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Nickel-based self-lubricating cladding containing Ag and MoS2was prepared on Ti6Al4V alloy using laser cladding. The microstructure, microhardness and wear behaviour were measured and analysed. The coating was mainly composed of Ti2Ni and TiNi as the matrix, and TiC and TiB2as the reinforcements. A new phase of Ti2SC was synthesized in situ in the coating, whereas Mo was consolidated in the matrix. The microhardness of the coating is greatly increased by in-situ generation of reinforcement phase and solution strengthening, with an average hardness of 823.6HV0.2, which is about 2–3 times that of the substrate. When the temperature increased to 600 °C, the coefficient of friction and wear rate of the coating decreased. The friction coefficient and the wear rate of the coating were greatly reduced at 800 °C. The wear rate of the coating decreased to 4.85 × 10−6 mm3, which decreased by nearly an order of magnitude compared with the coating's wear rate at room temperature. The anti-friction effect of the lubricating phase not only counteracted the effect of the decreased hardness on the wear rate, but also played a more obvious anti-friction effect. In the high-temperature stage, MoO3and silver molybdate compounds produced by the tribological chemical reaction of wear surfaces could significantly improve the density of the enamel layer on the wear surface.

This study aims to accurately predict the nonlinear characteristics of transmission efficiency of cycloid reducers under different operating conditions. Firstly, equivalent modeling of the multi-source errors (MSEs) in the designed cycloid reducer is conducted. Force analysis algorithms considering MSEs are proposed for the cycloid drive mechanism, the output mechanism, and the bearings. Secondly, mathematical models are established for the load-dependent power losses, while an equivalent test is used for modeling load-independent power losses. Subsequently, an improved transmission efficiency prediction (TEP) method for cycloid reducers is proposed, which is then applied to the performance prediction of a prototype under different operating conditions. The advantages of the improved TEP method over the conventional method are discussed, and the influences of MSEs and load-independent power losses on the nonlinear characteristics of transmission efficiency are summarized. Finally, tests are conducted for the reducer prototype, and the test results are found to be in good agreement with the results obtained by the proposed TEP method. The main contribution of this study is to establish a solid algorithmic and modeling foundation for the optimal design of nonlinear transmission efficiency in cycloid reducers and provide reliable guidance for their engineering applications.

In this contribution, we reported the crosslinking of polyethylene (PE) with dynamic silyl ether bonds. First, polycyclooctene copolymers bearing hydroxyl groups were synthesized via the ring‐opening metathesis copolymerization of cyclooctene with 5‐norbornene‐2‐methanol. The hydroxy‐functionalized polycyclooctene copolymers were further hydrogenated into the corresponding hydroxy‐functionalized PE copolymers. The PE copolymers were allowed to react with 3‐isocyanatopropyltriethoxysilane to obtain the PE copolymers bearing triethoxysilane groups. By taking advantage of hydrolysis and condensation of triethoxysilane groups grafted onto PE chains, the PE copolymers were well crosslinked; polysilsesquioxane (PSSQ) segments behaved as the crosslinking linkages in the networks. Notably, the PE networks were reprocessable (or recyclable) while zinc trifluoromethanesulfonate [Zn(OTf)2] was incorporated. The reprocessing properties of the PE networks were quite dependent on the crosslinking densities. The reprocessing behavior of the networks is attributable to the introduction of two dynamic chemistries: (i) the metathesis of silyl ether bonds which was catalyzed with Zn(OTf)2and (ii) transcarbamoylation of carbamates which was catalyzed with dibutyltin dilaurate. Owing to the crosslinking, the PE networks displayed excellent shape memory properties. For the shape memory networks, notably, the original shapes can be reprogrammed with the aid of the exchange of the dynamic covalent bonds introduced into the systems.

