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2D‐C/HfC–SiC composites were prepared by a combination of precursor infiltration and pyrolysis (PIP) and chemical vapor infiltration (CVI). Creep tests were performed at 1100°C in air under different stress conditions. Unlike most, C/SiC and SiC/SiC ceramic matrix composites only underwent primary and secondary creep stages, and the C/HfC–SiC composites underwent tertiary creep stage in the creep process. The reason was that the mechanical properties of C/HfC–SiC materials prepared by PIP + CVI methods were different from those prepared by traditional methods. The microscopic morphological analysis of the sample fracture showed that the oxidation products SiO2 and Hf–Si–O glass phases of the HfC–SiC matrix played a crack filling role in the sample during creep. In turn, it provided effective protection to the internal fibers of the sample. The creep failure of C/HfC–SiC composites in a high‐temperature oxidizing atmosphere was caused by the oxidation of the fibers. The total creep process was dominated by the oxidation of carbon fibers. It is noteworthy that there was the generation of HfxSiyOz nanowires in the samples after high‐temperature creep. The analysis of the experimental data showed that the creep stress had a linear negative correlation with the creep life. [ABSTRACT FROM AUTHOR]

In this work, we have successfully dispersed raw graphene into an epoxy coating by a facile solution mixing method using pristine and modified quinacridone as dispersants. Through mechanical and electrochemical property tests, we found that the overall performance of the graphene/epoxy coatings prepared by combining unmodified as well as modified quinacridone was significantly better than that of the coatings prepared by using only one form of the dispersant. The epoxy coatings prepared using 0.2 wt% graphene, 0.5 wt% unmodified quinacridone, and 0.5 wt% modified quinacridone showed excellent corrosion resistance, with the impedance modulus value remaining above 1010 Ω-cm2 even after 100 days of immersion in a 3.5 wt% NaCl solution at pH = 1. The coating also exhibited excellent mechanical properties, with a tensile strength of 20.88 MPa, which is 3.7 times higher than that of the pure epoxy coating, in addition to excellent abrasion resistance and pencil hardness up to 6H. This method provides a new strategy for the preparation of high-performance graphene reinforced organic coatings. • Graphene/epoxy coatings combining covalent and non-covalent modified quinacridone optimized the comprehensive properties. • Covalent modification of quinacridone improved the interfacial bonding between unoxidized graphene and epoxy resin. • Covalent modification destroyed the planar structure of quinacridone and its π-π adsorption with graphene. [ABSTRACT FROM AUTHOR]

The early corrosion control of biomedical magnesium alloy is an important measure to determine its good performance during implantation into human body. The deposition of calcium phosphate biological coating is the most effective solution at present. In this paper, hydroxyapatite (HAP) coating was hydrothermal synthesized on the surface of AZ31B magnesium alloy, and the influence mechanism of hydrothermal synthesis temperature, time and solution concentration was investigated. The synthesis conditions and deposition mechanism of hydroxyapatite coating without DCPA (CaHPO 4) were proposed. The surface morphology of the coating was observed by field emission electron scanning microscope (FESEM). The types and contents of microelements in the material were analyzed by energy disperse spectroscopy (EDS). Fourier transform infrared spectroscopy (FTIR) was used to analyze the functional group information of the coating surface. The corrosion resistance of different experimental groups was studied by electrochemical test. The results showed that when the calcium phosphate solution concentration was 0.1 ​mol/L and the calcium/phosphorus ratio was 1.67, the coating had better morphology structure and corrosion resistance, and the calcium/phosphorus ratio of HAP crystals reached 1.58, the epit of the prepared AZ31B-HAP coating by bare metal increased from −1.51 ​V to −1.18 ​V, the impedance value reached 1.0 ​× ​105 ​Ω▪cm2, and the early corrosion of magnesium alloy substrate was effectively delayed. [Display omitted] • The effects of hydrothermal time and ion concentration on the surface morphology of the coating were investigated. • By adding calcium chelating agents, controlling the supersaturation of HAP, a flake HAP coating structure was formed. • A deposition mechanism model of double-layer coating structure based on HAP coating was proposed. [ABSTRACT FROM AUTHOR]

In this article, polyvinylpyrrolidone (PVP) was used for the noncovalent modification on the surface of graphene. Compared with covalent modification, this method maintained the original structure of graphene layers, thereby maximizing the original properties of graphene. The π–π noncovalent bond was formed between PVP and graphene by X-ray photoelectron spectroscopy analysis, indicating that PVP successfully modified graphene. The thickness of graphene layer was measured by atomic force microscopy, which showed that the distance between graphene layers was increased by 5–6 nm, and the stability of the modified graphene in N, N -dimethylformamide was remarkably improved. The obtained composite coating by combination of the modified graphene and the epoxy resin was subjected to electrochemical impedance test to obtain the best anticorrosive effect of the coating with the graphene content of 0.3 wt%. The results showed that the addition of graphene to the epoxy resin could effectively improve the anticorrosive effect. Meanwhile, the good electrical conductivity allowed the electrons which lost from the substrate to led to air or saline rapidly, thereby reducing the combination of iron ions with oxygen and the generation of corrosion products (iron oxides). [ABSTRACT FROM AUTHOR]

• Selective laser melting tungsten with a relative density of 98.71% was obtained firstly. • Coarse columnar grains changed to fine grains with increasing laser scan speed. • Compressive strength and thermal conductivity were 1523 MPa and 148 W/mK. High-density pure tungsten (W) fabricated by selective laser melting (SLM) has been considered as a substantial challenge due to its high melting point of 3410 °C. In this study, near fully dense W samples with a relative density of 98.71% were obtained for the first time through a series of optimization experiments during the SLM process. The characteristics of the surface and the formation mechanism of the micro defects were systematically elucidated. Additionally, it was found that the typical microstructures of horizontal and vertical planes experienced successive changes, where coarser columnar grains changed to uniform finer grains when increasing the laser scan speed from 50 mm/s to 400 mm/s. The compressive strength, micro hardness and thermal conductivity of the optimal SLM sample was improved to 1523 MPa, 428 HV 3 and 148 W/m·K, which were superior to the sample produced by the conventional methods. The relationship of processing parameters to the surface morphology and microstructure evolution and material properties associated with fusion reactors was established in order to optimize the performance of SLM pure W and explore the possibility of further application in fusion reactors. [ABSTRACT FROM AUTHOR]

[Display omitted] • We prepared one luminescent, transparent and self-healing organogel. • The organogel has excellent mechanical properties and self-healing performance. • The luminescence of organogel is stable in cold or hot environments. • And the organogel could be as one flexible sensor because of Na+ and. C 20 H 14 O 7 2 - Perovskites were widely used as the light-emission sources of luminescent elastomers in some fields. But instability, toxicity and inhomogeneity in polymers can be considered as tricky problems in the field of luminescent materials. In this paper, we have reported one luminescent organogel sensor with various admirable characters such as high elasticity, stretchable, transparent and luminescent. The organogel has a favorable self-healing performance (healing efficiency: ∼100%) benefit from borate ester bonds, hydrogen bonds and Van der Waals' forces (Debye forces). And the organogel possesses admirable mechanical properties, such as high toughness of > 1000 kJ/m3, high fracture strength of > 400 kPa, while being highly resilient (recuperative rate: 100%). In addition, the organogel can be applied as one sports sensor to monitor the states of motion thanks to Na+ and 3-oxospiro[2-benzofuran-1,9′-xanthene]-3′,6′-diolate ( C 20 H 14 O 7 2 - ) mobility in the organogel. This strategy mentioned above not only can enrich synthetic methods of the functional organogels, but also offered one novel elastomer that can be applied in the fields of e-skin and soft robots. [ABSTRACT FROM AUTHOR]

