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Additive manufacturing (AM) of Mg alloys has become a promising strategy for producing complex structures, but the corrosion performance of AM Mg components remains unexploited. In this study, wire and arc additive manufacturing (WAAM) was employed to produce single AZ31 layer. The results revealed that the WAAM AZ31 was characterized by significant grain refinement with non-textured crystallographic orientation, similar phase composition and stabilized corrosion performance comparing to the cast AZ31. These varied corrosion behaviors were principally ascribed to the size of grain, where cast AZ31 and WAAM AZ31 were featured by micro galvanic corrosion and intergranular corrosion, respectively.

Interface considerably influences the properties of copper (Cu)–graphite composites. Therefore, considerable understanding of the interface is required to improve the mechanical and tribological properties of these composites. Because the graphite (0001) and Cu (111) interfaces are a good match, this study focuses on calculating the related properties of the interface structure using first–principles calculations. The parameter setting of this work is reasonable when comparing the theoretical and experimental results of the bulk Cu and graphite. Slabs of the nine-layer graphite (0001) and seven-layer Cu (111) surfaces have excellent convergence. The order of interfacial configuration stability is [Formula: see text] and HCP possesses the largest work of adhesion and smallest interface energy among the studied interface structures. Furthermore, the electron density and Mulliken population method are used to examine the interfacial bonds.

Influenza hemagglutinin that drives viral entry into cells via the membrane fusion process is an up-and-coming antiviral drug target. Herein, we described for the first time the design, synthesis, and biological characteristics of a new class of pentacyclic triterpenoid-based proteolysis targeting chimeras (PROTACs) to enhance the degradation of hemagglutinin target. Among these PROTACs

To overcome the dimension limits of immiscible alloys produced by traditional techniques and enhance their mechanical properties, bulk Cu-Fe-based immiscible alloy with abundant nanotwins and stacking faults was successfully produced by selective laser melting (SLM). The SLM-produced bulk immiscible alloy displays a heterogeneous microstructure characterized by micro-scaled γ-Fe particles dispersed in fine e-Cu matrix with a high fraction (∼92%) of high-angle grain boundaries. Interestingly, abundant nanotwins and stacking faults are generated in the interior of nano-scaled γ-Fe particles embedded within e-Cu matrix. The heterogeneous interface of soft domains (e-Cu) and hard domains (γ-Fe) not only induces the geometrically necessary dislocations (GNDs) but also affects the dislocation propagation during plastic deformation. Therefore, the bimodal heterogeneous interface, and the resistance of nanotwins and stacking faults to the propagation of partial dislocation make the bulk immiscible alloy exhibit an enhanced strength of ∼590 MPa and a good ductility of ∼8.9%.

The microstructure of machined superficial layer significantly affects the mechanical properties and service life of mechanical components. Herein, to obtain a machined surface with excellent properties, a comprehensive application of theoretical calculations and test analysis research methods was conducted to investigate the influence mechanism of machining on performance and quality of machined superficial layer of high-strength alloy steel during machining, and reveal the intrinsic correlation between microstructure evolution, quality and performance of machined superficial layer. The results indicate that the machining can achieve gradient microstructure on the machined surface, which can improve the performance of machined surface greatly. From the surface to the inside region, the layers are respectively the recrystallized layer where compact nano-sized equiaxed grains are located, the rheological layer with clusters of high-density sub-grain structures, and the distorted layer with residual distorted grains. The maximum strain of superficial layer in the machined state is 2.81 times that of the original state. The grains are evidently refined and the grain size is reduced by 49.03%. The dislocation density is enhanced by 100.69%, while the number of small-angle grain boundaries (SAGB) and other substructures increase sharply, being 5.26 times that in the original state. By performance testing, the machining substantially enhances the hardness of the superficial layer of high-strength alloy steel with certain rise in toughness simultaneously, which is exactly the result of the combined effect of fine-grain strengthening and dislocation strengthening caused by the machining process above.

The anisotropic elastic, thermal properties and electronic structures of ternary layered transition metal borides M2AlB2 (where M = Fe, Cr, and Mn) were analysed using first-principles calculations and the Debye quasi-harmonic approximation. There was a good agreement between our calculated lattice constants and previous experimental and theoretical results. Our calculated thermodynamic stability parameters demonstrated that these borides had stable structures. Mn2AlB2 was the most incompressible material, while Cr2AlB2 was more rigid and a transversely resistant deformed material. The anisotropy of elasticity of the compounds was also estimated. They had different anisotropic elastic properties. The chemical bonding of the compounds primarily involved mixed covalent-metallic interactions. Covalent bonds were present between the boron and metal atoms. The M-M and B-B bond lengths were the longest and shortest in these compounds, respectively, and the bond strength in Fe2AlB2 was stronger. The anisotropic linear thermal expansion coefficients of these materials were also calculated. The thermal expansion in the [001] direction was the largest relative to the other two directions.

