Magnesium(Mg)alloys have shown great prospects as both structural and biomedical materials,while poor corrosion resistance limits their further application.In this work,to avoid the time-consuming and laborious experi...Magnesium(Mg)alloys have shown great prospects as both structural and biomedical materials,while poor corrosion resistance limits their further application.In this work,to avoid the time-consuming and laborious experiment trial,a high-throughput computational strategy based on first-principles calculations is designed for screening corrosion-resistant binary Mg alloy with intermetallics,from both the thermodynamic and kinetic perspectives.The stable binary Mg intermetallics with low equilibrium potential difference with respect to the Mg matrix are firstly identified.Then,the hydrogen adsorption energies on the surfaces of these Mg intermetallics are calculated,and the corrosion exchange current density is further calculated by a hydrogen evolution reaction(HER)kinetic model.Several intermetallics,e.g.Y_(3)Mg,Y_(2)Mg and La_(5)Mg,are identified to be promising intermetallics which might effectively hinder the cathodic HER.Furthermore,machine learning(ML)models are developed to predict Mg intermetallics with proper hydrogen adsorption energy employing work function(W_(f))and weighted first ionization energy(WFIE).The generalization of the ML models is tested on five new binary Mg intermetallics with the average root mean square error(RMSE)of 0.11 eV.This study not only predicts some promising binary Mg intermetallics which may suppress the galvanic corrosion,but also provides a high-throughput screening strategy and ML models for the design of corrosion-resistant alloy,which can be extended to ternary Mg alloys or other alloy systems.展开更多
Mg-Y cast alloy shows excellent ductility(elongation to failure>15%)compared with pure Mg and commercial Mg cast alloys.By monitoring the microstructure evolution during an in situ tensile test of a Mg-2.5 wt%Y all...Mg-Y cast alloy shows excellent ductility(elongation to failure>15%)compared with pure Mg and commercial Mg cast alloys.By monitoring the microstructure evolution during an in situ tensile test of a Mg-2.5 wt%Y alloy,we identify the activation of prismatic<c>slip,which is rare in Mg.Synchrotron X-ray micro-beam Laue diffraction(μ-Laue)and transmission electron microscopy revealed the morphology of prismatic<c>slip bands and individual<c>dislocations.Density functional theory and molecular dynamics calculations indicate that solute Y can significantly reduce the stacking fault energy(SFE)along<c>direction on prismatic plane in Mg lattice and thus facilitate the nucleation of<c>dislocations during deformation.The presence of free<c>dislocations in the Mg lattice can also lead to nucleation of{10–12}twins even under unfavorable geometric conditions.展开更多
Background: Double-lumen endotracheal (DLT) is commonly used for one-lung ventilation and lung separation during thoracic surgery. There are case reports of medically induced laryngeal granulomas, mainly in patients a...Background: Double-lumen endotracheal (DLT) is commonly used for one-lung ventilation and lung separation during thoracic surgery. There are case reports of medically induced laryngeal granulomas, mainly in patients after single-lumen endotracheal (SLT) tube intubation and tracheotomy, and giant granulomas of the vocal cords due to double-lumen bronchial tube insertion have rarely been reported. Case presentation: A 49-year-old female patient underwent single-port thoracoscopy after DLT intubation as well as a wedge resection of the lower lobe of the left lung, which caused giant vocal process granulomas (VPGs) postoperatively. Based on a retrospective analysis of the general condition, current medical history, past medical history, and visual laryngoscopic observation of the vocal folds tissue, which ruled out preoperative vocal fold granuloma formation, we hypothesized that double-lumen bronchial catheter intubation may have been the primary cause of her vocal fold granuloma formation. Conclusions: Giant granuloma of the vocal folds after DLT insertion is a rare postoperative complication;therefore, if DLT intubation is to be performed, the anesthesiologist should choose an appropriate intubation plan and deal with it promptly to avoid the risk factors to ensure that the patient’s perioperative period is safe and smooth. In addition, if postoperative complications are encountered, they should be followed up and observed on time.展开更多