Polyhedral oligomeric silsesquioxanes (POSS) are a class of well‐defined organic–inorganic stereo molecules comprising inorganic SiOSi cores and peripheral organic moieties. Since they were first reported in 1946 by Scott et al., there have been a great number of investigations on the use of POSS macromers as the building blocks to access the organic–inorganic composites with polymers. In most of cases, monofunctional POSS macromers are employed and the linear hybrid polymers are obtained. Under this circumstance, POSS cages act as the side or end groups whereas the main chains of the polymers remain unchanged. Occasionally, octafunctional POSS macromers are involved, resulting in the generation of crosslinked (or network‐like) hybrids. Recently, well‐defined difunctional POSS macromers have increasingly provoked a considerable attention of investigators. From the synthetic methodology of POSS macromers to the approaches to introduce them into polymers, difunctional POSS macromers have the features quite different from mono‐ (or octa‐) functional POSS. More importantly, the related organic–inorganic hybrids possess the different morphologies and properties. In the past years, there has been a rapid increase in the number of literatures on the studies on well‐defined difunctional POSS and the related organic–inorganic hybrids. Nonetheless, the related review is lacking. In this contribution, we would summarize the recent progress in this regard, from the synthesis of POSS macromers, the approaches of introducing the POSS macromers into polymers to the correlation of morphologies with properties of the organic–inorganic hybrids. In addition, perspectives and challenges for the further advancement are envisaged and discussed.

In this study, we used the recently developed ultrasound elastography techniques sound touch elastography (STE) and sound touch quantification (STQ) to quantify portal hypertension (PHT) severity in a rat model of carbon tetrachloride (CCl4)‐induced cirrhotic PHT. In total, 60 rats were used. Various degrees of PHT were established. Liver and spleen stiffness were measured by STE (L‐STE and S‐STE, respectively) and STQ (L‐STQ and S‐STQ, respectively). We measured portal pressure (PP) after ultrasonographic examination. The performance of the STE and STQ parameters in the identification of PHT was evaluated using receiver operating characteristic (ROC) analyses. Liver and spleen stiffness measurements obtained with STE and STQ correlated positively with the PP (r= 0.566–0.882, all P< .001). The areas under ROC curves for L‐STE, S‐STE, L‐STQ, and S‐STQ values were 0.931 (95% confidence interval [CI], 0.847–1.000), 0.982 (95% CI, 0.956–1.000), 0.796 (95% CI, 0.680–0.912), and 0.925 (95% CI, 0.858–0.993), respectively, for PP ≥5 mmHg; 0.937 (95% CI, 0.865–1.000), 0.938 (95% CI, 0.864–1.000), 0.967 (95% CI, 0.923–1.000), and 0.960 (95% CI, 0.897–1.000), respectively, for PP ≥10 mmHg; and 0.954 (95% CI, 0.897–1.000), 0.790 (95% CI, 0.652–0.928), 0.808 (95% CI, 0.680–0.935), and 0.740 (95% CI, 0.595–0.885), respectively, for PP ≥12 mmHg. STE and STQ are reliable noninvasive tools for the assessment of PHT severity, especially for PP ≥10 mmHg, in a rat model of CCl4‐induced cirrhotic PHT.

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Inhibition of vascular endothelial growth factor receptor (VEGFR) has shown antitumour activity in advanced hepatocellular carcinoma, but few studies of VEGFR inhibitors have been done in populations with a high prevalence of hepatitis B virus infection. The aim of this study was to evaluate the efficacy and safety of apatinib in patients with pretreated advanced hepatocellular carcinoma.

ABSTRACTIn situ synthesized TiN and TiB reinforced metal matrix composite coating was fabricated on Ti-55511 by laser cladding with Ti-55511/BN powder mixture (2 wt-% BN). Results indicated that coating was mainly composed of TiB, dendrite TiN and α phase. The diameter of small-sized hollow tubular TiB was less than 400 nm, and the width of the other rod-shaped TiB was less than 1 μm. The flower-like structure formed during solidification consisted of TiN dendrite in centre and rod-shaped or hollow tubular TiB at edge. Coating had high hardness (540 HV) due to formation of TiB and TiN. After direct aging (600°C/5 h/AC), the hardness of coating and HAZ increased to 660 and 450 HV respectively because of nano-scaled α phase precipitation. In the friction and wear test, the weight loss of the coating was only 62% of that of substrate, which further reduced to 47% after aging.

In situ synthesized TiN and TiB reinforced metal matrix composite coating was fabricated on Ti-55511 by laser cladding with Ti-55511/BN powder mixture (2 wt-% BN). Results indicated that coating was mainly composed of TiB, dendrite TiN and a phase. The diameter of small-sized hollow tubular TiB was less than 400 nm, and the width of the other rod-shaped TiB was less than 1 µm. The flower-like structure formed during solidification consisted of TiN dendrite in centre and rod-shaped or hollow tubular TiB at edge. Coating had high hardness (540 HV) due to formation of TiB and TiN. After direct aging (600°C/5 h/AC), the hardness of coating and HAZ increased to 660 and 450 HV respectively because of nano-scaled a phase precipitation. In the friction and wear test, the weight loss of the coating was only 62% of that of substrate, which further reduced to 47% after aging.