In this study, sulfated polysaccharides extracted from Laminaria japonica were degraded by free radicals to obtain low molecular weight fucoidan (LMWF). The in vivo and in vitro effects of LMWF on bleomycin-treated pulmonary fibrosis mice and TGF-treated A549 cells, respectively, were evaluated, and the role of antioxidant activity was assessed. H&E, Masson’s trichrome, and Sirius red staining results showed that bleomycin induced obvious pathological changes and collagen deposition in the lung tissue of mice. However, LMWF effectively inhibited collagen deposition, and based on immunohistochemistry analyses, LMWF can also inhibit the expression of fibrosis markers. At the same time, LMWF could regulate related antioxidant factors in the lung tissue of pulmonary fibrosis mice and reduce the pressure of oxidative stress. Moreover, LMWF could improve the morphology of cells induced with TGF, which confirmed that LMWF could inhibit fibrosis via antioxidant activity modulation.

In our continuing efforts toward the design of novel pentacyclic triterpene derivatives as potential anti-influenza virus entry inhibitors, a series of homogeneous heptavalent glycyrrhetinic acid derivatives based on

Two-body abrasive wear tests of Fe-B alloys with various matrix microstructures were performed using a pin-on-disc tribometer at a normal load of 3 N. The wear behavior was analyzed using s...

Hybrid (Ti5Si3 + TiCx) (x = 0.67) particles reinforced TC4 matrix composites were in-situ prepared by hot-press sintering, basing on the reactions between Ti3SiC2 and Ti. To research the effects of Ti3SiC2 content on the microstructures and mechanical properties, 1–10 wt% Ti3SiC2 were selected. When Ti3SiC2 content was less than 5 wt%, Si element dissolved in the matrix, and TiCx distributed in the matrix homogeneously. While the content exceeded 5 wt%, Si was precipitating as Ti5Si3 attaching to TiCx particles, which resulted in the aggregations of reinforcements. The micro-hardness of matrix was improved with the solid solubility of Si increasing in matrix, and the compressive strength was improved with Ti3SiC2 content increasing. The hardness was mainly affected by solid solution strengthening. The compressive strength was affected by the solid solution strengthening, fine-grain strengthening and the improvement effect of reinforcements. It was determined that solid solution strengthening played the major role by theoretical calculation.

Two-body abrasive wear behavior and mechanism of Fe B alloys with different Mo contents have been systematically investigated. The results show that the Mo addition can promote the formation of Mo-rich and Cr-rich M2B in Fe B alloys, and the Mo-rich and Cr-rich M2B possess the higher H (hardness) and δA (plasticity factor) compared to the Fe-rich M2B. Meanwhile, with the increase of Mo content, the VMo+Cr/VFe increases slightly firstly and then increases rapidly (Where the VMo, VCr and VFe represents the volume fractions of Mo-rich, Cr-rich and Fe-rich M2B, respectively, and the VMo+Cr shows the volume fractions of VMo and VCr). The wear results reveal that the wear rate decreases greatly with the increasing VMo+Cr/VFe, especially when the VMo+Cr/VFe B alloys effectively.

In this work, the high temperature wear behavior of Ca Ti modified high-boron high-speed steel is investigated. The results indicate that the microstructure of the alloy consists of matrix and eutectic borocarbide. Ca Ti modification aims at improving the stability of borocarbide under wear condition through making the distribution of borocarbide more isolated. The wear experiment revealed that the wear resistance of high-boron high-speed steel is much better than that of T15 steel due to the better oxidization resistance and mechanical property of matrix and borocarbide respectively. Under 25 °C and 200 °C, main wear mechanism of high-boron high-speed steel is adhesive spalling. When the temperature is 400 °C, the mechanism becomes combination of adhesive spalling and oxidization. Under 600 °C, the mechanism is oxidation.