S136 mould steel with excellent corrosion resistance has been widely applied in the mould industry. However, in order to meet the increasing demands of injection products with complex structure and high quality, selective laser melting (SLM) as a novel manufacturing method is chosen due to its rapid fabricating parts with complex geometric shapes. Further, it is essential to enhance their hardness and wear property to prolong the service life of injection mould. In this work the reinforced S136 mould steel with different TiB 2 contents (0, 0.5, 1.5, 2.5 wt%) are fabricated by SLM. The optimal TiB 2 content is determined to be 0.5 wt%, which the SLM S136 composites show the finest grains and have an enhanced tensile strength (982.8 Mpa), an elevated micro-hardness (761.5 Hv), a reduced coefficient of friction (0.6489) and a considerably low wear rate (0.152 × 10 −4  mm 3 /N m). Here we demonstrate that these superior performances benefited from the novel microstructure, that is, the dispersed TiB 2 nanoparticles bonded with each other in a highly homogeneous way to form refined, continuous and well-distributed ring-like structures, which were comprised of thin “metal-ceramic” interface along the grain boundaries. It mainly contributed to the grains refining and grain boundaries strengthening. [ABSTRACT FROM AUTHOR]

The TiAl/TiB 2 metal matrix composites (MMCs) are fabricated by selective laser melting (SLM), and the effects of scan line spacing on the grains feature, crystallographic texture, phases evolution mechanism and nanohardness have been systematic studied. With the increase of scan line spacing, relatively coarse grains with average grain size of 4.9 ± 0.2 μm and strong ( 0001 ) orientation gradually transforms into refined grains with average grain size of 4.2 ± 0.1 μm and dominated ( 11 2 ¯ 1 ) and ( 01 1 ¯ 1 ) orientations during the SLM process. The SLM-processed TiAl/TiB 2 MMCs samples are dominated by high-angle grain boundaries (HAGBs) and α 2 phase, with the increase of scan line spacing from 80 μm to 140 μm, both the volume fraction of HAGBs and α 2 phase decrease. During the SLM process, the phases evolution mechanism of TiAl/TiB 2 MMCs can be expressed as: (200)β first transformed to (11 2 ¯ 0)α 2 , (20 2 ¯ 0)α 2 and (110)γ, then the TiB 2 , residual B 2 and incompletely transformed γ phases randomly distribute in the α 2 matrix, and the orientation relationship of the α 2 , γ, B 2 and TiB 2 phases can be concluded as: ( 11 2 ¯ 0 ) α 2 // ( 110 ) B 2 // ( 110 ) γ// ( 110 ) TiB 2 . Besides, there are some TiB phase in the TiAl/TiB 2 MMCs which is induced by the Ti + TiB 2 → 2TiB reaction during SLM. The TiAl/TiB 2 MMCs samples show an ultra-high nanohardness ranging from 8.6 ± 0.4 GPa to 9.4 ± 0.5 GPa with the increase of scan line spacing, which is superior than that of the TiB 2 reinforced TiAl alloy counterpart (6.7 ± 0.4 GPa) fabricated by traditional roll bonding. [ABSTRACT FROM AUTHOR]

C f @PyC/SiC composites, using needle-punched preforms, 3D orthogonal woven preforms and 3D 4-step braided preforms (braiding angles of 10°, 20° and 30°) as the reinforcement, were obtained through chemical vapor infiltration (CVI) method. The tensile strength before and after oxidation of the composites were investigated, and the microstructure, appearance of fracture and phase component of the composites were also analyzed. The results show that the mechanical properties and oxidation resistance of composites are greatly affected by the preform structures. The tensile strengths of 3D 4-step braided composites with the braiding angle of 10° are the best among all composites before and after oxidation, which are 266.40 ± 16.98 MPa and 238.66 ± 14.98 MPa. Before oxidation, the fibers and matrix at the fracture of 3D 4-step braided composites are in staggered distribution. The mechanical enhancement mechanisms of composites such as crack deflection, interface debonding and fiber pull-out, were beneficial to good performance and excellent mechanical properties. After oxidation, the deflection and branching effects of the interface on the crack are not fully manifested, and enhancement and toughening mechanisms are not fully played due to the oxidation of the carbon fiber and the PyC interface. • C f @PyC/SiC composites with five structure preforms were prepared by CVI method. • The tensile strength of 3D 4-step braided composites with braiding angle of 10° is the highest. • The tensile strength retention rate of 3D 4-step braided composites is around 90 %. [ABSTRACT FROM AUTHOR]

Novel binder-coated Al 2 O 3 sands were prepared for selective laser sintering (SLS) to manufacture complex sand moulds for metal casting. The solidification mechanisms of the coated sands during the SLS and post-curing processes were provided, and effects of binder content, raw sand type and post-curing parameters on the strength and gas evolution were investigated. At the same binder content, the strength of the Al 2 O 3 sand SLS specimen is much higher than that of commonly used quartz sand. Therefore, the binder-coated Al 2 O 3 sands are very suitable for building large sand moulds with thin walls and delicate structures. On the other hand, to meet the same strength requirement for metal casting process, the Al 2 O 3 sands need less binder content, consequently reducing gas evolution and thus improving the quality of final castings. Finally, a large sand mould for casting a complex six-cylinder diesel engine cylinder head was successfully manufactured by the SLS of the binder-coated Al 2 O 3 sands, and the final casting with the surface quality and dimensional accuracy meeting the specific design requirements was obtained. The materials and method proposed in this paper not only shortened the trial production cycle of the six-cylinder engine from five months of the traditional casting method to 10 days, but also reduced the cost and improved the casting quality. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) manufactures components through the overlapping of multi-track and multi-layer molten pools of metal powders, resulting in two types of molten pool boundaries (MPBs), "layer-layer" and "track-track" MPBs, remaining in SLM parts. The microstructure of MPBs exhibits a complex and regular spatial topological structure. There is a coarse grain zone below the MPBs and nonmetallic elements (C, O, Si) near the MPBs are in an unstable state. Long and thin columnar grains with the same orientations distribute on two sides of the "layer-layer" MPBs, whereas the columnar grains on both sides of "track-track" MPBs have different orientations. The "track-track" MPBs are short and intersect with "layer-layer" MPBs at some points and form acute angles, where cracks are initiated when applied with external loads. The effect of the MPBs on microscopic slipping, macroscopic ductility and fracture mechanism of the SLM parts made along different directions, which were exerted a tensile loading in the as-built condition without heat treatment, was analyzed and evaluated using slip theory and experiments. The results reveal that the MPBs have a significant impact on the microscopic slipping at the loading, macroscopic plastic behavior and fracture mode, and are one of the main reasons for the obvious anisotropy and low ductility of SLM parts. [ABSTRACT FROM AUTHOR]

Abstract: Bending creep test (based on overhang beam geometry) is investigated by incorporating the important contribution of residual stress. Finite element simulations considering the residual stress is employed to investigate the residual stress behavior of bending creep specimen. We propose several methods to determine the creep parameters directly from the bending creep tests. We considered two cases of residual stress, one is tensile residual stress. The other is compressive residual stress. The present work may shed some light on the influences during bending creep, as well as provide an efficient way to determine material residual stress characteristics. [Copyright &y& Elsevier]

Abstract: The purpose of the present work is to build the relationship between impression creep and conventional uni-axial tensile creep in determining crystallographic creep parameters for face centered cubic (FCC) nickel-based single crystal superalloys. To this aim, the impression creep performed on [001]-, [011]-, and [111]-oriented nickel-based single crystal superalloys were respectively investigated and the data was compared with those obtained with uni-axial tensile creep counterparts. It shows that the determination of crystallographic creep stress exponent is independent of crystallographic orientations, and the results agree reasonably well between impression creep and uni-axial tensile creep. However, some reveres dependence of crystallographic orientation was observed between impression creep and uni-axial tensile creep, such as the steady-state punch velocity for impression creep and steady-state elongation rate for uni-axial tensile creep, and this induced different stress conversion factors among different crystallographic orientations. [Copyright &y& Elsevier]

