost the same crystallographic orientation, in which the preferred growth direction is the <0001> direction inclined towards the scanning direction at an angle of approximately 70°. The widths of the Be columnar grains gradually increase as the deposition height increases. The LSFed Be–Al alloy shows anisotropic tensile properties, exhibiting higher ultimate tensile strength and yield strength but smaller elongations for the longitudinal specimens compared to the transverse specimens. BeO and Al 2 O 3 particles are observed to be primarily distributed at the Be/Al interface, resulting in a lack of bonding or cracking during the tensile test. [ABSTRACT FROM AUTHOR]

• Effects of tailings fineness on CPB performances were investigated. • Tailings fineness influences CPB fluidity through changing WFT. • The UCS/UPV decreases significantly as tailings fineness increases up to 54.42%. • The UCS can be predicted directly by using pore refinement index. Mill tailings generated from the processing plant have been increasingly used in cemented paste backfill (CPB); however, the effect of their fineness (<20 μm) on the performance of CPB is still not well understood. In this study, artificial silicon tailings with various fineness, e.g., 33.9%, 44.16%, 54.42%, 64.48% and 74.94% were first prepared. Then, the effect of tailings fineness on the fluidity, unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV) and microstructural properties of CPB were evaluated. The result shows that, the increased tailings fineness decreases the fluidity of fresh CPB by lowering the water film thickness (WFT). The UCS and UPV of CPB decrease significantly as tailings fineness increases up to 54.42%. With a further increase of tailings fineness, the UCS and UPV remain constant or slightly increases. It is also found that the total porosity increases with higher tailings fineness, whereas the critical pore diameter decreases. Additionally, the UCS of CPB increases linearly with a higher pore refinement index. As a result, it will contribute to the efficient utilization of tailings waste and rational design of CPB structures. [ABSTRACT FROM AUTHOR]

The lattice structure with graded composition and microstructure in function of position, allowing for smooth transition and combination of multiple desirable features, has great prospects in various applications. Laser powder bed fusion (LPBF) is an effective approach to preparing the gradient-material lattice structure by altering the proportion of raw powder materials. In this study, in-situ TiB/Ti6Al4V gradient-material bulk samples and Schoen Gyroid scaffolds with various relative densities were manufactured by LPBF for the first time. Microstructure evolution, manufacturing quality, and mechanical responses were analyzed in detail. The results show that the graded layers exhibit good metallurgical bonding with irregular band-shaped transition zones at the interface. The in-situ synthesized TiB phase particles improve the strength and grain refinement, but decrease the dimensional accuracy and induce more defects. The elastic modulus and compressive yield strength of gradient-material lattice structures increase with the rise of the relative density. The TiB/Ti6Al4V gradient-material lattice structures have higher stiffness and strength compared with homogeneous Ti6Al4V counterparts. A combined model for predicting and designing the mechanical properties of lattice structures with graded layers is used to offer a new methodology to design complex components with multiple materials combined with superior performances. [ABSTRACT FROM AUTHOR]

In the present work, the influence of Ag 2 O content on the microstructural feature, bio-corrosion behaviour and biological property of the resultant Ag-incorporated TiO 2 micro-arc oxidation (MAO) coating is investigated. It is revealed that, with the addition of an increased amount of Ag 2 O nanoparticles (NPs) in the MAO electrolyte, a less defective Ag-incorporated TiO 2 coating with pores of decreased dimensions could be produced, which also exhibits a higher anatase-to-rutile ratio along with a lower Ag 2 O-to-Ag ratio. Further, both antibacterial capability and bone formability of Ag-incorporated TiO 2 coatings were investigated. The results show that the addition of an increased amount of Ag 2 O NPs enhances antibacterial capability of the resultant coating, which also exhibits desirable biocompatibility. This work offers a promising fabrication method for dual functional Ag-incorporated TiO 2 coating with Ag 2 O NPs as Ag source. [ABSTRACT FROM AUTHOR]