ABSTRACTSupersaturated carbon alloying layer was prepared on the surface of 15-5PH stainless steel using laser surface alloying technology with carbon powders as alloying materials. XRD, optical microscope, scanning electron microscope, microhardness test and wear test were performed to characterize the microstructure and wear resistance of substrate and alloying layer. Results showed that the alloying layer was rapidly solidified dendritic structure with phase compositions of high-carbon austenite and a small amount of martensite and M7C3carbides. Microhardness of the alloying layer reached about 510 HV, which was 38.7% higher than that of the as-deposited substrate (375 HV). Carbon supersaturated solid solution strengthening and microstructure refinement strengthening were the main reasons for a substantial increase in alloying layer microhardness. After direct aging treatment, microhardness of the alloying layer further increased to nearly 640 HV. Wear test results showed that the mass loss of the aging alloying layer was about 60% lower than that of the aging substrate, which meant significantly improvement of wear resistance.

Supersaturated carbon alloying layer was prepared on the surface of 15-5PH stainless steel using laser surface alloying technology with carbon powders as alloying materials. XRD, optical microscope, scanning electron microscope, microhardness test and wear test were performed to characterize the microstructure and wear resistance of substrate and alloying layer. Results showed that the alloying layer was rapidly solidified dendritic structure with phase compositions of high-carbon austenite and a small amount of martensite and M7C3carbides. Microhardness of the alloying layer reached about 510 HV, which was 38.7% higher than that of the as-deposited substrate (375 HV). Carbon supersaturated solid solution strengthening and microstructure refinement strengthening were the main reasons for a substantial increase in alloying layer microhardness. After direct aging treatment, microhardness of the alloying layer further increased to nearly 640 HV. Wear test results showed that the mass loss of the aging alloying layer was about 60% lower than that of the aging substrate, which meant significantly improvement of wear resistance.

ABSTRACTThe primary understanding of laser-induced non-isothermal prior βgrain growth behaviour of titanium alloys is given by adopting laser quenching on pure titanium. Results indicate that the prior βgrains grow obviously within the limited laser interaction time. By establishing a finite element model combined with numerical approximations, the growth activation energy of prior βgrain under laser-induced non-isothermal condition is determined as 44.4 kJ/mol, which is comparable to that under isothermal conditions. Grain boundary migration behaviour of pure titanium under laser-induced non-isothermal conditions is the same as that under isothermal conditions, but the prior βgrain growth kinetics is largely accelerated due to the high heat input from the laser beam.

The primary understanding of laser-induced non-isothermal prior ßgrain growth behaviour of titanium alloys is given by adopting laser quenching on pure titanium. Results indicate that the prior ßgrains grow obviously within the limited laser interaction time. By establishing a finite element model combined with numerical approximations, the growth activation energy of prior ßgrain under laser-induced non-isothermal condition is determined as 44.4?kJ/mol, which is comparable to that under isothermal conditions. Grain boundary migration behaviour of pure titanium under laser-induced non-isothermal conditions is the same as that under isothermal conditions, but the prior ßgrain growth kinetics is largely accelerated due to the high heat input from the laser beam.

This study investigated the sources of stress, corresponding symptoms, and stress relief among nurses of the first Chinese anti-Ebola medical team during the Sierra Leone aid mission.

Abstract In this study, the crack propagation behaviors in the equiaxed and equiaxed-columnar grain regions of a heat-treated laser additive manufacturing (LAM) TC11 alloy with a special bi-modal microstructure are investigated. The results indicate that the alloy presents a special bi-modal microstructure that comprises a fork-like primary α (α p) phase surrounded by a secondary α colony (α s) in the β phase matrix after the heat treatment is completed. The samples demonstrate a fast crack growth rate with larger d a /d N values through the equiaxed grain sample versus across the equiaxed-columnar grain sample at low Δ K values (<13.8). The differences that are observed between the crack propagation behaviors (in the crack initiation stage) of the samples can be mostly attributed to the different size and morphology of the α p lamellae and α s colony within the grains in the equiaxed and columnar grain regions rather than the grain boundaries. The cracks prefer to grow along the α/β boundary with a smooth propagation route and a fast propagation rate in the equiaxed grain region, where the α p and α clusters have a large size. However, in the columnar grain region, small and randomly distributed α p lamellae generate a zigzag-shaped propagation path with a reduction in the d a /d N value. Additionally, the change in the size of the α p lamellae in the equiaxed grains (heat affected bands, HAB) is also observed to influence the propagation behavior of the crack during the crack initiation stage. [ABSTRACT FROM AUTHOR]

