Establishment of Constitutive Model and Analysis of Dynamic Recrystallization Kinetics of Mg-Bi-Ca Alloy during Hot Deformation

The flow behavior of the solution-treated Mg-3.2Bi-0.8Ca (BX31, wt.%) alloy was systematically investigated during hot compression at different deformation conditions. In the present study, the strain-related Arrhenius constitutive model and dynamic recrystallization (DRX) kinetic model were established, and the results showed that both two models had high predictability for the flow curves and the DRX behavior during hot compression. In addition, the hot processing maps were also made to confirm a suitable hot working range. Under the assistance of a hot processing map, the extrusion parameters were selected as 573 K and 0.5 mm/s. After extrusion, the as-extruded alloy exhibited a smooth surface, a fine DRX structure with weak off-basal texture and good strength–ductility synergy. The newly developed strong and ductile BX31 alloy will be helpful for enriching low-cost, high-performance wrought Mg alloy series for extensive applications in industries

Role of Zn addition on the microstructure and tensile property in Mg–Mn–Nd alloys

The role of Zn addition (1, 2 wt%) on the microstructural characteristics and tensile properties of the extruded Mg–1Mn–1Nd (MN11) alloy is discussed. The addition of Zn negligibly influences the particle type; however, Zn addition causes un–homogeneous distribution structure firstly and then develops homogeneous structure because of the change of size and distribution of Mg12Nd particles. The MZN111 sheet shows higher yield strength (YS) along the extrusion direction (ED), and lower YS along the transverse direction (TD), compared to the MN11 sheet. This improvement is attributed to the Zn solute atoms via solid-solution strengthening effect, while the reduction is ascribed to the formation of TD–orientation texture and coalescence of dynamic recrystallized (DRXed) grains. As the Zn content increases to 2 wt%, The MZN121 sheet with highest strength can be ascribed to the homogeneous distribution of finest grains via the grain–boundary strengthening effect and more Zn solute atoms via solid–solution strengthening effect. The increased size of Mg12Nd particles with 1 wt% Zn content and coalescence of DRXed grains, which can significantly reduce the ductility of MZN111 sheet. Further, the ductility enhancement of the MZN121 sheet is mainly due to the homogeneous distribution of fine grains and homogeneous alignment of Mg12Nd particles

Effect of Bi Addition on the Heat Resistance of As-Extruded AZ31 Magnesium Alloy

In this work, we investigate the impact of Bi addition on the heat resistance of as-extruded AZ31 alloy during high-temperature annealing and hot compression. Electron backscattered diffraction (EBSD) technique and quasi in situ scanning electron microscopy (SEM) are used to analyze the evolution of microstructures during high-temperature annealing and hot compression, respectively. The test results show that with a prolonged annealing time, the as-extruded AZB313 alloy exhibited a lower grain growth rate, due to the pinning effect of Mg3Bi2 phases distributed at grain boundaries. On the other hand, as the compressive temperature increased, the downtrend of strength is delayed in the as-extruded AZB313 alloy. Thermally stable Mg3Bi2 phases dispersed within the grains act as barriers, hindering the motion of dislocations, which not only provides a more effective precipitation strengthening effect, but also increases the resistance to deformation of grains. Moreover, grain boundary sliding can also be restricted by Mg3Bi2 phases located at grain boundaries. This work provides a new idea for the development of heat-resistant wrought Mg alloys

Achieving extremely high speed extrusion and medium strength in a Mg–Bi–Si ternary alloy

In this work, we report a new Mg–5Bi–1Si (wt.%) alloy showing a synergy of extrusion speed (ES) and tensile yield strength (TYS). At high ESs, it still has a good alloy surface, owing to the formation of thermally stable Mg3Bi2 and Mg2Si phases and the disappearance of small-sized low-melting divorced eutectic Mg3Bi2 phases for the as-cast alloy. During 70 m/min extrusion, the fragmentation of pre-existing eutectic (Mg3Bi2 and Mg2Si) phases and the dynamic precipitation of new (Mg3Bi2) phases impede the excessive grain coarsening and provide the effective strengthening contributions on the TYS of ∼253 MPa. After T5 peak aging, two types of basal Mg3Bi2 precipitates are found and further enhance the TYS to ∼280 MPa

Establishing the HPLC-MS/MS Method for Monitoring the Residue and Degradation of Butralin in Ginseng during Field and Risk Assessments

Butralin can effectively mitigate the spreading of weeds in ginseng fields, however, the dissipation and residues of butralin in ginseng have not been investigated. In this study, we established a high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method to determine the butralin residue and its dissipation in ginseng and its dietary intake risk. The mean recoveries of butralin in ginseng (fresh, dried, plants, and soil) ranged from 93.1–107.5% with relative standard deviations of 0.7–6.4%. The half-lives of butralin in ginseng plant and soil were 10.81–18.91 days, and its final residues in ginseng, dried gingeng, gingeng plant, and soil were <0.01, <0.010–0.02, 0.011–0.19, and 0.162–0.410 mg/kg, respectively. The dietary risk quotient of butralin was 3.25 × 10−4, which suggests that the consumption of butralin-treated ginseng during the harvest period does not affect human health

The Combustion of Forest Humus Blended with Low-Rank Coal: Effects of Oxygen Ratio and Blending Ratio