Molecule hydrogen(H_(2)) has been used to suppress tumor growth. To employ the H_(2) therapy, it is necessary to use a proper agent for continuous generation of H_(2). As a biodegradable metal, magnesium(Mg) generates...Molecule hydrogen(H_(2)) has been used to suppress tumor growth. To employ the H_(2) therapy, it is necessary to use a proper agent for continuous generation of H_(2). As a biodegradable metal, magnesium(Mg) generates H_(2) in an aqueous environment, but the H_(2) release rate is still too low. Here, we design a Mg-Al-Ca(AX) alloy that degrades very rapidly due to the presence of a secondary phase Al_(2)Ca. Having a reduction potential much higher than Mg and any other Mg-based secondary phases, Al_(2)Ca accelerates the corrosion of the Mg matrix by a micro-galvanic process. Al_(2)Ca also enhances the strength and ductility of the AX alloy. AX alloy rods show better anti-tumor efficacy than pure Mg rods in vivo. Moreover, implanted AX alloy rods can be heated under an alternating magnetic field to suppress large-size tumors.This work suggests that the H_(2) therapy using highly degradable Mg alloys may provide an effective cancer treatment.展开更多
The local deformation behavior and dynamic recrystallization of a shock compressed Mg-1Zn alloy was investigated through EBSD and TEM.Since dislocation slipping and twinning were locally suppressed during high strain-...The local deformation behavior and dynamic recrystallization of a shock compressed Mg-1Zn alloy was investigated through EBSD and TEM.Since dislocation slipping and twinning were locally suppressed during high strain-rate deformation,a more flexible kinking deformation was activated to adjusted local orientation and facilitate slipping and twinning within the kinks.Meanwhile,due to the slow heat dissipation that resulted in a local temperature elevating,the kink bands were evolved into deformation bands with recrystallized nano-grains.Such a finding provides a new perspective for kinking-facilitated nanocrystallization in Mg alloys and other anisotropic metallic materials.展开更多
Mathematical models were proposed to clarify the effect of alloying on corrosion of magnesium alloys based on film-free and film-covered status. The models are applicable to explain the “barrier effect” by cathodes ...Mathematical models were proposed to clarify the effect of alloying on corrosion of magnesium alloys based on film-free and film-covered status. The models are applicable to explain the “barrier effect” by cathodes and the “analogous Hall-Petch relationship” between corrosion rates and grain size. The slope of corrosion rates versus alloying content is determined by the dissolution ability of film-free substrate and the hindering effects by corrosion product film. Designing strategy for corrosion-resistant Mg alloys is established.展开更多
Few studies were reported on the phases'relationships of AE44(Mg-4.0Al-4.1RE-0.3Mn,wt.%)and its composites.In this work,AE44 alloy and Saffil(6-Al2O3)/AE44 Metal matrix composite(MMC)were both prepared by slow sho...Few studies were reported on the phases'relationships of AE44(Mg-4.0Al-4.1RE-0.3Mn,wt.%)and its composites.In this work,AE44 alloy and Saffil(6-Al2O3)/AE44 Metal matrix composite(MMC)were both prepared by slow shot high pressure die casting(SS-HPDC)technology and their phase constitutions were all studied in detail using experimental techniques combined with CALPHAD(Calculation of Phase Diagram)modeling.The results revealed that the alloy consists of the a-Mg matrix,A1hRE3 intermetallic phase,and one trace phase AI3RE,while the composite contains five major phases:a-Mg,5-AI2O3,AI3RE,MgO and Mg2Si.and two trace phases of A12RE and AI11RE3,respectively.A1hRE3 is partly derived from ALRE,while A13RE is a product of the peritectoid reaction between the two precipitates.The presence of MgO and Mg2Si is due to the interfacial reaction between the SiO2 binder in the fiber preforms and the molten magnesium during infiltration.The use of SiO2 binder in the preform manufacturing was limited/minimized to reduce the MgO formation in the MMC casting process,which can be detrimental to the fatigue performance of the MMC materials.展开更多
Alloying elements can drastically alter the deformation behavior of Mg.In the present work,Visco-Plastic Self-Consistent(VPSC)modeling was employed to investigate the effect of alloying elements on Mg’s tensile behav...Alloying elements can drastically alter the deformation behavior of Mg.In the present work,Visco-Plastic Self-Consistent(VPSC)modeling was employed to investigate the effect of alloying elements on Mg’s tensile behavior,in particular the relative activity of different slip and twinning modes.Mg-0.47 wt.%Ca,Mg-2 wt.%Nd,and AZ31 extruded alloys were deformed by micro-tensile tests in a scanning electron microscope(SEM).Texture and grain size measured by electron backscatter diffraction(EBSD)were used as the input for VPSC.After parameter optimization,the VPSC model successfully reproduced the stress-strain curve of each alloy.Simulation results indicate that the slip/twinning activity in the three alloys are different.Mg-0.47 wt.%Ca shows strong extrusion texture,and prismatic slip was quite active during its tensile deformation.In contrast,Mg-2 wt.%Nd shows weak extrusion texture,and basal slip was dominant.This alloy also developed more twinning activity than the other two alloys.AZ31 shows strong extrusion texture similar as Mg-0.47 wt.%Ca,but prismatic slip was less active in it.The slip/twinning activity revealed by the VPSC model can explain the difference in the tensile behavior of the three alloys.展开更多