The continuous cooling transformation (CCT) curve of an Fe-2.1B (wt%) alloy is obtained using a Gleeble 1500D thermomechanical simulator. The microstructure, mechanical properties, and residual stress of alloy specimens with various cooling rates are examined. The results reveal that the cooling rate has a great influence on the matrix microstructure of the Fe-2.1B (wt%) alloy. Pearlite is formed at the cooling rate of 0.1 K/s, pearlite and martensite are formed in the cooling rate range of 0.2–0.5 K/s, and only martensite remains in the matrix when the cooling rate exceeds 0.5 K/s. In addition, as the cooling rate increases, the dislocation density in the matrix increases, and this, in turn, leads to an increase in the volume fraction of the M23(B, C)6 phase. The precipitation of M23(B, C)6 causes the decrease in the (B + C) contents of the matrix, which, in turn, reduces the microhardness of the matrix to some extent. Meanwhile, the large residual compressive stress of the alloy increases with increasing cooling rate. The maximum residual compressive stresses induced by the cooling rates of 0.5 and 30 K/s are approximately 18% and 36%, respectively, higher than that induced by the cooling rate of 0.1 K/s. Moreover, when the cooling rate increases from 0.1 K/s to 0.5 K/s, the macrohardness and bending stress increase significantly owing to an increase in Vm/Vpr (where Vm represents volume fraction of martensite, Vpr is the volume fractions of pearlite and austenite). When the cooling rate exceeds 0.5 K/s, the macrohardness and bending stress decrease gradually because of the decrease in the (B + C) contents of the matrix and an increase in the residual stress. The critical cooling rate (0.5 K/s) may be the optimal cooling rate of Fe-B alloys.

In this work, the effect of solidification rate on the microstructure and impact toughness of high boron high speed steel is systematically investigated. The theoretical and experimental results indicate that the as-cast microstructure of high boron high speed steel consists of α-Fe matrix and eutectic borocarbide. Without Ca-Ti addition, borocarbide presents a continuous and reticular structure. After Ca-Ti modification, borocarbide possesses an isolated, fine structure. Besides, cooling rate obviously affects the extent of spheroidization. In modified high boron high speed steel, calcium possesses surface activity, which restrains the growth of eutectic borocarbide during solidification. Titanium exists in the form of dispersedly distributed TiC particles which act as heterogeneous nuclei for eutectic borocarbide. The impact toughness of high boron high speed steel is remarkably improved by Ca-Ti modification, which can be further improved by cooling rate. The effect of cooling rate on improving of the toughness can provide a scientific basis for the foundry process designing.

Certain amounts of precipitate in CoCrFeNiMox (simplified as Mox) is beneficial to the wear resistance, however, the optimal chemical content of Mo and the anti-wear mechanism behind it remains unclear. The Mox (x = 0, 0.3, 0.5, 1, 1.5 in molar ratio) high entropy alloys (HEAs) were manufactured, the evolution of their microstructure, mechanical, friction, and wear properties with Mo content was studied. The results displayed that the mechanical properties of the FCC solid solution were enhanced from Mo0 to Mo0.3, then kept unchanged till x = 1.5. The volume fraction of the precipitates increased with Mo content. The Mo1 presents the lower average friction coefficient and wear rate, attributed to the desired types, amount, size, distribution of the hard σ and μ phases in the ductile FCC solid solution. The detailed mechanism behind their tribological behaviors were discussed in the manuscript.

In postgraphene two-dimensional materials (2DMs), MoS

During the abrasive wear process of Fe-B alloy, the Fe2B resists the abrasive and protects the matrix from being shoveled off; in return, the matrix supports the Fe2B against fracture. Therefore, there is a need to characterize the effect of matrix on the abrasion resistance of Fe-B alloy. Two-body abrasive wear tests of as-cast Fe-B alloys with various matrix contents are performed on a pin-on disk tribometer at the normal load ranging from 7 N to 30 N. At the load of 7 N, the abrasion resistance of Fe-B alloy increases with increased Cu and Ni contents, especially for the high Cu and Ni additions (namely, the Vm/Vp becomes greater than 3.7 (where the Vp and Vm show the volume fractions of pearlite and martensite, respectively)), and the wear mechanism changes from micro-ploughing to micro-cutting. Nevertheless, the abrasion resistance of Fe-B alloy decreases with the increase of normal load. At the same time, the wear mechanism changes from micro-cutting to a mixed mode of micro-cutting and micro-ploughing. The wear mechanism of Fe-B alloy can be described as follows: with the decrease of Vm/Vp or the increase of normal load, the M2B-type boride will be crushed by a perpendicular force F⊥ owing to a high degree of deformation, and the broken M2B debris will be eradicated and dislodged by the Al2O3 abrasives, then the abrasion resistance of Fe-B alloy will be reduced greatly. Accordingly, it has been proven that the Fe-B alloy with martensite matrix or high Vm/Vp matrix can be effectively subjected to severe abrasive wear in a low contact stress.

