Aims
The objective of this study was twofold: (i) to examine the effect of Clostridium butyricum on intestinal barrier function and (ii) to elucidate the mechanisms involved in enhanced intestinal ...barrier function.
Methods and Results
Forty‐eight weaned piglets were assigned randomly to either a basal diet or a C. butyricum‐supplemented diet. On day 15, all pigs were orally challenged with enterotoxigenic Escherichia coli (ETEC) K88 or saline. Clostridium butyricum decreased serum diamine oxidase activity and d‐lactic acid concentration, as well as increased intestinal tight junction proteins (ZO‐1, claudin‐3 and occludin) expression in ETEC K88‐infected pigs. Moreover, C. butyricum decreased IL‐1β and IL‐18 levels in serum and gut, whereas it increased IL‐10 levels. Furthermore, C. butyricum downregulated NLRP3 and caspase‐1 expression in ETEC K88‐challenged pig gut, but did not affect apoptosis‐associated speck‐like protein expression.
Conclusions
Clostridium butyricum enhanced intestinal barrier function and inhibited apoptosis‐associated speck‐like protein‐independent NLRP3 inflammasome signalling pathway in weaned piglets after ETEC K88 challenge.
Significance and Impact of the Study
The novelty of this study lies in the beneficial effects of C. butyricum on intestinal health, likely by improving intestinal barrier function and alleviating inflammatory reactions.
Refractory high-entropy alloys hold the potential for high-temperature applications beyond the capability of the state-of-the-art Ni-based superalloys, and thus, it is important to study their solid ...solution formation characteristics and mechanical properties. In this study, designed by CALPHAD method, formation of as-cast arc-melted body-centered cubic MoNbTaTiV was experimentally verified using X-ray diffraction and scanning electron microscopy. The measured density and lattice parameter for MoNbTaTiV are 9.29g/cm3 and 3.224 Å, which obey the rule of mixtures (ROM). The alloy exhibits high hardness at 443 Hv, high yield strength at 1.4 GPa, and good compressive fracture strength at 2.45 GPa with a fracture strain of ∼30% at room temperature. The yield strength and hardness values of this alloy, and other single-phase refractory high-entropy alloys, are estimated using a simple model of solid solution strengthening. Reasonable agreement between modeling prediction and experiments is obtained. In addition, first-principles density functional theory calculations predict an enthalpy of formation of −0.865 kJ/mol for the MoNbTaTiV alloy, with calculated atomic volume and elastic properties (e.g., bulk and elastic moduli) obeying the ROM.
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•MoNbTaTiV exhibits the BCC structure, agreeing with CALPHAD calculations.•Predicted solid solution strengthening agrees well with experiments.•Hardness of BCC high entropy alloys is about three times the yield strength.•Calculated atomic volume and bulk and shear moduli obey the rule of mixtures.
The formation of disordered solid solution in the hexagonal close-packed (hcp) structure in the GdHoLaTbY alloy and its mechanical properties were investigated in this study. The single hcp phase of ...the alloy in the as-cast state was confirmed by X-ray diffraction and scanning electron microscopy analyses. The compressive yield strength, fracture strength, and plastic strain of the alloy are 108MPa, 880MPa, and 21.8%, respectively, and the Vickers hardness is 96HV. The results show that the yield strength, fracture strength, and hardness of the alloy obey the rule of mixture, which indicates that there is no hardening effect from entropy. Although the high entropy of mixing stabilizes the solid solution against intermetallic compounds, lack of severe lattice distortion from elastic strain or electronic interactions between principal elements impacts little on the mechanical properties.
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•The GdHoLaTbY high-entropy alloy forms a hexagonal close-packed solid solution.•The strengthening effect from the configurational entropy is not found in the alloy.•The mechanical properties and Vickers hardness of the alloy obey the rule of mixture.