Multifunctional intrinsic self-healing polymers (ISP) are gaining increasing attention these days, and many studies have been devoted to solving the conflict between achieving high mechanical polymer strength and active polymer chain diffusion. In this research, we developed an optimized self-healing composite coating by adding Benzotriazole (BTA) loaded nano silica (SiO 2 @BTA) to a dynamic cross-linked Polydimethylsiloxane (PDMS) network，which allows substantial and fast healing of the material integrity upon damage due to the hydrogen interaction between urea and BTA. BTA leaching tests demonstrated a longer release profile during the coating service life and corrosion tests in a 3.5 wt% NaCl aqueous solution indicated that the SiO 2 @BTA modified PDMS coating shows enhanced corrosion protection of carbon steel upon coating damage. Moreover, after addition of SiO 2 @BTA, the material failure strength increased from ~1.5 MPa to ~5.5 MPa, and the healing efficiency increased from ~59% to ~90% for 24 h healing at room temperature. Above all, this research provides an intrinsic self-healing coating design method to improve the mechanical strength and the self-healing ability of the ISP as well as enhancing the coating's corrosion protection ability. [Display omitted] • Self-healing coatings were obtained by adding SiO 2 @BTA to reversibly silicone matrix. • Interaction between urea and BTA accounts for the optimized self-healing process. • Mechanical strength and self-healing property can be improved simultaneously. • The coating exhibits effective corrosion protection ability upon mechanical damage. [ABSTRACT FROM AUTHOR]

Nickel-titanium alloys have been widely used in biomedical, aerospace and other fields due to their shape memory effect, superelastic effect, as well as biocompatible and elasto-thermal properties. Additive manufacturing (AM) technology can form complex and fine structures, which greatly expands the application range of Ni-Ti alloy. In this study, the development trend of additive manufactured Ni-Ti alloy was analyzed. Subsequently, the most widely used selective laser melting (SLM) process for forming Ni-Ti alloy was summarized. Especially, the relationship between Ni-Ti alloy materials, SLM processing parameters, microstructure and properties of Ni-Ti alloy formed by SLM was revealed. The research status of Ni-Ti alloy formed by wire arc additive manufacturing (WAAM), electron beam melting (EBM), directional energy dedication (DED), selective laser sintering (SLS) and other AM processes was briefly described, and its mechanical properties were emphatically expounded. Finally, several suggestions concerning Ni-Ti alloy material preparation, structure design, forming technology and forming equipment in the future were put forward in order to accelerate the engineering application process of additive manufactured Ni-Ti alloy. This study provides a useful reference for scientific research and engineering application of additive manufactured Ni-Ti alloys. [ABSTRACT FROM AUTHOR]

AS41 magnesium alloy possesses outstanding performance features such as light weight, high strength to toughness ratio and excellent heat resistance due to the addition of Si element, while traditional casting methods are prone to inducing large grain size and coarse Mg2Si phase. In this study, we first reported utilizing the selective laser melting (SLM) technique, fabricating AS41 samples and exploring the effect of laser energy densities on the metallurgical quality by characterizing and investigating the microstructure and mechanical properties. Results showed that the optimal laser energy density range was 60 to 100 J/mm3. Average grain size of only 2.9 μm was obtained with weak texture strength of 1.65 in {0001} orientation. Meanwhile, many dispersed secondary β-Mg17Al12 and Mg2Si phases were distributed inside the α-Mg matrix. It was confirmed that the SLM process introduced more grain recrystallization, inducing giant high-angle grain boundaries (HAGBs) and hindering the movement of dislocations, therefore forming dislocation strengthening while achieving grain refinement strengthening. Finally, three times the ultimate tensile strength of 313.7 MPa and higher microhardness of 96.4 HV than those of the as-cast state were obtained, verifying that the combined effect of grain refinement, solid solution strengthening and precipitation strengthening was responsible for the increased strength. This work provides new insight and a new approach to preparing AS41 magnesium alloy. [ABSTRACT FROM AUTHOR]

To predict oxidative damage of interfaces and fibers under high temperature aerobic environment and mechanical strength of composites before and after oxidation, oxygen permeation mass transfer modeling and onion-like micromechanical modeling of multilayered interface were proposed. The oxygen mass transfer theory and oxidation damage theory of PyC interface were used to establish the two models. The oxidative damage of PyC interface was extended to (PyC-SiC) n multilayered interface, and transformation of SiC phase and microcracks caused by thermal mismatch were also considered. The law of oxygen permeation mass transfer and the evolution of fiber oxidative damage in the "Carbon fiber/(PyC-SiC) n multilayered interface" region were revealed. The mechanical strength of composites under different interface layers was researched, resembling an onion-like wrapping in layers from the core outwards. Furthermore, C f @(PyC-SiC) n /SiC(n = 1/2/3/4) composites were prepared by chemical vapor infiltration (CVI) method. The mechanical properties of the composites were tested before and after oxidation. A comparison was made between the experimental and predicted tensile strengths before and after oxidation. The predicted results of tensile strength were found to be in good agreement with the experimental ones. In addition, the results show that PyC-SiC multilayered interface has a positive effect on the tensile strength of the composites, mainly as the cracks are deflected and branched by the multilayered interface to promote the multistage pull-out of the fibers. With the increase of interface number, the oxygen diffusion path was lengthened and zigzagged, reducing the oxidative damage of fiber and interface. [ABSTRACT FROM AUTHOR]

Amphiphilic block copolymer (PTFEMA- co -PSBMA) functionalized silica (SiO 2) nanoparticles of SiO 2 - g -(PTFEMA- co -PSBMA) were prepared by empolying surface-initiated atom transfer radical polymerization (SI-ATRP) technique. Then the SiO 2 -g-(PTFEMA- co -PSBMA) nanoparticles are physically blended with polydimethylsiloxane (PDMS) matrix to prepare one kind of novel fouling release antifouling coating. • Preparation of a new type of functional silica nanoparticle (SiO 2 - g -(PTFEMA- co -PSBMA)). • SiO 2 - g -(PTFEMA- co -PSBMA) and PDMS can be physically blended to prepare a functional antifouling coating. • The functional antifouling coating exhibits excellent antifouling performance along with good fouling release performance. • The functional antifouling coating can still maintain good antifouling performance even if it suffers heavy surface wear. Ocean-going ships, deep-sea equipment, coastal facilities, and other underwater surfaces are often attached to and fouled by marine microorganisms, animals, and plants, leading to damage, equipment failure or major economic losses in severe cases. Therefore, it is of great significance to take measures to prevent marine biofouling. To date, no single eco-friendly technology has been developed to achieve good antifouling effects. Therefore, the combination of multiple antifouling factors is still one of the main strategies to strengthen antibiofouling performance. In this paper, amphiphilic block copolymer (PTFEMA- co -PSBMA) functionalized silica (SiO 2) nanoparticles of SiO 2 - g -(PTFEMA- co -PSBMA) were prepared by surface initiated atom transfer radical polymerization (SI-ATRP), and then they were physically blended with polydimethylsiloxane (PDMS) matrix to prepare one kind of novel antifouling coating. Compared with control silicone rubber coating and bare SiO 2 -dopped silicone rubber coating, the experiment results show that the diatom density on the surface of the copolymer functionalized silica nanoparticle-dopped coating is reduced by approximately 30 % and 50 %, respectively. Furthermore, upon employing washing process, it is found that the highest removal rate of diatoms on the surface of the copolymer functionalized silica nanoparticle coating is 50 %, which is approximately twice the removal rate of the unmodified SiO 2 silicone rubber coating. Finally, it is found that the surface of the copolymer functionalized silica nanoparticle coating still has good antifouling and fouling release properties upon encountering wear test. These above results prove that the coatings with functionalized nanosilica nanoparticles have better antifouling performance. Current strategy in this work provides a new route for developing environmentally friendly fouling-releasing antifouling coatings. [ABSTRACT FROM AUTHOR]

• NiTi shape memory alloys with different Ni atomic percentages were formed by L-PBF. • Ni content affected the Ms temperature and phase composition of L-PBF NiTi alloy. • An atomic percentages phase transition temperature equation was proposed firstly. • L-PBF NiTi alloy showed SME with lower Ni content, otherwise superelasticity. In this study, three NiTi shape memory alloys with different Ni atomic percentage (50.73, 50.93 and 51.27 at%) were fabricated by laser powder bed fusion (L-PBF). The effect of Ni content on phase transformation temperature, phase composition, microstructure, mechanical properties and deformation recovery phenomenon of NiTi alloy were systematically investigated. The results indicated that the Ni content of L-PBF NiTi alloy affected Ms temperature and further affected phase composition. According to the effect of Ni contents on phase transition temperatures, a relationship between them was fitted. Subsequently, an equation defining the atomic percentage phase transition temperature is proposed. The effect of Ni content on grain orientation, texture and grain size was limited, but it had an effect on hardness and compression performance. L-PBF NiTi sample displayed shape memory effect with the lower Ni content (50.73 at%), however, showed superelasticity phenomenon with the higher Ni content (50.93 and 51.27 at%). Therefore, transformation temperature and deformation recovery phenomenon of L-PBF NiTi alloy could be tailored by adjusting Ni content to achieve special applications in the future. [ABSTRACT FROM AUTHOR]