Effects of casting thickness on microstructure, mechanical properties and abrasion resistance of Fe-B cast alloy have been systematically investigated. The results show that the microstructures of as-cast Fe-B alloy mainly consist of martensite, pearlite and M2B; with increasing of casting thickness, the Vm/Vp (where Vp shows volume fraction of pearlite and Vm shows volume fraction of martensite) decreases, while the morphology, composition and Vb (volume fraction of boride) of Fe-B alloy are nearly unchanged. Moreover, with increasing of casting thickness, the microhardnesses of martensite, pearlite and M2B have little change, while the bulk hardness of as-cast Fe-B alloy decreases in a line relationship (y = −0.33x+64.67) owning to the decreasing of Vm/Vp. During wear process, the predominant wear mechanism of as-cast Fe-B alloy may change from microcutting to microploughing with decreasing Vm/Vp, resulting in the more and more boride being crushed by F⊥. As a result, the wear weight loss of Fe-B increases (i.e. the abrasion resistance decreases) with the decreasing of Vm/Vp, indicating that the Vm/Vp has positive influence on abrasion resistance of Fe-B cast alloy.

As a new rising star in the post-graphene two-dimensional materials (2DMs), molybdenum disulfide (MoS2) attracts increasing attentions and is widely applied. However, the chemical and toxicological interaction between MoS2 and other co-contaminants is still poorly understood. Nano-silver (N-Ag) is the most commonly used nanomaterial in commercial products and distributed widely in the environment. Herein, we investigated the effects of chitosan functionalized MoS2 (CS-MoS2) nanosheets, a water-dispersible form of MoS2, on the microbial toxicity of N-Ag. We found that the incorporation of CS-MoS2 nanosheets attenuated the oxidative stress induced by N-Ag on yeast cells, while caused more membrane stress. In addition, the inhibition of N-Ag on the metabolic activities of yeast cells could be attenuated by CS-MoS2 nanosheets as well. The coexistence of N-Ag and CS-MoS2 nanosheets mainly perturbed the amino acid-related metabolic pathways in yeast cells, and phosphoric acid was a potential nanotoxicity biomarker. We further found that CS-MoS2 nanosheets dramatically absorbed the Ag ion released from N-Ag, which might be responsible for its attenuation effect on the microbial toxicity of N-Ag. Our findings provide more new insights for the ecotoxicity evaluation of MoS2 and other 2DMs.

The microstructure, mechanical properties and abrasion resistance of Fe-B alloy with 4wt%Cr-2wt%Mn-2wt%Cu addition have been systematically investigated. The results show that the microstructures mainly consist of martensite and boride (M2B) in the as-cast and heat treated Fe-B alloys; after heat treatment, the morphology and volume fraction of the M2B have little change, meanwhile the nucleation and precipitation of secondary borocarbide M23(C, B)6 probably take place in an in situ manner within martensite. Moreover, the M2B is identified as chemical formula of Fe2.04Cr0.11Mn0.07(B, C) reflecting body-centred tetragonal (bct) structure, and the secondary borocarbide M23(B, C)6 has the stoichiometry of Fe18.84Cr2.84Mn0.57(B, C)6 with face-centred cubic (fcc) structure. After heat treatment, the matrix hardness and bulk hardness of Fe-B alloy decrease owing to the decreasing of B/C concentration of matrix caused by the precipitation of M23(C, B)6, while the fracture toughness of Fe-B alloy increases. Meanwhile, the heat treatment will decrease the wear resistance of Fe-B alloy, i.e. the wear resistance of Fe-B alloy would decrease with reduction of the matrix hardness.

In order to improve the hardenability and toughness of high boron alloys, X Cu ( X = 0, 0.5, 1, 1.5, 2, 3, weight %) were added into high boron alloys. The Cu precipitation behavior and its effect on hardenability, microstructure, crystallography and mechanical properties of as-cast Fe-B-C-Cu alloys have been investigated systematically by means of SEM, XRD, TEM, EPMA and EBSD. The results indicate that Cu improves the hardenability of Fe-B-C-Cu alloys, while excessive Cu atoms segregating at the matrix attaching to boride promote the appearing of nano-Cu precipitation with body-centred cubic (bcc)structure, which can act as heterogeneous nuclei of the pearlite, leading to the reduction of hardenability. Therefore, the Cu concentration in Fe-B-C-Cu alloys should be controlled below 2 wt%. Observation of TEM reveals that the orientation relationship(OR) between martensite and retained austenite are [001] α // [011] γ and [110] α //[ 1 ( − ) 1 ( − ) 1] γ. As well, the OR between ferrite and M 3 C are (100) M // (010) M3C and [011] M //[001] M3C . EBSD analysis shows that the misorientation angles of the α-Fe and M 2 B phases are mainly low-angle with less than 5°. The α-Fe phase has the preferred crystal plane (111) // ND-type grain, while the M 2 B phase displays a preferred growth orientation [002] on the M 2 B crystal plane (001). A possible OR between borides and α-Fe in Fe-B-C-Cu alloys is (001) α- Fe //(001) M2B . In addition, the bulk hardness and impact toughness increase obviously with 1–2 wt% copper concentration owing to the increasing of volume fraction of martensite( V m ), which maybe a guiding copper addition in Fe-B-C-Cu alloys.