This study reports the design and development of ductile and strong refractory single-phase high-entropy alloys (HEAs) for high temperature applications, based on NbTaV with addition of Ti and W. ...Assisted by CALPHAD modeling, a single body-centered cubic solid solution phase was experimentally confirmed in the as-cast ingots using X-ray diffraction and scanning electron microscopy. The observed elemental segregation in each alloy qualitatively agrees with CALPHAD prediction. The Vickers microhardnesses (and yield strengths) of the alloys are about 3 (and 3.5–4.4) times that those estimated from the rule of mixture. While NbTaTiVW shows an impressive yield strength of 1420MPa with fracture strain of 20%, NbTaTiV exhibits exceptional compressive ductility at room temperature.
The deformation responses of NiCoCrFe high-entropy alloy (HEA) under quasi-static (1 × 10−4-1 × 10−1/s) and dynamic (1,000–6,000/s) tension were investigated. A good combination of high strength and ...ductility is obtained under dynamic tension. The yield strength and true ultimate tensile strength is increased from 217 to 830 MPa at 1 × 10−4/s to 440 MPa and more than 1,000 MPa at 6,000/s, respectively. In addition, the engineering fracture strains maintain 60%–85% over a wide range of strain rates. The enhancements of strength and ductility originate from (1) the significant strain-rate sensitivity (SRS) mainly due to the presence of short-range orders/clusters (SROs/SRCs) as well as phonon drag effect of dislocations, and (2) the extraordinary work-hardening capacity due to dynamically formed nanoscale twins upon high strain-rate tension. The temperature and strain-rate dependence of the yield strength of the alloy are well modeled based on the thermally activated mechanism. Additionally, considering nanoscale twin boundaries as local sites for nucleating and accommodating dislocations, the dislocation density evolution model is modified and subsequently introduced into Taylor hardening model to accurately capture the hardening behavior of the current NiCoCrFe HEA. Hence, the distinguished work-hardening capacity under dynamic tension can be mainly ascribed to the low dislocation recovery rate and remarkable twin-induced dislocation generation.
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•NiCoCrFe HEA possesses simultaneous enhancement of strength and ductility at high strain rates (greater than 1,000/s).•Strong strain rate sensitivity originates from short-range orders/clusters and phonon drag effect of dislocation.•Extraordinary strain hardening mainly stems from the dynamically formed nanoscale twins.•A strain rate-dependent model was established to bridge the gap between microstructure and mechanical properties.•Design idea of new alloys serving under cryogenic temperatures and dynamic impacts was given.
A serrated flow, which occurs in a material undergoing mechanical deformation, is a complex process of great engineering significance. Here statistical, dynamical, and multifractal modeling and ...analyses were performed on the stress-time series to characterize and model the stress-drop behavior of an Al0.5CoCrCuFeNi high-entropy alloy (HEA). Results indicate that the spatiotemporal dynamics of the serrated flow is affected by changes in the strain rate and test temperature. The sample entropy, in general, was found to be the highest in the samples tested at 500 °C. The higher complexity in the serrated flow at this temperature appeared to be associated with the stress-drop behavior that had intermediate values in terms of the maximum stress drop, the multifractality of the data set, and the histogram distributions. Moreover, the sample entropy was the lowest for the samples tested at 600 °C. The lower complexity values were associated with a wider multifractal spectrum and a less uniform and sparser distribution of the stress-drop magnitudes. In terms of the serration types, Type-C serrations were related to the lowest complexity values, widest multifractal spectra, and higher probability of exhibiting larger stress drops. Conversely, Type-A and B serrations were associated with the higher complexity, narrower spectra, and lower probability of higher stress drops. Furthermore, the body-centered-cubic (BCC) structure and the fully-ordered L12 nano-particles were found to emerge in the samples at 600 °C and are thought to be linked to the decreased spatiotemporal correlations in the stress-drop behavior.
•Link between complexity, multifractal, and stress-drop magnitude statistics.•Spatiotemporal dynamics of serrations is affected by strain rate and temperature.•Serrations exhibited the most complex behavior at a strain rate of 2 × 10-3 s-1.•Higher spatiotemporal correlations in the serrated flow at 500oC.