Micron-scale face-centered cubic titanium phase (named as δ phase) were noticed in the re-melted zone of laser surface re-melted commercially pure titanium plate. The morphology, sub-structure, orientation and distribution of δ phase were investigated by scanning electron microscopy, electron back-scattered diffraction and transmission electron microscopy. Three kind formation processes of δ phase were put forward based on the investigation. The first one is α′ → δ transformation which takes place in single α′ grains and leads to the orientation relationship {001}δ//{0001}α′ < 110 > δ / / < 11 2 ¯ 0 > α ′ . The second one is β → α′ + δ transformation which takes place at α′/α′ interfaces and leads to the orientation relationship {001}δ// { 1 1 ¯ 0 } β 〈110〉δ//〈111〉β. The third one is another kind of β → α′ + δ transformation that takes place at α′/α′ interfaces and leads to the orientation relationship { 1 1 ¯ 1 } δ// { 1 1 ¯ 0 } β < 110 > δ// < 111 < β. It is believed that the transformations of δ phase are stress assistant ones and in the present investigation, the phase transformation stress of β → α′ transformation acts as the assistant driving force for the formation of δ phase. [ABSTRACT FROM AUTHOR]

A layer of AerMet100 steel was coated on the surface of forged 300 M steel using laser cladding technique. The chemical compositions, microstructures, hardness and tensile properties of this AerMet100/300 M material were systematically investigated. Results show that the composition of the AerMet100 clad layer is macroscopically homogeneous, and a compositional transition zone with width of 150 μm is observed between the clad layer and heat affected zone. Microstructures in transition zone transform from the fine needle-like bainite in 300 M steel to the lath tempered martensite in AerMet100 clad layer. Microstructures in heat affected zone also gradually change from the thick plate bainite and blocky retained austenite (unstable heat affected zone) to fine needle-like bainite and film-like austenite (stable heat affected zone) due to different thermal cycle processes. Thick plate bainite together with blocky retained austenite in unstable heat affected zone reduce the strength and ductility of AerMet100/300 M material. However, the tensile specimens, consisting of clad layer and stable heat affected zone, show slightly inferior mechanical properties to 300 M steel. Ductile fracture exists in AerMet100 clad layer while quasi-cleavage fracture occurs in the stable heat affected zone. [ABSTRACT FROM AUTHOR]

Lightweight refractory high-entropy alloys (LRHEAs) exhibit lower density and better ductility than other refractory high-entropy alloys, which bestows upon them substantial prospects for application across diverse engineering domains. laser directed energy deposition additive manufacturing (LDED) technology emerges as an ideal process for preparing such refractory metals owing to its exceptional attributes, such as rapid cooling rates and design flexibility. In this study, a new LRHEA Al0.3NbTi3VZr1.5was fabricated by LDED, and a comprehensive investigation was conducted to explore the microstructure evolution and the plastic deformation mechanisms. A graded microstructure with body-centered cubic (BCC) matrix, Laves phases near grain boundaries, and coarsened ω particles in the matrix is detected in as-deposited samples. In solid solution treated (SST) samples, the Laves phase disappears, and the ω particles decrease in size, forming a nanoscale two-phase mixture with the matrix. The as-deposited samples exhibit distinct brittle fractures, with a fracture strength of 902 MPa and 1% fractured strain. While the SST samples exhibit a considerable fracture strain of about 25 ± 2% with 1032 ± 12 MPa yield strength and a specific yield strength of 180 MPa·g−1·cm3. The high strength is mainly attributed to the solid-solution strengthening, while the excellent ductility is achieved by activating the unique deformation mechanism, including the formation of multi-stage microbands and kinking. The refinement of microband spacing accommodates more plastic deformation, and cross-slip further refines the microbands spacing in three dimensions. Microband-induced kinking effectively relieves local stress concentration and slows fracture. This work provides new insights into the design and preparation of LRHEAs using additive manufacturing technology and makes a remarkable contribution to the comprehensive and in-depth understanding of their plastic deformation mechanisms.