In postgraphene two-dimensional materials (2DMs), MoS2 has attracted increasing attention in the biomedical field due to its excellent physicochemical properties. However, the toxicity and biocompatibility evaluation of MoS2 is not fully addressed. Herein, chitosan functionalized MoS2 (CS-MoS2) nanosheets, which showed perfect dispersibility and stability performances, were synthesized and characterized. We found that CS-MoS2 nanosheets inhibited the viability of human dermal fibroblasts (HDFs) moderately while causing cell membrane instability, ROS generation, and DNA damage in a dosage-dependent manner. CS-MoS2 nanosheets did not induce significant changes in the cell morphologies, but they seemed to impair the cell division of HDFs. CS-MoS2 nanosheets (100 μg/mL) activated EGFR and induced reactive oxygen species, Smad, and IL-1, which in turn led to cell inflammation and apoptosis. Furthermore, HDFs showed cellular stress responses when they were exposed to low concentrations of CS-MoS2 nanosheets (25...

The microstructure of machined surfaces is crucial to the overall performance and service life of mechanical structures. In this study, we performed cutting experiment, test analyze, and theoretical calculation to investigate the evolution in gradient microstructures of the superficial layer on machined surface, including grain size, dislocation density, grain boundary and misorientation angle, in the turning of high strength alloy steel with a self-developed coated carbide microstructure turning tool under different cutting velocities. Single-factor cutting experiments and corresponding tests were carried out using X-ray diffraction (XRD) and electron back scattered diffraction (EBSD) to investigate effects of cutting velocity on the microstructure of the machined surface during the cutting process. In addition, the performance and quality of the machined surfaces were assessed using a micro-hardness tester, laser scanning confocal microscopy, and atomic force microscopy. The relationship between microstructure and performance of the machined surface was explored by establishing a cutting model. The results showed that higher cutting velocities before exceeding the transition threshold with a larger relative evaluation coefficient can raise the thickness of the strengthening layer. This changes the gradient-distribution of dislocation density, grain boundary, and misorientation angle in the machined surface resulting in finer grains, thereby strengthening the machined surface. Moreover, the thickest agglomerate layer of equiaxed crystals was also observed under the higher cutting velocity, which was found to improve the performance of the workpiece (Micro-hardness of 318.07 HV and roughness of 0.05 μm), suggesting the approach to control cutting conditions to achieve better machined surfaces by evaluating the comprehensive function of mechanical load and thermal load in the metal machining process is effective.

Body-centered cubic (BCC) multi-principal element alloys (MPEAs) have drawn extensive attention for their interesting structures and good mechanical properties. However, most BCC MPEAs lack ductility at room temperature. Decreasing the valence electron concentration (VEC) value is an effective approach to design the BCC MPEAs with intrinsic ductility. Three TiZr-rich MPEAs (Ti45Zr45Nb5Ta5, Ti45Zr45Nb5Mo5, and Ti42.5Zr42.5Nb5Mo5Ta5) were designed in this paper, by controlling their VEC through restricting the contents of group V (Nb, Ta) and group VI (Mo) elements into 5 at.%. These alloys all possessed BCC structure, low elastic modulus (56–74 GPa), and intrinsic ductility in the as-cast status. Among the three MPEAs, Ti42.5Zr42.5Nb5Mo5Ta5 exhibited the finest microstructure, as well as the highest tensile yield strength (~907 MPa) and elongation (~14.9%). The theoretical calculation indicates that the high strength of Ti42.5Zr42.5Nb5Mo5Ta5 alloy was dominantly attributed to solid solution strengthening. The results also show that Mo element possesses a stronger solution strengthening effect than Ta, as it has a wide difference of shear modulus compared to the other constituent elements.

In sliding wear process, the wear reaction existing between hard phase and metallic matrix has an important effect on the wear performance of alloy. The purpose of this work is to quantitatively characterize the effect of matrix on the wear interaction in an Fe-2wt%B alloy. The results show that the wear interaction makes a positive contribution to the abrasion resistance of alloy, and increases with the increased Vm/Vp (where Vm and Vp show the volume fractions of martensite and pearlite respectively). Moreover, the contribution of matrix to the wear interaction changes with the Vm/Vp. When the Vm/Vp