It is well known that non-linear ultrasound is sensitive to some microstructural characteristics in material. In this paper, the effect of the second phase of AI 2219-T6 alloy after heat treatment on non-linear ultrasound is studied. The non-linear ultrasonic absolute parameter β of AI 2219-T6 alloy is determined for the first time and the non-linear parameters and yield strength of each of the artificially aged specimens are measured. The experimental results show that there is a certain correlation between non-linear parameters and yield strength. Microstructural observations confirmed that those fluctuations are due to the formation and evolution of precipitates that occur in a unique precipitation sequence in this alloy These results suggest that the non-linear ultrasonic measurement can be useful for monitoring second-phase precipitation and related mechanical properties in AI 2219-T6 alloy. [ABSTRACT FROM AUTHOR]

Highlights • The compressive strength of SAAC decreased with the increase of carbonation depth. • Phase component and microstructure significantly changed with the increase of carbonation depth. • An appropriate value of the carbonated substance reaction coefficient based on experimental results was proposed for SAAC. • A practicable mathematical model displays a high potential for the estimations of carbonation rate in SAAC. Abstract Carbonation could not be ignored because of the significant deterioration of mechanical property and durability of sand autoclaved aerated concrete (SAAC). A better understanding and quantification are necessary for maintaining and repairing the existing structures of SAAC. A practicable mathematical model based on the Fick's first law was established, which was evaluated by the data of accelerated carbonation experiment. Carbonation behavior was studied by means of phenolphthalein test, SEM and XRD. Because the tobermorite generated by hydration gradually transformed into calcite, the compressive strength of samples showed an obvious decline with carbonation depth increased. Furthermore, the experimental date of B05 bulk density class SAAC samples and the calculated values of model have shown good agreements. [ABSTRACT FROM AUTHOR]

The microstructure, mechanical properties, and electrochemical performances of TiCN composite coatings were investigated. Via the modification of the C 2 H 2 /N 2 flow ratio, TiCN coatings with various C contents were synthesized by combining a cathodic arc and glow discharge technology. With a C 2 H 2 /N 2 flow ratio of 1:8, TiCN coating mainly consisted of the TiC phase. As the C 2 H 2 /N 2 flow ratio exceeded 1:4, the crystallinity of TiCN coatings deteriorated. The coexistence of the amorphous and crystalline phases was detected in TiCN coatings with a C 2 H 2 /N 2 flow ratio of 3:8. The introduction of the C element into TiCN coatings could disturb the growth orientation and induce dislocation motion, leading to an enhancive toughness and a decrease in hardness and elastic modulus. Moreover, the precipitation of amorphous C or CN x was beneficial to the corrosion resistance of TiCN coatings. This finding indicates the potential application of TiCN composite coating in corrosive environments. • A high C 2 H 2 /N 2 flow ratio favors the formation of amorphous structures in TiCN coating, and the N atoms preferred to combine with C atoms rather than Ti atoms. • The formation of amorphous structures with a high C 2 H 2 /N 2 flow ratio weakens the hardness of TiCN coating, but the toughness is strengthed. • The inert amorphous structures could endow the TiCN coating with low porosity, and enhance the corrosion resistance. [ABSTRACT FROM AUTHOR]

Laser sintering (LS) has capability of manufacturing complex structures and functional parts. However, material aging and part performance stability are still challenges to face in LS irrespective of protective atmosphere. Consequently, this work focuses on the essence of these problems and investigations on systematical mechanism of PA-12 aging and its micro-structural evolution during LS. The results show that the mechanism mainly has two opposite aspects concerning the material processability. On one hand, analogous Brill transition of peak merging, which is discovered for the first time in the powder aging process of LS PA-12 material, leads to a higher oneset melting temperature of the aged powder and broadens the sintering window more than 1 °C after 3 recycling. On the other, the existence of solid-state and melt-state polycondensation, which is proved by XPS and rheological measurements, induces the higher temperature nucleation for the aged powder and the crystallization postponement for aged LS parts detected in DSC. The effect of solid-state polycondensation reduces the crystallinity of the powder by ∼6% after 3 recycling. This mechanism is of the guiding significance for powder stability improvement and consistent control of component properties next. [ABSTRACT FROM AUTHOR]