The 3D visualization of the porosity in high-pressure die casting(HPDC)Mg alloys AZ91D and Mg4Ce2Al0.5Mn(EA42)was investigated by X-ray computed tomography.It was demonstrated that the volumetric porosity at the near-...The 3D visualization of the porosity in high-pressure die casting(HPDC)Mg alloys AZ91D and Mg4Ce2Al0.5Mn(EA42)was investigated by X-ray computed tomography.It was demonstrated that the volumetric porosity at the near-gate location for alloy EA42 was significantly higher than that far from the gate location.This difference resulted from the low valid time during intensified casting pressure conditions.Specimens of alloy EA42 exhibited a narrow pore distribution in the side view(~0.5 mm)compared to the wide distribution(~1.8 mm)of alloy AZ91D,which was mainly attributed to the formation mechanism of the defect band.The formation of microporosity in the defect band of alloy EA42 was inhibited because of the significant latent heat released by a large amount of the Al11Ce3phase segregated in the defect band during solidification.Additionally,an effective estimator(Z-Propagation)was introduced,which is proposed to predict the projected area fraction of the porosity(f)involved during tensile failure with better effectiveness compared with traditional methods based on the actual fractured surface.By coupling the Z-Propagation method with the critical local strain model,the logarithmic fracture strain and true fracture stress of the specimens were predicted within 3.03%and 1.65%of the absolute value of the average relative error(AARE),respectively.展开更多
Static recrystallization of a high strain rate compressed Mg-1 Zn(wt.%)alloy was investigated using electron backscattered diffraction(EBSD).A novel 53°1010 structure was observed in the as-deformed alloy,which s...Static recrystallization of a high strain rate compressed Mg-1 Zn(wt.%)alloy was investigated using electron backscattered diffraction(EBSD).A novel 53°1010 structure was observed in the as-deformed alloy,which showed a{1012}-{1012}double twin relationship with the matrix.When the as-deformed alloy was annealed at 200°C,the{1011}compression twins and{1011}-{1012}double twins showed a higher priority to recrystallize.In addition,the coarse{1012}tension twins and their inner double twins were preferentially to recrystallize,while the lenticular tension twins had little impact on the recrystallization.Therefore,obtaining more compression twins or coarse twins instead of lenticular tension twins can be an effective approach to manipulate recrystallization process in deformed Mg alloys.展开更多
Semiconductor photocatalysis, as a key part of solar energy utilization, has far-reaching implications for industrial, agricultural, and commercial development. Lack of understanding of the catalyst evolution and the ...Semiconductor photocatalysis, as a key part of solar energy utilization, has far-reaching implications for industrial, agricultural, and commercial development. Lack of understanding of the catalyst evolution and the reaction mechanism is a critical obstacle for designing efficient and stable photocatalysts. This review summarizes the recent progress of in-situ exploring the dynamic behavior of catalyst materials and reaction intermediates. Semiconductor photocatalytic processes and two major classes of in-situ techniques that include microscopic imaging and spectroscopic characterization are presented. Finally, problems and challenges in in-situ characterization are proposed, geared toward developing more advanced in-situ techniques and monitoring more accurate and realistic reaction processes, to guide designing advanced photocatalysts.展开更多
The strength-ductility trade-offdilemma is hard to be evaded in high-strength Mg alloys at sub-zero temperatures,especially in the Mg alloys containing a high volume fraction of precipitates.In this paper,we report an...The strength-ductility trade-offdilemma is hard to be evaded in high-strength Mg alloys at sub-zero temperatures,especially in the Mg alloys containing a high volume fraction of precipitates.In this paper,we report an enhanced strength-ductility synergy at sub-zero temperatures in an aged Mg-7.37Gd-3.1Y-0.27Zr alloy.The tensile stress-strain curves at room temperature(RT),−70℃ and−196℃ show that the strength increases monotonically with decreasing temperature,but the elongation increases first from RT to−70℃ then declines from−70℃ to−196℃.After systematic investigation of the microstructure evolutions at different deformation temperatures via synchrotron X-ray diffraction,electron backscattered diffraction(EBSD)and transmission electron microscopy(TEM),it is found that a high dislocation density with sufficient<c+a>dislocations promotes good tensile ductility at−70℃,which is attributed to the minimized critical resolved shear stress(CRSS)ratio of non-basal<c+a>to basaldislocations.In ad-dition,more shearable precipitates can further improve the ductility via lengthening the mean free path of dislocation glide.The present work demonstrates that an excellent strength-ductility synergy at sub-zero temperatures can be achieved by introducing a high dislocation density and shearable precipitates in high-strength Mg alloys.展开更多