• It studied the effect of TiC on microstructure and mechanical property of SLM Al. • An ultrafine eutectic microstructure was observed in the spherical Al matrix. • Solubility reduced and network microstructure became coarser with TiC increasing. • Al-15Si/1% TiC has high property due to particle reinforcement and ring structure. Selective laser melting (SLM) has been regarded as one of the most effective powder-based additive manufacturing (AM) methods for metal parts. The present study systematically investigated the influence of adding TiC content on the microstructural evolution and mechanical property of SLM hypereutectic Al-15Si alloy. Due to the high cooling rate during the SLM process, an ultrafine eutectic microstructure was observed in the form of spherical sub-micro-sized network eutectic Si embedded in the Al matrix, resulting in high tensile properties (398 MPa, 2.6%) and micro-hardness (154 Hv) for Al-15Si alloy. The solubility of Si atom in the Al matrix was calculated to be 9.37 at%. With increasing the TiC content from 1.0, 2.5 to 10 wt%, the solubility decreased rapidly and the network eutectic microstructure became coarser, precipitating out some small Si particles finally. That was because the TiC addition changed the thermodynamics of the melt pool, especially changed the undercooling degree in the SLM process. Attributing to the effect of eutectic microstructural evolution and the particle reinforcement, the micro-hardness was down firstly (146 Hv) and then up (177 Hv). Inversely, the tensile property firstly rose (578 MPa 7.86%) then descended (313 MPa, 2.24%). This study indicated that the microstructure and mechanical properties of SLM Al-15Si alloy can be tailored by suitable addition of TiC content. [ABSTRACT FROM AUTHOR]

• Nano-TiB 2 reinforced S136 mould steel composites were fabricated by SLM. • Effects of TiB 2 on microstructures and corrosion property of composites were studied. • The SLM composites possessed finer grains compared to the SLM pure S136. • Higher electrochemical property and less weight loss was obtained for SLM composites. The S136 mould steel matrix with varying mass fractions of TiB 2 (0–2.5 wt%) were produced by selective laser melting (SLM). This study mainly focused on the influence of TiB 2 content on the microstructure and corrosion property of the S136 composites in detail. The electrochemical method and weight loss test in the 3.5 wt% NaCl solution and 6 wt% FeCl 3 solution were conducted to determine the corrosion resistance of the composites. Results demonstrated that the SLM 0.5 wt% TiB 2 /S136 composites possesses higher corrosion and pitting potentials as well as lower corrosion current density and weight loss compared to that of other samples owing to the existence of the finer grains and TiO 2 passive film. Furthermore, the corrosion property of the composites decreased with the gradually increasing TiB 2 content associating with more defects and galvanic cells, which was detrimental to the corrosion property. Herein, the corrosion mechanism of the SLM TiB 2 /S136 composites was also deeply discussed in this paper. [ABSTRACT FROM AUTHOR]

In this work, a novel approach combining liquid deposition with selective laser melting (SLM) is used for fabricating reduced graphene oxide (RGO)/S136 metal matrix composites (MMCs). The grain sizes, crystallographic textures, phase compositions and mechanical properties can be tailored by controlling the RGO content in the RGO/S136 MMCs. The results show that the average grain size reaches its smallest size of 0.75 μm when 0.1 wt% RGO was added to the RGO/S136 MMCs. As the RGO content is increased from 0 wt% to 0.5 wt%, a continuous transition of the grains from the (001) orientation to the (101) and (111) orientations is observed. In addition, the cellular dendritic grains transform into equiaxed fine grains with increasing RGO content. The SLM-prepared RGO/S136 MMCs are dominated by high-angle grain boundaries (˃15°) and the martensite (bcc) phase. The hardness, ultimate tensile strength and yield strength of the SLM RGO/S136 MMCs exhibit trends that initially increase and then decrease, with maximum values of 580.6 HV, 535.3 MPa and 515.8 MPa, respectively. This paper highlights the possibility of controlling the RGO content to achieve the desired microstructural characteristics and mechanical properties of RGO/S136 MMCs fabricated by the SLM process. Unlabelled Image • The fully dense RGO/S136 composites via molecular-level mixing were firstly fabricated by selective laser melting. • EBSD patterns revealed the refined grain and tailored microstructure for SLM RGO/S136 composites. • SLM RGO/S136 composites with 0.1 wt% RGO exhibited maximum tensile properties and hardness. [ABSTRACT FROM AUTHOR]

• Laser-scan mode affects grain structure and texture types. • The unidirectional scanning mode promotes stronger texture in building direction. • Unidirectional scanned samples exhibit phase transformation under magnetic field. • The magnetic-field-induced strain in Ni-Mn-In samples can reach 820 ppm. Dense polycrystalline Ni-Mn-In alloy specimens were fabricated by utilizing two laser scanning strategies of laser powder bed fusion (L-PBF) technology for the first time. The effect of scanning strategies on the microstructure, crystals texture and magnetic-field-induced strain (MFIS) were investigated systematically. The results showed that the uniformly sized grains were formed in samples with unidirectional scanning strategy, while the bidirectional scanning strategy leads to a bimodal distribution of grains. The MFIS value in unidirectional strategy increased over twofold, rising from 403 ppm to 820 ppm. This work opens a new insight into regulating process parameters and customizing the microstructure and overall magnetic properties of Ni-Mn-In alloys in the additive manufacturing field. [ABSTRACT FROM AUTHOR]

Micron-sized particles are prone to deposit on smooth surfaces. A micron-sized particle collision-deposition model including the effects of electrostatic forces, integrated with the factors of particle size, material properties, elastic–plastic deformation, particle charging, surface roughness, and van der Waals forces, is proposed. The effects of the electrostatic forces on the critical deposition velocity, collision duration, and coefficient of restitution (COR), which is the ratio of particle velocity after and before the collision, are investigated for 1–20 μm sand particles colliding with glass, steel, and aluminum alloy surfaces. The results show that the electrostatic forces of sand particles are approximately 106–108 times their gravity and increase the impact duration. Moreover, these forces increase the critical deposition velocity by 2.32–6.89% for the glass surface and decrease the COR by 0.6–3.5% for the three surfaces, while the particle size is below 20 μm and the roughness is 1 nm. The electrostatic forces ranked from the maximum to the minimum are those of the aluminum alloy, steel, and glass surfaces for the same particle size and surface roughness. The developed model can perfect the theory of particle flow and gas-particle two-phase flow. [ABSTRACT FROM AUTHOR]

This paper investigated the relationship between crystallographic-orientation and micro-cracks of Ti-47Al-2Cr-2Nb alloy. Results show that the crystallographic-orientation is adverse in the nearly γ microstructure and becomes advantageous in the fully lamellar microstructure. Therefore, micro-cracks largely generate in the nearly γ microstructure and much decrease in the fully lamellar microstructure. [ABSTRACT FROM AUTHOR]