Commercial F500 SiC powder and 6061 Al powder were chosen to fabricate the 50 vol.-% SiCp/6061Al composites via pressureless sintering. Effects of pre-treatment of the SiC powder and sintering temperature on the microstructures and properties of the composites were studied. Densification mechanism and interfacial reaction of the composites were also investigated. The results show that the composites have a high sintering ability and a low interfacial reaction activity. The density, bending strength and thermal conductivity of the composites are all sensitive to the sintering temperature. The composites sintered at 680°C are nearly fully dense and have the following optimal properties: the relative density of 98.5%, the bending strength of 495 MPa, the TC of 153 W/(m K) and the coefficient of thermal expansion of 8.1 × 10−6/°C (50–100°C), which are superior to most of the SiCp/Al composites of the similar composition reported previously. [ABSTRACT FROM PUBLISHER]

The microstructure and micropillar compression responses of thin-walled Be–Al and Be–AlSi10Mg samples, produced by laser solid forming (LSF), were investigated. Both alloys resembled typical 3-D net-shaped structures. The Be–AlSi10Mg alloy exhibited coarser Be grains embedded in the refined Al net-like matrix owing to a broader solidification region. Owing to the multi-hardening by Si and Mg alloying, the yield strength of the system significantly increased from 150 MPa to 220 MPa. In addition, the failure mode changed from plastic fracture of the Al phase in Be–Al to brittle fracture of the Be phase in Be–AlSi10Mg during microcompression. Based on the theoretical calculation of the yield strength and fracture strength, grain size refinement by the non-uniform nucleation process was dominant factor affecting the Al matrix strength increment of Be–AlSi10Mg. Meanwhile, the critical resolved shear stress of Be was smaller than the ultimate strength of the Al phase strengthened by Si and Mg in the Be–AlSi10Mg alloy. Thus, the failure preferentially occurred in the Be phase rather than the Al phase. These results suggest that improving the fracture strength of the Be phase is important for obtaining high-performance Be–Al alloys after the strengthening of the Al phase by alloying additions and artificial aging measurements. [ABSTRACT FROM AUTHOR]

• The well-bonded NiTi wall was fabricated by introducing CMT based WAAM method. • The NiTi wall exhibits mainly columnar grains with different morphologies and equiaxed grains near the top surface. • The B2 is the main constituent phase and Ti 2 Ni/Ti 4 Ni 2 O precipitates appear after deposition. • Each layer shows a one-step B2→B19′ transformation and the Ms temperature is lower than that of the as-received wire. • The mechanical properties show position dependence and reliable plasticity. Wire arc additive manufacturing (WAAM) has been proved to be a promising method to fabricate large expensive NiTi shape memory alloys with complex geometry. In this study, five layers of NiTi alloy with dimensions of 80 × 12 × 15 mm were deposited by the cold metal transfer (CMT) welding based WAAM process. The macroscopic morphology, microstructure evolution, phase transformation and mechanical properties of each layer were investigated and compared with each other. Each layer of the as-deposited NiTi wall shows a one-step B2→B19′ transformation during cooling and the martensitic transformation temperature (M s) is lower than that of the as-received wire. For the first three layers, the columnar grains growing along the building direction have a larger length-to-diameter ratio and B2 is the main constituent phase. Coarse dendritic Ti 2 Ni/Ti 4 Ni 2 O precipitates are precipitated at the interior of the grains besides grain boundaries. However, grains in the subsequent layers become finer and the region near the top surface are characterized by equiaxed grains, and elliptical Ti 2 Ni/Ti 4 Ni 2 O precipitates mainly concentrate at grain boundaries. The heat-affected zone exhibits the lowest hardness of 233.34HV, followed by a gradually increase among the as-deposited layers and the highest hardness of 331.27HV was obtained at the 5th layer. The highest ultimate tensile strength of 652.46Mpa, together with the elongation of 13.66% and recoverable strain of 2.39% was obtained in the sample which is located at 11.5 mm height away from the substrate. This research provides an innovative method and insights for additive manufacturing NiTi shape memory alloys by introducing CMT based WAAM method. [ABSTRACT FROM AUTHOR]