The internal oxide precipitates were supposed to be spherical in Wagner’s original theory,while the fol-lowing research demonstrated that this assumption is an exception rather than the truth,which caused deviations ...The internal oxide precipitates were supposed to be spherical in Wagner’s original theory,while the fol-lowing research demonstrated that this assumption is an exception rather than the truth,which caused deviations in the application of this theory.In this study,the internal oxide precipitates have a needle-like and a near-spherical morphology in a Fe-9Cr ferritic and a Fe-17Cr-9Ni austenitic steels after expo-sure to 600℃ deaerated steam for 600 h,respectively.The nano-to-atomic scale characterization shows that the morphology of the internal oxide precipitates is controlled by the structure of the interfaces be-tween the metal matrix and the internal oxide,while the interface structure is mainly affected by the crystallographic structure of the two phases and their orientation relationship.In addition,the internal oxide precipitation-induced volume expansion and the outward Fe diffusion-induced volume shrink oc-cur simultaneously during the oxidation process.The stress status in the internal oxidation zone(IOZ)is the competing result of the two factors,which could dynamically affect the high-temperature oxidation.The results obtained in this study suggest that there is potential to control the distribution,morphology,and interface structure of the internal oxide precipitates by selecting appropriate base metal and internal oxide-forming element,in order to obtain better high-temperature oxidation-resistant materials.展开更多
The worn scars on Alloy 690 after the fretting corrosion testing in simulated pressurized water reactor(PWR)secondary water have been comprehensively analyzed by scanning transmission electron microscopy(STEM)and tran...The worn scars on Alloy 690 after the fretting corrosion testing in simulated pressurized water reactor(PWR)secondary water have been comprehensively analyzed by scanning transmission electron microscopy(STEM)and transmission Kikuchi diffraction(TKD).The high-quality characterization results experimentally show that the fretting wear accelerates the corrosion of Alloy 690 in two approaches.The first one is to break the integrity of the oxide scale by introducing cavities at the oxide grain boundaries.The second one is to alter the microstructure of the underneath matrix,forming a nano-grained matrix layer.The increased grain boundary density in this layer can accelerate the consumption of Cr in the near-surface matrix.The loss of oxide scale integrity and the accelerated Cr consumption are believed to contribute to the deteriorated corrosion resistance of Alloy 690 during the fretting corrosion process.展开更多
Two kinds of metal-organic frameworks(MOFs) based on Co(Ⅱ) and Fe(Ⅱ) as metal ions and trimasic acid(TMA) as organic linker were synthesized. They were used to prepare corresponding Mg H2-TM MOF(TM = Co, Fe) composi...Two kinds of metal-organic frameworks(MOFs) based on Co(Ⅱ) and Fe(Ⅱ) as metal ions and trimasic acid(TMA) as organic linker were synthesized. They were used to prepare corresponding Mg H2-TM MOF(TM = Co, Fe) composites via ball-milling. X-ray diffraction analyses show the formation of Mg2 Co and α-Fe phases in Mg H2-TMMOF composites after decomposition. Both of the well dispersed Mg2Co andα-Fe nanoparticles exhibit considerable catalytic efficiency in accelerating the sorption kinetics of Mg H2.The dehydrogenated MgH2-Fe MOF composite shows faster hydriding kinetics than the pure Mg H2 and Mg H2-CoMOF. Meanwhile, the apparent dehydrogenation activation energy(Ed) of the Mg H2-Co MOF and Mg H2-Fe MOF composites are 151.3 ± 9.4 and 142.3 ± 6.5 kJ/mol H2, both of which are lower than that of pure Mg H2(181.4 ± 9.2 kJ/mol H2). The improvement on the sorption kinetics of the Mg H2-TM MOF powders is mainly attributed to the catalytic effects of nano-sized Mg2 Co and α-Fe formed on the surface of Mg/Mg H2 particles.展开更多
Magnesium(Mg) alloys with hexagonal close-packed(HCP) structure usually have a poor ductility at room temperature. The addition of yttrium(Y) can improve the ductility of Mg alloys. To understand the underlying mechan...Magnesium(Mg) alloys with hexagonal close-packed(HCP) structure usually have a poor ductility at room temperature. The addition of yttrium(Y) can improve the ductility of Mg alloys. To understand the underlying mechanism, crystal plasticity finite element method(CPFEM) was employed to simulate the tensile deformation of a Mg-0.8 wt% Y alloy. The simulated stress–strain curve and the grain-scale slip activities were compared with an in-situ tensile test conducted in a scanning electron microscope.According to the CPFEM result, basal slip is the dominant deformation mode in the plastic deformation stage, accounting for about 50% of total strain. Prismatic slip and pyramidal a slip are responsible for about 25% and 20% of the total strain, respectively. Pyramidal c + a slip and twinning, on the other hand,accommodate much less strain.展开更多