Powder-layering is an essential process of selective laser melting (SLM), but the underlying mechanisms of powder movement and packing at particle scale is unclear. Based on discrete element method (DEM), this study proposed a numerical model to investigate the flowing behavior of powder layered by a blade, where the contact force and cohesion force between individual particles were considered. DEM simulations gave visual morphologies of the flow profiles and velocity fields for powder-layering at particle scale, as well as the relationships between the quality of powder bed and the layering parameters. The model was validated by experiment results in terms of the macroscopic profiles of powder during layering, showing good prediction accuracy. Then, dynamic repose angle (DRA) and mass flow rate (MFR) were defined to make quantitative evaluation on the powder flow. Preliminary research shows that, the powder fluidity increases with the decreasing of particle friction coefficients, resulting in a denser and more uniform powder bed. The decreasing of particle radius R over the range of R > 21.8 μm can benefit the powder fluidity. However, when the particle radius decreases in the range of R < 21.8 μm, the weight of cohesion force rises and thus makes the powder fluidity worse. The increase of layering speed enhances the dilation of moving particles, and the decrease of layering height intensifies the local force-arches in particles. These will reduce the continuity and stability of the powder flow and is unfavorable for improving the density or uniformity of the layered powder bed. [ABSTRACT FROM AUTHOR]

Manufacturing abrasion‐resistant superhydrophobic matters is challenging due to the fragile feature of the introduced micro‐/nanoscale surface roughness. Besides the long‐term durability, large scale at meter level, and 3D complex structures are of great importance for the superhydrophobic objects used across diverse industries. Here it is shown that abrasion‐resistant, half‐a‐meter scaled superhydrophobic objects can be one‐step realized by the selective laser sintering (SLS) 3D printing technology using hydrophobic‐fumed‐silica (HFS)/polymer composite grains. The HFS grains serve as the hydrophobic guests while the sintered polymeric network provides the mechanical strength, leading to low‐adhesion, intrinsic superhydrophobic objects with desired 3D structures. It is found that as‐printed structures remained anti‐wetting capabilities even after undergoing different abrasion tests, including knife cutting test, rude file grinding test, 1000 cycles of sandpaper friction test, tape test and quicksand impacting test, illustrating their abrasion‐resistant superhydrophobic stability. This strategy is applied to manufacture a shell of the unmanned aerial vehicle and an abrasion‐resistant superhydrophobic shoe, showing the industrial customization of large‐scale superhydrophobic objects. The findings thus provide insight for designing intrinsic superhydrophobic objects via the SLS 3D printing strategy that might find use in drag‐reduce, anti‐fouling, or other industrial fields in harsh operating environments. [ABSTRACT FROM AUTHOR]

Purpose Selective laser melting (SLM) is an additive manufacturing process suitable for fabricating metal porous scaffolds. The unit cell topology is a significant factor that determines the mechanical property of porous scaffolds. Therefore, the purpose of this paper is to evaluate the effects of unit cell topology on the compression properties of porous Cobalt–chromium (Co-Cr) scaffolds fabricated by SLM using finite element (FE) and experimental measurement methods.Design/methodology/approach The Co-Cr alloy porous scaffolds constructed in four different topologies, i.e. cubic close packed (CCP), face-centered cubic (FCC), body-centered cubic (BCC) and spherical hollow cubic (SHC), were designed and fabricated via SLM process. FE simulations and compression tests were performed to evaluate the effects of unit cell topology on the compression properties of SLM-processed porous scaffolds.Findings The Mises stress predicted by FE simulations showed that different unit cell topologies resulted in distinct stress distributions on the bearing struts of scaffolds, whereas the unit cell size directly determined the stress value. Comparisons on the stress results for four topologies showed that the FCC unit cell has the minimum stress concentration due to its inclined bearing struts and horizontal arms. Simulations and experiments both indicated that the compression modulus and strengths of FCC, BCC, SHC, CCP scaffolds with the same cell size presented in a descending order. These distinct compression behaviors were correlated with the corresponding mechanics response on bearing struts. Two failure mechanisms, cracking and collapse, were found through the results of compression tests, and the influence of topological designs on the failure was analyzed and discussed. Finally, the cell initial response of the SLM-processed Co-Cr scaffold was tested through the in vitro cell culture experiment.Originality/value A focus and concern on the compression properties of SLM-processed porous scaffolds was presented from a new perspective of unit cell topology. It provides some new knowledge to the structure optimization of porous scaffolds for load-bearing bone implants. [ABSTRACT FROM AUTHOR]

Objective: Prevention of fragility fractures is one of the public health priorities worldwide, whilst the incidence of osteoporotic vertebral compression fractures (OVCF) continues to rise and lacks the corresponding accurate prediction model. This study aimed to screen potential causes and risk factors for primary non‐traumatic osteoporotic vertebral compression fractures (NTOVCF) in the elderly by characterizing a patient population with NTOVCF and comparing it with a population of osteoporotic patients. Methods: Between January 2013 and January 2022, 208 elderly patients with unequivocal evidence of bone fragility manifested as painful NTOVCF were enrolled, and compared with 220 patients with osteoporosis and no fractures. The demographic data, bone turnover markers, blood routine, serum biochemical values, and radiological findings were investigated. Differences between the fracture and non‐fracture groups were analyzed, and variables significant in univariate analysis and correlation analysis were included in the logistic analysis to build the risk prediction model for osteoporotic vertebral fractures. Univariate analysis using student's t‐tests for continuous variables or a chi‐squared test for categorical variables was conducted to identify risk factors. Results: No significant differences were revealed regarding age, gender, BMI, smoking, alcohol consumption, blood glucose, propeptide of type I procollagen (P1NP), and N‐terminal middle segment osteocalcin (N‐MID) (P > 0.05). Parathyroid Hormone (PTH), 25(OH)D, serum albumin (ALB), hemoglobin (HB), bone mineral density (BMD), and cross‐sectional area (CSA) of the paraspinal muscle in the fracture group were significantly lower than those in the control group; however, b‐C‐terminal telopeptide of type I collagen (β‐CTX), total cholesterol (TC), high‐density lipoprotein cholesterol (HDL‐C), non‐prostatic acid phosphatase (NACP), and fatty degeneration ratio (FDR) were significantly higher than those in the control group (P < 0.05). Logistic regression analysis showed that ALB, HB, CSA, and BMD were negatively correlated with NTOVCF, while β‐CTX, HDL‐C, NACP, and FDR were positively correlated with NTOVCF. Conclusion: Decreased physical activity, anemia, hypoproteinemia, imbalances in bone metabolism, abnormal lipid metabolism, and degenerative and decreased muscle mass, were all risk factors for OVCF in the elderly, spontaneous fractures may be the consequence of cumulative declines in multiple physiological systems over the lifespan. Based on this risk model, timely detection of patients with high OVCF risk and implementation of targeted preventive measures is expected to improve the effect of fracture prevention. [ABSTRACT FROM AUTHOR]

Continuous carbon fiber reinforced (SiC-ZrC) n multi-layer structural matrix composites were prepared by isothermal chemical vapor infiltration method. The microstructure, bending and ablation behavior of the composites with different number (n, n = 1, 2, 4) of SiC-ZrC layer were studied. The fracture morphology was step-like fracture. With the increase of n, the number of interfaces doubled, benefiting that the cracks kept deflecting and branching at the interface to consume lots of energy. The bending strength increased from 127.63 MPa (n = 1) to 276.85 MPa (n = 4). After ablation, among the prepared composites, C/(SiC-ZrC) 4 composite not only had the highest residual bending strength (169 MPa), but also had the best ablation resistance, which the mass and linear ablation rates were 1.17 ± 0.19 mg/s and 7.50 ± 0.56 µm/s, respectively. [ABSTRACT FROM AUTHOR]

A TiAl-based alloy, Ti–45Al–2Cr–5Nb (at.%), has been processed by selective laser melting (SLM) using different energy density inputs. The experimental results show that when the energy density input increased from 250 J/mm 3 to 350 J/mm 3 , the crystallographic texture varied from a strong (0001) orientation to a combination of (0001), 10 1 ̅ 1 and 11 2 ̅ 1 orientations. The SLM-processed TiAl alloy are dominated by high-angle (> 15°) grain boundaries (HAGBs) and α 2 (Ti 3 Al) phase. The contents of HAGBs and α 2 are 92.8% and 90% respectively at the maximum density input of 350 J/mm 3 . Moreover, a small amount of γ (TiAl) and B 2 phases in a range of several hundred nanometers are uniformly distributed within the α 2 matrix. The phase evolution mechanism in the SLM-processed TiAl alloy can be as follows: (210) β transformed to 20 2 ̅ 0 α 2 and (110) γ, and then the residual B 2 and the incompletely transformed γ phase homogeneously distributed in the α 2 phase matrix. The orientation relationship between B 2 , α 2 and γ phases observed via HRTEM can be expressed as: 111 B 2 / / 1 1 ̅ 0 γ / / 11 2 ̅ 0 α 2 . Those observations and discussions provide a deep insight into the microstructure characteristics and phase evolution in the SLM-processed TiAl alloy, and the findings would be a valuable reference for optimizing the energy density input in SLM to fabricate TiAl components with acceptable grain structure and phase compositions. [ABSTRACT FROM AUTHOR]