The Cu/Invar bi-metal matrix composites have a great potential to be used as novel electronic packaging materials. In order to clarify effects of the Invar particle size on microstructures and properties of the composites, two Invar powders of average sizes of 26 µm and 105 µm were employed to fabricated the 50 wt% Cu/Invar composites, respectively, by spark plasma sintering (SPS) at 700–800 °C under vacuum condition with a heating rate of 100 °C/min, a pressure of 50 MPa and a holding time of 1 min. The results indicate that the Cu/ fine Invar (f-Invar) composites have finer Cu grain sizes in which the f-Invar particles are semi-continuously distributed. The composites have typical characteristics of low-angle Cu grain boundaries, high-density Σ3 growth twins and Cu/Invar coherent/semi-coherent interface. On the contrary, the coarse Invar (c-Invar) particles are discontinuously distributed in the Cu/c-Invar composites, resulting in the formation of coarser Cu grain sizes, high-angle Cu grain boundaries and non-coherent Cu/Invar interface. Moreover, compared with the f-Invar particles, the c-Invar ones can not only effectively decrease the Cu/Invar interfacial area, but also prohibit the Cu/Invar interface diffusion, therefore considerably improve thermal conductivity (TC) of the Cu/Invar composites at the cost of a little reduction of tensile strength (R m). It is also clarified that properties of the Cu/Invar composites are sensitive to the sintering temperature. The 700 °C sintered 50 wt% Cu/c-Invar composite has the highest TC of 130.1 W/(m·K). It is very close to the theoretical value predicted by the Maxwell model and much superior to the TCs previously reported in the Cu/Invar composites of the similar Invar fraction. [Display omitted] • SPS technique used to fabricate the Cu/Invar composites at low temperature. • Interfacial characteristics of the composites varied with Invar particle size. • Relationships between microstructures and properties of the composites. • The highest TC among those of the composites of the similar Invar fraction. [ABSTRACT FROM AUTHOR]

Surface coatings with the improved antibacterial capability and osteogenic activity are highly favoured for titanium (Ti)-based orthopaedic implants. Herein, Ag, Zn co-modified titania was synthesized using the micro-arc oxidation (MAO) technique with Ag nanoparticles (NPs) as Ag sources and ZnO NPs as Zn sources. The synergistic effects of Ag and ZnO additions not only result in the significant modification of their existing forms, but also promote the formation of two different types of Ca P phases, namely Zn-incorporated dicalcium phosphate dihydrate (DCPD) crystal and submicron-sized amorphous Ca P phase deposition of porous appearance. Anti-corrosion, antibacterial and osteogenic experiments prove that the synthesis strategy of Ag, Zn co-modified titania provides a promising way for Ti-based bioceramic coatings for orthopaedic implants. • The Ag, Zn co-modified titania has been successfully fabricated in the electrolyte containing Ag and ZnO nanoparticles. • Zn-incorporated dicalcium phosphate dehydrate crystal and amorphous Ca P phase are formed. • The synergistic effect of Ag and ZnO enhances the corrosion resistance and biological performances of titania. [ABSTRACT FROM AUTHOR]

Abstract: Microstructure, biocorrosion behavior and cytotoxicity of an as-extruded Mg–11.3Gd–2.5Zn–0.7Zr (wt%) alloy were studied, in order to develop new biodegradable magnesium alloy. The microstructure of the as-extruded alloy mainly consists of the refinement grains, a lamellar X phase with the 14H-type long period stacking ordered (LPSO) structure in grain boundaries and the 14H-type LPSO structure within initial grains and refinement grains, and a small amount of β phase. The as-extruded alloy has high strength at room temperature. The corrosion rate in Hanks'' solution is only 0.17mm/year and the corrosion mode of the alloy is uniform corrosion, which is much better than that of as-extruded Mg–10.2Gd–3.3Y–0.6Zr (wt%) alloy. Moreover, the cell toxicity grade of the Mg–11.3Gd–2.5Zn–0.7Zr alloy is Grade 1, indicating only slightly having cytotoxicity. The desired results indicate the Mg–Gd–Zn–Zr alloy with LPSO structure will become one of novel promising high-strength biodegradable magnesium alloys. [Copyright &y& Elsevier]