Composition homogenization in solid solution is important for industrial alloys. In the present work, a solute homogenization model is proposed based on the chemical short-range-order tendency in Mg-Gd- based alloys. ...Composition homogenization in solid solution is important for industrial alloys. In the present work, a solute homogenization model is proposed based on the chemical short-range-order tendency in Mg-Gd- based alloys. After a calculation using the cluster-plus-glue-atom model, the stable Mg-Gd structural unit is derived, [Gd-Mg12 ]Mg6, where one solute Gd is nearest-neighbored with twelve Mg atoms to form the characteristic hcp cluster [Gd-Mg12 ] and this cluster is matched with six Mg glue atoms. Such a local unit is then mixed with [Mg-Mg12 ]Mg3, the stable unit for pure Mg. Assuming that the Gd-containing units are arranged in fcc- or bcc-like lattice points and the Mg units in their octahedral interstices, three proportions between the two units are obtained, 1:1, 2:3, and 1:3, which constitute three solute homogenization modes. The prevailing Mg-Gd-based alloys are consequently classified into three groups, respectively exemplified by GW103 K (Mg-10Gd-3Y-0.4Zr, wt%), GW83 K (Mg-SGd-3Y-0.4Zr), and GW63 K (Mg-6Gd- 3Y-0.4Zr). Mg-Gd-Y-Zr alloys were designed following the model (where Y and Zr were also added in substitution for Gd) and prepared by permanent-mould casting. According to their mechanical properties, the 1:3 alloy (Mg-5.9Gd-1.6Y-0.4Zr) shows the best comprehensive properties (ultimate tensile strength 305 MPa, yield strength 186 MPa, elongation 9.0%) in solution plus ageing state.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.展开更多
Generalized stacking-fault energies (GSFEs) of basal-plane stacking faults 11 and 12 in Mg alloys have been studied based on first-principles calculations, where 43 alloying elements were considered. It is found tha...Generalized stacking-fault energies (GSFEs) of basal-plane stacking faults 11 and 12 in Mg alloys have been studied based on first-principles calculations, where 43 alloying elements were considered. It is found that the most contributing features of alloying elements to GSFEs are bulk modulus, equilibrium volume, binding energy, atomic radius and ionization energy. Both bulk modulus and ionization energy exhibit positive relationships with GSFEs, and the others show opposite relationships. Multiple regressions have been performed to offer a quantitative prediction for basal-plane GSFEs in Mg-X systems. GSFEs, alloying effects of elements and the prediction model established within this work may provide guidelines for new Mg alloys design with better ductility.展开更多
Mg-Gd-Y-Zr alloys with high strength fall within narrow composition range.The present paper explains their composition rule by establishing the cluster-plus-glue-atom unit of Gd-containing Mg solid solution with the a...Mg-Gd-Y-Zr alloys with high strength fall within narrow composition range.The present paper explains their composition rule by establishing the cluster-plus-glue-atom unit of Gd-containing Mg solid solution with the aid of Mg matrix and Mg_(5) Gd precipitate phase.First,based on the structural homologue between Gd-containing Mg solid solution and Mg_(5) Gd precipitate phase and in combination with our previously established method for calculating the glue atoms,[Gd-Mg_(12)]Mg_(5) is obtained as the chemical unit of Gd-containing Mg solid solution.Then,seven compositions are designed using different combinations of this unit and that of pure Mg[Mg-Mg_(12)Mg3.After a systematic experimental investigation on the microstructure and mechanical property evolutions as a function of the unit proportions,it is revealed that the Mg-10.1 Gd-3.3 Y-0.9 Zr alloy,being issued from equi-proportion mixing of the two units,shows the strongest tendency of precipitation and reaches the highest strength of 374 MPa after aging.The composition and strength of this alloy are quite close to GW103 K which is well recognized for its general mechanical performance in Mg-Gd-Y-Zr system.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0701202,No.2017YFB0701500 and No.2020YFB1505901)National Natural Science Foundation of China(General Program No.51474149,52072240)+3 种基金Shanghai Science and Technology Committee(No.18511109300)Science and Technology Commission of the CMC(2019JCJQZD27300)financial support from the University of Michigan and Shanghai Jiao Tong University joint funding,China(AE604401)Science and Technology Commission of Shanghai Municipality(No.18511109302).