The titanium alloy Ti–6Al–4V (TC4) and tungsten (W) possess excellent complementary properties that would be useful for a wide range of industrial applications if they could be suitably combined. Selective laser melting was applied to prepare TC4/W specimens with a bimetallic structure. A strong bond without interfacial macrocracks was obtained by adjusting the laser line energy density to <0.75 J/mm. The bond interface of the bimetallic structure reached a microhardness of 503 ± 20 HV, which was harder than that of the two base materials, and the transverse and longitudinal ultimate compressive strengths were 1510 ± 40 MPa at strains of 20%–22.5%. Three-point bending experiments showed that when TC4 was used as the base material, the flexural strength of the specimen was 2210.5 ± 44.5 MPa. The high strength of the bond interface was attributed to sufficient agitation of the molten pool and reinforcement by fine crystalline grains. The agitation was provided by the melting and elemental diffusion of TC4 owing to the high energy input during the formation of W, and the fine crystalline grains were obtained by the dispersed W particles providing multiple nucleation sites for liquid TC4. The bimetallic structure retained the strength of W and toughness of TC4, which bodes well for its industrial application. • Forming parameters affected bond strength of TC4/W bimetallic structure. • The forming of tungsten produced numerous fine β-phases at the bonded interface. • The microhardness of the interface of the TC4/W bimetallic structure reaches 503 HV. [ABSTRACT FROM AUTHOR]

The slurry and sol‐gel methods were used to introduce SiC nanowires (SiCnws) into the SiCf/HfC‐SiC composites. The microstructures, ablation, and bending behaviors of the SiCnws modified composites prepared by the two methods were compared. The bending strengths of the modified composites obtained by introducing SiCnws by the slurry and sol‐gel methods were 224 ± 19 and 154 ± 14 MPa, respectively. The results showed that SiC fibers with chemical corrosion and thermal damage during the sol‐gel process decreased the bending strength of the SiCnws‐modified SiCf/HfC‐SiC composites. Meanwhile, the pyrolytic carbon interface accompanying corrosion damage in the sol‐gel process led to the degradation of interface function, which hindered the interface debonding and fiber sliding of the composites during the bending test. After ablation, the bending strengths of the two composites were 188 ± 19 and 50 ± 7 MPa, respectively. The bending strength retention of the modified composites fabricated by the slurry method (83.9%) was higher than that (32.5%) of the composites fabricated by the sol‐gel method after ablation. As the composites fabricated by the slurry method exhibited a good ablation resistance under the oxyacetylene flame (∼2350°C). [ABSTRACT FROM AUTHOR]

[Display omitted] • Graphene disperses well in aromatic petroleum resin by solution mixing. • Dispersibility of graphene in aromatic resin improved with xylene content decreased. • Graphene slows down the swelling ratio of aromatic resin immersed in water. • Graphene in aromatic petroleum resin can effectively shield corrosion factors. Graphene (Gr) uniformly dispersed aromatic petroleum resin (APR) coatings were prepared using exfoliated Gr and APR as raw materials by solution mixing method. Graphene was first mixed with the xylene solution and treated by ultrasonication. Then the APR was added to the mixture solution, after heating and stirring to remove the excess xylene solvent, the APR solution with uniform dispersion of graphene could be obtained. Atomic force microscopy (AFM) was used to test the thickness variation of the multilayer graphene layers before and after xylene adsorption. The results showed that the xylene which increased the thickness of the multilayer graphene was interspersed between the graphene layers. Raman spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) characterized that graphene obtained a good dispersion of Gr in APR. The electrochemical characteristics of graphene-modified APR coatings were tested by electrochemical impedance spectroscopy (EIS), and the results showed that the xylene content influenced the dispersion of graphene and flowability of the APR solution. The Gr/APR coatings with 45 wt% xylene exhibited the best corrosion protection performance. The impedance modulus of the coating in the low-frequency region after being immersed in 3.5 wt% sodium chloride solution for 100 days was greater than 109Ω·cm2. [ABSTRACT FROM AUTHOR]

In this study, Cu–Sn-based diamond composites were fabricated using L-PBF. The effects of the Cu-coated diamond on the melt-pool evolution, diamond–metal matrix bonding, thermal damage, and friction behavior of Cu in the Cu–Sn-based diamond composites were investigated. Moreover, the optimum L-PBF parameters for processing Cu-coated diamond/Cu–Sn composites were investigated. A convolutional neural network based on deep learning was used to process laser-scanned diamond images and evaluate the diamond thermal damage by model-feature visualization. The thermally damaged Cu-coated diamond and percentage of severely damaged parts were reduced compared to those of the uncoated diamond. Thick Cu coating changed the wettability of the diamond and matrix, thereby increasing the friction of the molten pool and unmelted metal particles and introducing the friction of the Cu microfluidic flow on the diamond. Hence, the mechanical holding force of the Cu Sn alloy matrix on the diamond substantially increased, and the bending strength of the Cu-coated diamond/Cu–Sn composites fabricated using L-PBF reached 720 MPa, which is approximately twice that of diamond/Cu–Sn (365 MPa). • Cu-coated diamond/Cu-Sn composite was formed by laser powder bed fusion. • The bending strength of Cu-coated diamond/Cu-Sn composites reached 720 MPa. • The thick Cu coatings improved the mechanical holding force on the diamond. • Laser-scanned-diamond prongs were susceptible to thermal damage. [ABSTRACT FROM AUTHOR]

• SiC f /HfC-SiC and SiC nws modified SiC f /HfC-SiC composites were prepared by PIP and CVI methods. • SiC nws were helpful to increase the pyrolysis yield rate of HfC precursor. • After impact-ablation, the flexural strength of SiC f /HfC-SiC reduced by 45.2 %; that of modified one only reduced by 30.9 %. SiC nanowires (SiC nws) modified SiC f /HfC-SiC composites were prepared by precursor infiltration and pyrolysis (PIP) and chemical vapor infiltration (CVI) methods. The microstructure, flexural strengths, impact and impact-ablation tests of the composites with and without SiC nws were investigated. The results showed that after introducing SiC nws , not only the retention rate of HfC ceramic produced by PIP was increased obviously, but also the fracture displacement of the modified composites was reduced due to the enhancement effect of SiC nws at interface between SiC fiber and matrix. After impact and impact-ablation, the strength retention of SiC nws modified composites was 91.6 % and 69.1 % respectively, higher than that of the composites without SiC nws (85.2 % and 54.8 %). As the impact resistance of the modified composites was improved by the pull-out and bridging of SiC nws , the ablation resistance of the impacted composites was enhanced as well. [ABSTRACT FROM AUTHOR]

To improve the reliability of C f /HfC-SiC composites after ablation, SiC fibers were used as reinforcement to replace carbon fibers. The composites were prepared by precursor infiltration and pyrolysis (PIP) and chemical vapor deposition (CVD) methods. The flexural properties of the cyclic ablated C f /HfC-SiC and SiC f /HfC-SiC composites were characterized. The results showed that the flexural strengths of C f /HfC-SiC and SiC f /HfC-SiC composites before ablation were 98.3 ± 6.8 and 108.5 ± 1.9 MPa, respectively. After three cycles of ablation, the flexural strengths of C f /HfC-SiC composites were 37.2 ± 2.4 MPa (decreased by about 62.2%), and the bending strengths of SiC f /HfC-SiC composites were 79.6 ± 4.3 MPa (only decreased by 26.6%). The high retention rate of the bending strength of SiC f /HfC-SiC composites was due to the protection of the complete oxide layer and good oxidation resistance of the SiC fiber. [ABSTRACT FROM AUTHOR]