Abstract: As a candidate material for high temperature applications, the Mg–10Gd–2.0Y–0.46Zr alloy may undergo the alternate loading during the service lifetime. Under the total strain-controlled triangular waveform loading, the strength and the evolution of microstructures for the alloy at 573K have been explored. The results show that the alloy presents cyclic softening characteristics at diverse total strain amplitudes. The grain boundary sliding has been detected near the cracks on the surface of the specimen, suggesting that the grain boundary sliding plays an important role in coordination deformation at 573K. Microcracks initiate mostly either at grain boundaries for lower strain amplitudes or at persistent slip bands for higher strain amplitudes, and then propagate along grain boundaries. Due to twinning shear and the dislocations slip, the precipitates in the deformation twins disintegrate to form a small equilibrium phase. The dislocation cells, small angle grain boundaries, as well as dynamic recrystallization are observed in the precipitation-free zone. [Copyright &y& Elsevier]

Abstract: Mn and Zn were selected to develop a Mg–Zn–Mn magnesium alloy for biomedical application due to the good biocompatibility of Zn and Mn elements. Microstructure, mechanical properties, corrosion properties and biocompatibility of the Mg–Zn–Mn alloys have been investigated by use of optical microscope, scanning electron microscope, tensile testing, and blood hemolysis and cell toxicity. Microstructure observation has shown that the addition of Zn and the extrusion significantly refined the grain size of both the as-cast and the extruded magnesium alloys, which mainly contributes to the high tensile strength and good elongation. Polarization test has shown Zn could accelerate the formation of a passivation film, which provides good protection to the magnesium alloy against simulate body fluid. Cell culture and hemolysis tests have shown that the magnesium alloy did not have cell toxicity, showing good cytocompatibility, but the alloy caused hemolysis to blood system. It was suggested that surface modification have to be adopted to improve the blood compatibility of the magnesium alloy for the application in blood environment. [Copyright &y& Elsevier]

The microstructure evolution of a hot extrusion (HEXed) powder metallurgy (PM) nickel-based superalloy was investigated by hot compression tests under different deformation conditions. Optical microscope (OM), electron backscatter diffraction (EBSD) technique and transmission electron microscope (TEM) were applied to investigate the effect of Zener-Hollomon (Z) parameter on the microstructure evolution and nucleation mechanisms of dynamic recrystallization (DRX). The results show the stress-strain curves of the experimental superalloy exhibit obvious characteristics of DRX. Microstructure observations reveal that with the decrease of the Z parameter, both the degree of DRX and the size of DRX grains for the experimental superalloy gradually increase. The nucleation mechanism of DRX of the experimental superalloy is related to the Z parameter. Under the condition of lower Z value, discontinuous dynamic recrystallization (DDRX) characterized by bulging of grain boundaries is the main mechanism of DRX, while continuous dynamic recrystallization (CDRX) is considered to be an auxiliary mechanism for DRX nucleation in hot deformation. The existence of twins and γ' phase also has a major effect on the DRX nucleation mechanism of the experimental superalloy. Under the condition of higher Z value, CDRX and DDRX occur simultaneously, while CDRX characterized by progressive subgrain rotation can also be regarded as an important nucleation mechanism of DRX. [Display omitted] • Four nucleation mechanisms of DRX in the PM superalloy are clarified. • DDRX is the principal nucleation mechanism of DRX for all Z parameters. • Twins and γ′ phases play significant roles in the nucleation of DRX at lower Z value. • CDRX is also an important nucleation mechanism of DRX at higher Z value. [ABSTRACT FROM AUTHOR]