文摘Magnesium(Mg)alloys have shown great prospects as both structural and biomedical materials,while poor corrosion resistance limits their further application.In this work,to avoid the time-consuming and laborious experiment trial,a high-throughput computational strategy based on first-principles calculations is designed for screening corrosion-resistant binary Mg alloy with intermetallics,from both the thermodynamic and kinetic perspectives.The stable binary Mg intermetallics with low equilibrium potential difference with respect to the Mg matrix are firstly identified.Then,the hydrogen adsorption energies on the surfaces of these Mg intermetallics are calculated,and the corrosion exchange current density is further calculated by a hydrogen evolution reaction(HER)kinetic model.Several intermetallics,e.g.Y_(3)Mg,Y_(2)Mg and La_(5)Mg,are identified to be promising intermetallics which might effectively hinder the cathodic HER.Furthermore,machine learning(ML)models are developed to predict Mg intermetallics with proper hydrogen adsorption energy employing work function(W_(f))and weighted first ionization energy(WFIE).The generalization of the ML models is tested on five new binary Mg intermetallics with the average root mean square error(RMSE)of 0.11 eV.This study not only predicts some promising binary Mg intermetallics which may suppress the galvanic corrosion,but also provides a high-throughput screening strategy and ML models for the design of corrosion-resistant alloy,which can be extended to ternary Mg alloys or other alloy systems.
基金financially supported by the National Natural Science Foundation of China (Nos. 51671127, 51631006, 51971168)sponsored by the Shanghai Rising-Star Programsupported by the United States Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02–06CH11357
文摘Mg-Y cast alloy shows excellent ductility(elongation to failure>15%)compared with pure Mg and commercial Mg cast alloys.By monitoring the microstructure evolution during an in situ tensile test of a Mg-2.5 wt%Y alloy,we identify the activation of prismatic<c>slip,which is rare in Mg.Synchrotron X-ray micro-beam Laue diffraction(μ-Laue)and transmission electron microscopy revealed the morphology of prismatic<c>slip bands and individual<c>dislocations.Density functional theory and molecular dynamics calculations indicate that solute Y can significantly reduce the stacking fault energy(SFE)along<c>direction on prismatic plane in Mg lattice and thus facilitate the nucleation of<c>dislocations during deformation.The presence of free<c>dislocations in the Mg lattice can also lead to nucleation of{10–12}twins even under unfavorable geometric conditions.
文摘Background: Double-lumen endotracheal (DLT) is commonly used for one-lung ventilation and lung separation during thoracic surgery. There are case reports of medically induced laryngeal granulomas, mainly in patients after single-lumen endotracheal (SLT) tube intubation and tracheotomy, and giant granulomas of the vocal cords due to double-lumen bronchial tube insertion have rarely been reported. Case presentation: A 49-year-old female patient underwent single-port thoracoscopy after DLT intubation as well as a wedge resection of the lower lobe of the left lung, which caused giant vocal process granulomas (VPGs) postoperatively. Based on a retrospective analysis of the general condition, current medical history, past medical history, and visual laryngoscopic observation of the vocal folds tissue, which ruled out preoperative vocal fold granuloma formation, we hypothesized that double-lumen bronchial catheter intubation may have been the primary cause of her vocal fold granuloma formation. Conclusions: Giant granuloma of the vocal folds after DLT insertion is a rare postoperative complication;therefore, if DLT intubation is to be performed, the anesthesiologist should choose an appropriate intubation plan and deal with it promptly to avoid the risk factors to ensure that the patient’s perioperative period is safe and smooth. In addition, if postoperative complications are encountered, they should be followed up and observed on time.