A composite coating was developed to address the issues of low binding force and poor wear resistance of the hydroxyapatite coating on the surface of magnesium alloy. The composite coating, known as (C-HA) SiCnws coating, was prepared on the surface of AZ31 magnesium alloy using the carbonation-oxidation method of phenolic resin and electrophoretic deposition. The (C-HA) SiCnws coating is composed of a carbon coating as the middle layer, a hydroxyapatite coating as the surface layer, and SiC nanowires that connect the carbon layer and the HA coating. The morphology and infrared spectrum of the coating were characterized, and tests were conducted to evaluate the adhesion, wear performance, electrochemical properties, and corrosion resistance of the coating. The results demonstrate that the (C-HA) SiCnws coating is uniform and flat. The adhesion of the coating, as determined by tensile, is 3.51 ± 0.54 MPa, which is 88 % higher than that of the pure HA coating. Furthermore, the wear performance of the (C-HA) SiCnws coating is excellent, with a wear rate of only 0.96 × 10−3 mm3/(N·m), representing a reduction of 68.2 %. Additionally, the (C-HA) SiCnws coating demonstrates a favorable corrosion protection effect in both electrochemical polarization and corrosion tests. Overall, the prepared (C-HA) SiCnws coating exhibits significant enhancements in terms of adhesion, wear resistance, and corrosion resistance. • The SiCnws and HA particles are uniformly and organically bonded together. • The oxidation of the C coating leads to the extension of SiCnws within the coating. • Adhesion, wear resistance and corrosion resistance are greatly improved. [ABSTRACT FROM AUTHOR]

Purpose: In the implementation of large-size additive manufacturing (AM), the large printing area can be established by using the tiled and fixed multiple printing heads or the single dynamic printing head moving in the x–y plane, which requires a layer decomposition after the mesh slicing to generate segmented infill areas. The data processing flow of these schemes is redundant and inefficient to some extent, especially for the processing of complex stereolithograph (STL) models. It is of great importance in improving the overall efficiency of large-size AM technics software by simplifying the redundant steps. This paper aims to address these issues. Design/methodology/approach: In this paper, a method of directly generating segmented layered infill areas is proposed for AM. Initially, a vertices–mesh hybrid representation of STL models is constructed based on a divide-and-conquer strategy. Then, a trimming–mapping procedure is performed on sliced contours acquired from partial surfaces. Finally, to link trimmed open contours and inside-signal square corners as segmented infill areas, a region-based open contour closing algorithm is carried out in virtue of the developed data structures. Findings: In virtue of the proposed approach, the segmented layered infill areas can be directly generated from STL models. Experimental results indicate that the approach brings us the good property of efficiency, especially for complex STL models. Practical implications: The proposed approach can generate segmented layered infill areas efficiently in some cases. Originality/value: The region-based layered infill area generation approach discussed here will be a supplement to current data process technologies in large-size AM, which is very suitable for parallel processing and enables us to improve the efficiency of large-size AM technics software. [ABSTRACT FROM AUTHOR]

• C f /HfC and C f @PyC/HfC composites were prepared at low temperature by precursor infiltration and pyrolysis and chemical vapor deposition method. • The results of thermal cyclic ablation and three-point bending tests show that after three time ablation cycles, the flexural strength of C f /HfC samples reduced by 63%; the flexural strength of C f @PyC/HfC samples only reduced by 36%. • The differences of cyclic ablation behaviour and flexural strength of C f /HfC and C f @PyC/HfC are attributed to the crucial function of PyC interface phase including protection of fiber and weakening of fiber/matrix interface. Composites based on hafnium carbide and reinforced with continuous naked carbon fiber with and without PyC interface were prepared at low temperature by precursor infiltration and pyrolysis and chemical vapor deposition method. The microstructure, mechanical property, cyclic ablation and fiber bundle push-in tests of the composites were investigated. The results show that after three times ablation cycles, the bending strength of samples without PyC interface decreased by 63.6 %; the bending strength of samples with PyC interface only decreased by 37.8 %. The force displacement curve of the samples with PyC interface presented a well pseudoplastic deformation state. The mechanical behavior difference of two kinds of composites was due to crucial function of PyC interface phase including protection of fiber and weakening of fiber/matrix interface. [ABSTRACT FROM AUTHOR]

Metal bond diamond abrasive tools with complex structure and high wear efficiency will be widely used in the geological drilling and mechanical processing industries, but are difficult to manufacture by traditional technology. In this paper, selective laser melting (SLM), as one of the additive manufacturing technologies, was used to fabricate Cu-Sn-Ti bonded diamond abrasive composites. Simulations, experiments and characterization were carried out to obtain the appropriate SLM process parameters. Results indicated that the optimal SLM parameters were laser power of 260 W, scanning speed of 300 mm/s and layer thickness of 0.09 mm. Furthermore, the wear resistant performance of SLM sample was compared with hot-pressed sintered sample in terms of mass loss rate, wear morphology and bonding condition. Results showed that diamond particles were seriously pulled-out from hot-pressed sintered sample while this hardly occurred from the wear surface of SLM sample, which was benefited from higher amounts of TiC around the diamond. Consequently, the bonding force to diamond was effectively improved for SLM sample. Therefore, SLM method cannot only fabricated sample with complex structures, but also with better performance. This study provides a novel approach for forming metal bonded diamond tools by SLM in the future. • Cu-Sn-Ti alloys melted while diamond particles did not with power of 100–300 W. • SLM sample had the best mechanical property by 260 W and 300 mm/s. • SLM sample achieved the better bonding force to diamond and wear resistance. [ABSTRACT FROM AUTHOR]

Integrated sensor–actuators with exciting functionalities, such as action self‐sensing, position self‐sensing, posture self‐sensing, or active sensing, are promising for applications in biomedical device, human–machine interaction, intelligent self‐protection devices, and humanoid robots. Despite recent progress, it remains challenging to achieve a macroscopical integrated sensor–actuator in a material system with microstructures. To address this critical challenge, a 4D printing bioinspired microstructure strategy is reported to design a high‐performance integrated sensor–actuator capable of simultaneous actuation and sensation. Decoupled thermal stimulation and strain sensation is achieved by combining nanocarbon black/polylactic acid composites with bioinspired gradient microgap structures. As a result, printed integrated sensor–actuators can actively touch objects triggered by thermal stimulation and self‐sense the touching state through the resistance change. It is anticipated that the basic design principle underlying this behavior can be used to develop integrated sensor–actuators of various shapes and functionalities to meet desirable applications. [ABSTRACT FROM AUTHOR]

Triply Periodic Minimal Surface (TPMS) porous structures are recognized as the most promising bionic artificial structures for tissue engineering. The fatigue properties of additive manufactured porous structures are essential for long-term use in a dynamical bio-skeletal environment. The aim of this study is to study the compression–compression fatigue behaviour and the underlying fatigue mechanism of Gyroid cellular structures (GCS), a typical TPMS porous structure. The high-cycle fatigue results show that both cyclic ratcheting and fatigue damage phenomena contribute to the failure of GCS during fatigue testing. For most fatigue loading stress, the failure samples have nearly 45° fracture bands along the diagonal surface. The fatigue ratio of GCS reaches 0.35 for as-built samples and can be raised to 0.45 after sandblasting treatment. The fatigue ratio values are higher than most of the other bending-dominated lattice structures, suggesting superior fatigue resistance properties of GCSs due to the smooth surface connection between struts. Besides, a systematic investigation of the crack initiation and propagation was conducted by both deformation analysis and finite element method to support experimental phenomena. The results also indicate that the fatigue resistance properties of GCSs are significantly enhanced by sandblasting post-treatment, through removing the adhered powder particles, inducing compressive residual stress on the surface and generating a nanocrystalline zone. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA) coatings doped with different contents of SiC nanowire (SiCnws) were prepared on the surface of AZ31 magnesium alloy by electrophoretic deposition to solve the problems of low adhesion and poor wear resistance of pure HA coatings. Performance tests were conducted on the coating, including corrosion resistance, adhesion and wear performance. The results showed that the prepared coating was intact. The adhesion and wear resistance of the coating were significantly improved when the doping amount of SiCnws was 3%. Among them, the adhesion increased by 37.06% and the scratch depth decreased by 86.67%. At the same time, the corrosion resistance of the coating still maintained a high level. It showed that the performance of doping 3% SiCnws modified coating was balanced and excellent in all aspects. [Display omitted] • HA-SiCnws composite coating is prepared on AZ31 magnesium alloy. • The SiCnws and HA particles are uniformly and organically bonded together. • Adhesion and wear resistance are greatly improved. [ABSTRACT FROM AUTHOR]