The poor machinability of the high-fraction SiCp/Al matrix composites is one of the key factors that hinders its application in electronic packaging. In this study, (0−15) wt% GNFs/SiCp/6061Al matrix hybrid composites are prepared by vacuum hot pressing at 590 °C and 50 MPa with the graphene nanoflakes (GNFs) partially replacing SiCp, the microstructure and ground surface properties of the composite and their effects on the mechanical and thermal properties of the composite are studied, and the machining performance is comprehensively evaluated. The results show that the interface of the composite is well-bonded and no Al 4 C 3 products exist. With increasing GNFs content, the GNFs in the composites tend to agglomerate, the density decreases, and the damage to the ground surface and microstructure increases. Compared to the 54.2 wt% SiCp/6061Al matrix composites, the 5 wt% GNFs/48.4 wt% SiCp/6061Al matrix composites have lower strength but better thermal properties, and show lesser damage of the microstructure and lesser attenuation of the mechanical and thermal properties after grinding. However, with the further increase in the GNFs content, the SiCp crack and drop off and GNFs pull out and peel severely, leading to the greater degradation of the properties of the surface of the GNFs/SiCp/6061Al matrix composites. [Display omitted] • No Al 4 C 3 in the GNFs/SiCp/6061Al matrix composites. • Clarification of the sintering and grinding mechanisms of the composites. • The best microstructures and properties of the composites of 5 wt% GNFs after grinding. [ABSTRACT FROM AUTHOR]

In this work, a Mn-incorporated Ca-P/TiO 2 composite coating was produced through the facile one-step micro-arc oxidation (MAO) method. It is revealed that only when the concentration of Na 2 Mn-EDTA reaches 0.02 mol/L, the Ca-P phase could form on Mn-incorporated TiO 2 coating, which is associated with the combined effect of EDTA complex and Mn species. The Ca-P phase is amorphous, which may contain hydroxyapatite phases whereas the underlying Mn-incorporated TiO 2 coating contains two separate layers, including the Mn-rich outer layer and Mn-depleted inner layer. The biological investigation of the Mn-incorporated Ca-P/TiO 2 composite coating suggests that it exhibits desirable osteogenesis with certain capability to inhibit the growth of S. aureus bacteria. Hence, a promising composite coating with superior bone formability could be produced using the one-step micro-arc oxidation method in the electrolyte containing Na 2 Mn-EDTA. Unlabelled Image • A Mn-incorporated Ca-P/TiO 2 composite coating could be successfully produced through the micro-arc oxidation method. • The outer Ca-P is amorphous whereas the inner TiO 2 contains two layers with different Mn contents. • Ca-P layer forms only when the concentration of Na 2 Mn-EDTA in the electrolyte reaches at least 0.02 mol/L. • The composite coating exhibits desirable corrosion resistance and bone formability with certain antibacterial ability. [ABSTRACT FROM AUTHOR]

The microstructure and micro-mechanics around the repaired interface, and the tensile properties of laser additive repaired (LARed) Inconel 625 alloy were investigated. The results showed that the microstructure around the repaired interface was divided into three zones: the substrate zone (SZ), the heat-affected zone (HAZ), and the repaired zone (RZ). The microstructure of the SZ had a typical equiaxed crystal structure, displaying simultaneously precipitated block-shaped MC-type carbides (NbC, TiC), with bimodal sizes of approximately 10 μm and 0.5 μm and an irregularly shaped flocculent Laves phase. Recrystallization occurred in the HAZ, and led to significant grain growth; a portion of the second phase dissolved in the original grain boundaries. In the RZ, there was a columnar crystal structure, and the size increased with increasing deposition thickness. Moreover, the microstructure between the layer interface and layer interior was quite different, presenting an overlapping transition zone (OTZ), in which the dendritic structure coarsened and more Laves phase were precipitated, compared to in the layer interior. The hardness and tensile properties of the LARed samples were equivalent to those of the wrought substrate, which indicates that laser additive repairing (LAR) is a reliable repair solution for damaged and mis-machined components comprising Inconel 625 alloy. [ABSTRACT FROM AUTHOR]