High-entropy alloys (HEAs) with a single-phase face-centered cubic (FCC) structure generally have excellent plasticity. However, its limited room temperature strength and hardness result in lower ...wear resistance, which hinders tribological and engineering applications. In this paper, the pack-boronizing method was used to improve the tribological properties of Al0·1CoCrFeNi HEAs with a single-phase FCC structure. The boronizing treatment was carried out at 900 °C for 2, 4, 6, and 8 h, respectively. The structure and phase formation of boronized alloys were studied. Moreover, the reciprocating sliding wear behavior of boronized alloys against Si3N4 balls in dry and deionized water was investigated. A boronized layer with a double-layer structure was formed on the HEA surface, with a total thickness of about 17.3–58.5 μm. The wear mechanism of boronized alloy was transformed from the abrasive and delamination wear to the polishing effect with increasing the boronizing time in air. In contrast, the wear mechanism of boronized alloys in the deionized water gradually changed from the two-body to three-body wear with increasing the boronizing time. Meanwhile, the wear mechanism of the Si3N4 counterface was also transformed to three-body wear gradually.
•The maximum hardness of boronized HEAs is higher 7 times than that of annealed HEAs.•The wear rate of boronized HEAs was much lower than that of as-cast HEAs.•The wear mechanism of boronized HEAs in air was abrasive wear and polishing effect.•Wear mechanism of HEAs in deionized water was two-body and three-body abrasive wear.•The lubrication of deionized water led to lower friction coefficient and wear rate.
The effect of minor inclusion of rare earth element of lanthanum into a well-established high entropy alloy system of CrMnFeNi on their corrosion resistance properties in different media with various ...concentrations was investigated in this study. The potentiodynamic polarization curves of the CrMnFeNi and CrMnFeNiLa0.1 alloys in acidic solutions exhibit an extensive passive region (ΔE>1100 mV). The Nyquist plot of the La-free CrMnFeNi alloy includes one capacitive loop and one inductive loop and while for the CrMnFeNiLa0.1 alloy only one capacitive loop is present. SEM results show that the morphology of the two alloys is obviously different in different media. XPS data reveals the existence of distinctive content discrepancy of Mn and Ni in passive film between La free and La-containing HEA, strongly implying the considerable impact of La in the passivation process.
•The effect of lanthanum into CrMnFeNi HEA on their corrosion resistance properties is investigated.•The potentiodynamic polarization curves of the HEAs in acidic solutions exhibit an extensive passive region.•XPS results show that inclusion of La leads to content alteration in the passivation film.
High-Entropy Alloys in Hexagonal Close-Packed Structure Gao, M. C.; Zhang, B.; Guo, S. M. ...
Metallurgical and materials transactions. A, Physical metallurgy and materials science,
07/2016, Letnik:
47, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The microstructures and properties of high-entropy alloys (HEAs) based on the face-centered cubic and body-centered cubic structures have been studied extensively in the literature, but reports on ...HEAs in the hexagonal close-packed (HCP) structure are very limited. Using an efficient strategy in combining phase diagram inspection, CALPHAD modeling, and
ab initio
molecular dynamics simulations, a variety of new compositions are suggested that may hold great potentials in forming single-phase HCP HEAs that comprise rare earth elements and transition metals, respectively. Experimental verification was carried out on CoFeReRu and CoReRuV using X-ray diffraction, scanning electron microscopy, and energy dispersion spectroscopy.
In this study, a novel cobalt-free Fe40Mn20Cr20Ni20 (at.%) medium-entropy alloy (MEA) with low cost is purposively designed. The partially recrystallized microstructure was introduced into the ...single-phase FeMnCrNi MEA via thermo-mechanical processing. Surprisingly, the present MEA displays ultrahigh yield and ultimate tensile strengths of 1.2 and 1.34 GPa, respectively, and large ductility with a uniform elongation of 22% at 77 K. This is mainly due to the accumulation and entanglement of a large number of dislocations and the activation of deformation twins at 77 K.
•A novel cobalt-free Fe40Mn20Cr20Ni20 medium-entropy alloy with low cost is purposively designed.•The present medium-entropy alloy displays ultrahigh yielding and ultimate tensile strengths of 1.2 and 1.34 GPa, respectively, and good ductility with a uniform elongation of 22% at 77 K.•Compared with many other advanced alloys, the present MEA has outstanding advantages in the mechanical performances at 77 K and the cost of raw materials for the preparation.
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