In this study, the combustion characteristics of pine needles, pine needle humus, and the co-combustion of these two types of biomass with coal were compared. In addition, the optimization of the combustion performance of coal/humus was assisted through the following studies: (i) the combustion performance of coal/pine needle humus was studied under four different oxygen concentrations (N2, 10%O2/90%N2, 20%O2/80%N2, and 40%O2/60%N2); (ii) the synergistic effect between the humus and coal during combustion was also investigated by adjusting the blending ratio and oxygen content; (iii) the mechanisms of the optimized combustion processes were expounded by kinetics and thermodynamics discussion. The results demonstrated that the combustion characteristics of the coal/humus blends were found to be higher than those of the coal/pine needle blends. The coupling interactions of the oxygen content and blending ratio contributed to the significant synergistic effect between the two fuels, and the synergistic effect showed a nonlinear variation with an increased oxygen concentration. The synergistic effect in a rich oxygen environment (O240%/N260%) is 5.1 times greater than that in the synthetic air (O220%/N280%) and 13.8 times greater than that in the oxygen-poor environment (O210%/N290%). Hence, the blending ratio could be adjusted to maintain the intensity of the synergistic effect in an oxygen-rich atmosphere

Myofibroblast transformation, senescence and apoptosis of the injured cornea.

<p>(A) The <i>Ikkβ</i>^<i>F</i> and <i>Ikkβ</i> ^<i>ΔCS</i> eyes were harvested at 28 days after alkali burn injury. The tissues were processed and used for immunohistochemistry using anti-α-SMA, a marker for myofibroblast and TUNEL assays for the detection of apoptotic cells. Blue: DAPI (nuclei), Red: leukocytes. (B) The <i>Ikkβ</i>^<i>F</i> and <i>Ikkβ</i> ^<i>ΔCS</i> eyes were harvested at 4 days and 28 days after alkali burn injury. The tissue sections were examined by SA-β-Gal staining. The SA-β-Gal positive cells are stained with blue color. ST: corneal stroma, EP, corneal epithelium, labeled with arrows. (B and D) The number of staining positive cells was quantified and **p<0.01 and ***p<0.001 was considered significantly different between <i>Ikkβ</i>^<i>F</i> and <i>Ikkβ</i> ^<i>ΔCS</i> eyes. Data represent at least at least 5 slides/eye and 3 injured eyes examined.</p

Role of IKKβ in corneal development and maintenance.

<p>(A) The eyes of <i>Ikkβ</i>^<i>F</i> and <i>Ikkβ</i>^<i>ΔCS</i> mice were examined under a stereoscope and photographed. (B) The <i>Ikkβ</i>^<i>F</i> and <i>Ikkβ</i>^<i>ΔCS</i> eyes were analyzed by H&E staining, TUNEL assay and immunostaining using anti-PCNA. Blue: Hoechst for nuclei. Red: TUNEL and PCNA positive signals, which were absent in the cornea of adult mice. ST: corneal stroma, EP, corneal epithelium, labeled with arrows. Pictures represent results from at least 3 mouse corneas of each genotype.</p

Corneal Wound Healing Requires IKB kinase β Signaling in Keratocytes

<div><p>IkB kinase β (IKKβ) is a key signaling kinase for inflammatory responses, but it also plays diverse cell type-specific roles that are not yet fully understood. Here we investigated the role of IKKβ in the cornea using <i>Ikkβ</i>^<i>ΔCS</i> mice in which the <i>Ikkβ</i> gene was specifically deleted in the corneal stromal keratocytes. The <i>Ikkβ</i>^<i>ΔCS</i> corneas had normal morphology, transparency and thickness; however, they did not heal well from mild alkali burn injury. In contrast to the <i>Ikkβ</i>^<i>F/F</i> corneas that restored transparency in 2 weeks after injury, over 50% of the <i>Ikkβ</i>^<i>ΔCS</i> corneas failed to fully recover. They instead developed recurrent haze with increased stromal thickness, severe inflammation and apoptosis. This pathogenesis correlated with sustained myofibroblast transformation with increased α smooth muscle actin (α-SMA) expression, higher levels of senescence β-Gal activity and scar tissue formation at the late stage of wound healing. In addition, the <i>Ikkβ</i>^<i>ΔCS</i> corneas displayed elevated expression of hemo-oxygenase-1 (HO-1), a marker of oxidative stress, and activation of stress signaling pathways with increased JNK, c-Jun and SMAD2/3 phosphorylation. These data suggest that IKKβ in keratocytes is required to repress oxidative stress and attenuate fibrogenesis and senescence in corneal wound healing.</p></div

Corneal wound healing in <i>Ikkβ</i>^<i>F</i> and <i>Ikkβ</i> ^<i>ΔCS</i> mice.

<p>The <i>Ikkβ</i>^<i>F</i> and <i>Ikkβ</i> ^<i>ΔCS</i> mice were subjected to mild alkali burn corneal injury, and the eyes were examined under a stereoscope and slit lamp. (A) Representative photos of the eyes at different days after injury, and (B) the average opacity score are presented as mean±SEM of at least 8 eyes examined under each genotype/experimental conditions. Significant differences between groups were calculated using 2-way repeated measures ANOVA followed by post hoc multiple comparisons of means (Tukey method), and *<i>p</i> < 0.05 is considered statistically significant between the genotypes on the given days of injury. (C) The wounded eyes were harvested at different days after injury and examined by H&E. ST: corneal stroma, EP, corneal epithelium, labeled with arrows.</p