Abstract The Cu-13.5Al-4Ni-0.5Ti copper-based shape memory alloys (SMAs) were fabricated by selective laser melting (SLM). The parameters were optimized to obtain almost fully dense copper-based SMAs samples. The phases and microstructures were characterized and the tensile properties at room temperature and 200 °C were evaluated. The XRD results showed that only the β 1 ′ phase could be detected in the Cu-based SMAs, which was attributed to the extremely short solidification time for the precipitation of α and γ 2 phases during SLM process. The grains were well refined and the average grain size was approximate 43 μm, which was much smaller than that of the cast copper-based SMAs. The X-phase (Cu 2 TiAl) is observed, which is granular and size 20–50 nm. The Cu-13.5Al-4Ni-0.5Ti copper-based SMAs fabricated by SLM exhibited excellent mechanical properties at room temperature, which was higher than that of the cast copper-based SMAs. This is attributed to two aspects: (1) grain refinement, (2) suppress of brittle γ 2 phase. Remarkably, the tensile test results at 200 °C showed both higher strength and elongation, which is attributed to the bcc structure of the parent phase and the stress-induced martensitic transformation at 200 °C. Meanwhile, the difference of microstructures and properties between SLM-fabricated Cu-based SMAs and casting Cu-based SMAs were analyzed and discussed in detail. Graphical abstract Image 1 Highlights • Near fully density Cu-13.5Al-4Ni-0.5Ti SMA is successfully fabricated. • β 1 ′ martensite and X phases are emerged in SLM-fabricated Cu-13.5Al-4Ni-0.5Ti. • The grain size of Cu-13.5Al-4Ni-0.5Ti alloy is smaller than cast counterparts. • The SLM-fabricated Cu-13.5Al-4Ni-0.5Ti SMA shows superior mechanical properties. [ABSTRACT FROM AUTHOR]

Background: Diffusion tensor imaging (DTI) provides information about water molecule diffusion in spinal cord.Purpose: This study was aimed to investigate DTI changes in the different stages of compressive spinal cord induced by water-absorbing material implantation.Material and Methods: The spinal cord compression was administered over the fourth cervical vertebral level in rat. Rat models were divided into five subgroups according to compression stages: sham group, group A: three-day compression rat models; group B: 12-day compression rat models; group C: 20-day compression rat models; group D: 60-day compression rat models. DTI including fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in the compressive spinal cord were collected. The relationship between the Basso, Beattie, and Bresnahan (BBB) scores and DTI metrics was further explored.Results: Compared with the sham group, BBB scoring of rat model showed a decreased tendency from group A ( P < 0.05) to group B ( P < 0.05). Then the motor function of rat model hindlimbs was recovered in some degree from group C ( P < 0.05) to group D ( P < 0.05) but had significant motor defects when compared with the normal level ( P < 0.05). The DTI metrics results revealed that chronic spinal cord compression resulted in lower FA value and higher ADC value at the compressive spinal cord level assessed at all four time-points ( P < 0.05). DTI metrics also showed a close correlation with motor function ( P < 0.05).Conclusion: DTI is an optimal pre-clinical imaging tool to reflect locomotor performance and pathological status of compressive spinal cord epicenter in chronic spinal cord compression rat model. [ABSTRACT FROM AUTHOR]

Abstract In this study, a new hot-isostatic-pressing process was proposed, combining with the thermo-hydrogen-treatment process. Effects of hydrogen-atoms on the surface-oxide-film and the compaction-temperature of Ti-47Al-2Cr-2Nb pre-alloyed powders were investigated during hot-isostatic-pressing. Results show that the surface-oxide-film of powders of thermo-hydrogen-treatment can be effectively removed. For samples prepared by the new hot-isostatic-pressing process, the oxygen content decreased by 130 ppm and the compaction-temperature reduced by 50–100 °C, comparing with samples prepared by the traditional hot-isostatic-pressing process. After high-temperature vacuum annealing, the compressive fracture strength and ratio of samples prepared by the new hot-isostatic-pressing process is as high as 2830 MPa and 34.5%. Highlights • Hydrogen-atoms were removed in two steps during hot isostatic pressing. • Surface oxide film of powders can be removed by hydrogen-atoms. • Oxygen content of parts decreases by 130 ppm. • Compaction temperature of hot isostatic pressing reduces by 50–100 °C. [ABSTRACT FROM AUTHOR]

Abstract Selective Laser Sintering (SLS) is one of the most mature and engineered polymeric 3D printing technologies, and the produced part is characterized by homogeneous polymorphism, which make the sintered material possess an ordered crystalline phase distribution and thus present a self-formed composite structure. This is due in large part to the special processing method during the SLS process. However, molecular motion mechanism between different phases remain unclear and further exploration is needed. Therefore, this paper firstly investigates the molecular motion mechanism concerning special composite phase structure of SLS-processed PA6 based on 2D correlation fourier transform mid-infrared (FT-MIR) spectra. The results show that although the crystal structure of the LT-α phase is less-ordered, the groups in LT-α change later than those in HT-α as the temperature increases. The overall movement sequence is: HT-α ˃ interphase ˃ LT-α, and the motion mode in the individual phase is the skeleton movement of carbon chains driven by H-bonds whereas the movement of interphase H-bonds is driven by the synergistic effect of the chain in HT-α. Besides, the symmetric methylene (v s (CH 2)) vibrates firstly both for HT-α and LT-α, and then is the stretching vibration of asymmetric methylene (v a s (CH 2)). Graphical abstract Image 104391 Highlights • This paper firstly investigates the composite phase structure of 3D-printed PA6 based on 2D correlation FT-MIR spectra. • The assignments of laser sintered PA6 concerning HT-α, interphase and LT-α were firstly presented. • The H-bonds in the interphase are mainly linked to the carbon skeletal chain of HT-α spherulites rather than LT-α. • The overall movement sequence of molecular chain is: HT-α ˃ interphase ˃ LT-α. • The v s (CH 2) vibrates firstly both for HT-α and LT-α, and then is the stretching vibration of v a s (CH 2). [ABSTRACT FROM AUTHOR]

Abstract In this study, the in-situ synthesized TiB/Ti-6Al-4Vceramic-matrix nanocomposites with greatly enhanced hardness and wear resistant property have been prepared via selective laser melting (SLM) using a simple mixture of microsized Ti-6Al-4V and TiB 2 powders. In order to provide a valuable reference for fabricating TiB/Ti-6Al-4V parts with metallographic features, effects of reinforcement content on microstructure and mechanical properties have been systematically investigated. It is found that during SLM process, the additive particles TiB 2 are totally transformed into need-like nanoscaled TiB phase, and the microstructure of composites is composed of mutual parallel strips architecture with TiB rich in some regions but lean in the other regions. The SLM-producedTiB/Ti-6Al-4 V composites exhibit superior nanohardness of 6.0 GPa, which is much higher than its traditional sintering counterpart. Moreover, the in-site synthesized TiB reinforcement can remarkably improve in the wear resistance properties, the wear loss of TiB-free sample is approximately 2 times than that of the sample with 3 wt% TiB 2. Graphical abstract Unlabelled Image Highlights • In-situ synthesized TiB/Ti-6Al-4V nanocomposites have been prepared via SLM. • The need-like nanoscaled TiB phase formation and evolution mechanism during SLM is discussed in detail. • The interface orientation relationship between TiB and Ti matrix has been investigated. • The SLM-producedTiB/Ti-6Al-4V composites exhibit superior hardness and outstanding wear resistant property. [ABSTRACT FROM AUTHOR]