A self-developed pressureless sintering and subsequent thermo-mechanical treatment process was employed to fabricate 1-5 wt% graphite nanoflakes (GNFs)/Cu matrix composites. The distribution of GNFs and GNFs/Cu interface structure, as well as mechanical and thermal properties of the composites were investigated. The results showed that the thermo-mechanical treatment can significantly improve the GNFs/Cu interface structure, as well as the densities and properties of the composites. However, the distribution orientation of the GNFs and the anisotropy of properties of the composites increase in the process. After pressureless sintering and thermo-mechanical treatment, the relative densities of the 1-5 wt% GNFs/Cu matrix composites can rise as high as 99.4%. As the amount of the GNFs is increased from 1 wt% to 5 wt%, the thermal conductivities of the composites change from 380.4 W/(m·K) to 244.4 W/(m·K) in rolling direction and from 179.3 W/(m·K) to 51.9 W/(m·K) in normal direction. The tensile strengths and the coefficients of thermal expansion of the composites change form 153 MPa to 56 MPa and from 13.5 × 10−6/K to 11.9 × 10−6/K respectively. This fully satisfies the application requirements of electronic packaging materials. Unlabelled Image • A self-developed PLS + TMT process employed to fabricate the composites • Uniform dispersion and flattening of the GNFs and well bonding interface • Enhanced properties of the composites consistent with the model prediction results [ABSTRACT FROM AUTHOR]

• A 3D bi-network of GF and NDs in composites has been designed and fabricated. • Composites with a bi-network structure exhibited higher thermal conductivity. • The thermal conductivity enhancement efficiency can be maintained up to 74.33%. • FEA was carried out to confirm the heat transfer mechanism of the bi-networks. As thermal interface materials, polymers are limited by its low thermal conductivity. In this work, a three-dimensional bi-network structure consisting of chemical vapor deposition graphene foam and close-stacked nanodiamonds was constructed in epoxy matrix via a template method. The obtained composites exhibit interesting properties: significant thermal conductivity enhanced efficiency per unit of fillers (74.33%) based on pure epoxy matrix, and excellent electrical conductivity (0.256 S/cm) compared with epoxy matrix (4.58exp-14 S/cm). Finite Element Analysis based on the design of the dual networks was carried out to confirm the heat transfer mechanism, and it is proved that composites with GF/ND bi-network have a lower temperature gradient. That provides a novel insight of improvement method for thermal conductivity by construction of a three-dimension bi-network structure. [ABSTRACT FROM AUTHOR]

The mechanical properties of high-entropy alloys (HEAs) strongly depend on their microstructural features. In this work, the phase formation and morphologies of Fe 26.7 Co 26.7 Ni 26.7 Si 8.9 B 11.0 HEAs fabricated under different undercooling levels by the drop tube technique together with subsequent quenching were investigated in detail. It was found when the droplet size decreases (i.e. the increase of the undercooling level), the grain refinement is easily achieved without any phase transformation for the present hypoeutectic HEA which is composed of the fcc dendrites and eutectic structure. After quenching under large undercooling levels, the liquid should be deeply undercooled into an asymmetric couple zone, leading to the primary formation of eutectic structure and the subsequent precipitation of the fcc dendrites. The direct product of rapid solidification after deep undercooling and subsequent recalescence may induce the decoupled eutectic growth, resulting in a transition from the regular into anomalous eutectic structures. Furthermore, the volume fractions of the eutectic structures and the fcc dendrites increase and decrease with decreasing droplet size, respectively. As a result, the Vickers hardness gradually increases with decreasing droplet size, which exhibits a linear relationship with the volume fraction of eutectic matrix. The present study may provide a simple way to tailor microstructures and mechanical properties of HEAs. • High-entropy droplet were fabricated by the drop tube technique. • Grain refinement is easily achieved during containerless solidification. • Deep undercooling induces a transition from regular into anomalous eutectic matrix. • Mechanical properties can be tailored by deeply undercooled solidification. [ABSTRACT FROM AUTHOR]