基金financially supported by Shanghai Rising-Star Program (20QA1405000)the National Natural Science Foundation of China (nos.U2032124 and 82204850)。
文摘Molecule hydrogen(H_(2)) has been used to suppress tumor growth. To employ the H_(2) therapy, it is necessary to use a proper agent for continuous generation of H_(2). As a biodegradable metal, magnesium(Mg) generates H_(2) in an aqueous environment, but the H_(2) release rate is still too low. Here, we design a Mg-Al-Ca(AX) alloy that degrades very rapidly due to the presence of a secondary phase Al_(2)Ca. Having a reduction potential much higher than Mg and any other Mg-based secondary phases, Al_(2)Ca accelerates the corrosion of the Mg matrix by a micro-galvanic process. Al_(2)Ca also enhances the strength and ductility of the AX alloy. AX alloy rods show better anti-tumor efficacy than pure Mg rods in vivo. Moreover, implanted AX alloy rods can be heated under an alternating magnetic field to suppress large-size tumors.This work suggests that the H_(2) therapy using highly degradable Mg alloys may provide an effective cancer treatment.
基金supported by National Natural Science Foundation of China(No.51701121,No.51825101)Shanghai Sailing Program(No.17YF1408800)+2 种基金Laboratory of Intense Dynamic Loading and Effect Foundation of China(No.IDEL1908)Startup Fund for Youngman Research at SJTU(No.18×100040022)Science and Technology Commission of Shanghai Municipality(No.18511109302).
文摘The local deformation behavior and dynamic recrystallization of a shock compressed Mg-1Zn alloy was investigated through EBSD and TEM.Since dislocation slipping and twinning were locally suppressed during high strain-rate deformation,a more flexible kinking deformation was activated to adjusted local orientation and facilitate slipping and twinning within the kinks.Meanwhile,due to the slow heat dissipation that resulted in a local temperature elevating,the kink bands were evolved into deformation bands with recrystallized nano-grains.Such a finding provides a new perspective for kinking-facilitated nanocrystallization in Mg alloys and other anisotropic metallic materials.
基金supported by Shanghai Science and Technology Committee (No.18511109300)Science and Technology Commission of the CMC (2019JCJQZD27300)+1 种基金Foundation from Shanghai Jiao Tong University (AF0500132,AF0500149)Funding from Center of Hydrogen Science of Shanghai Jiao Tong University。
文摘Mathematical models were proposed to clarify the effect of alloying on corrosion of magnesium alloys based on film-free and film-covered status. The models are applicable to explain the “barrier effect” by cathodes and the “analogous Hall-Petch relationship” between corrosion rates and grain size. The slope of corrosion rates versus alloying content is determined by the dissolution ability of film-free substrate and the hindering effects by corrosion product film. Designing strategy for corrosion-resistant Mg alloys is established.
基金This work was co-funded by,The National Key Research and Development Program of China(NO.2016YFB0301002)and General Motors Global Research and Development.
文摘Few studies were reported on the phases'relationships of AE44(Mg-4.0Al-4.1RE-0.3Mn,wt.%)and its composites.In this work,AE44 alloy and Saffil(6-Al2O3)/AE44 Metal matrix composite(MMC)were both prepared by slow shot high pressure die casting(SS-HPDC)technology and their phase constitutions were all studied in detail using experimental techniques combined with CALPHAD(Calculation of Phase Diagram)modeling.The results revealed that the alloy consists of the a-Mg matrix,A1hRE3 intermetallic phase,and one trace phase AI3RE,while the composite contains five major phases:a-Mg,5-AI2O3,AI3RE,MgO and Mg2Si.and two trace phases of A12RE and AI11RE3,respectively.A1hRE3 is partly derived from ALRE,while A13RE is a product of the peritectoid reaction between the two precipitates.The presence of MgO and Mg2Si is due to the interfacial reaction between the SiO2 binder in the fiber preforms and the molten magnesium during infiltration.The use of SiO2 binder in the preform manufacturing was limited/minimized to reduce the MgO formation in the MMC casting process,which can be detrimental to the fatigue performance of the MMC materials.
基金The authors gratefully acknowledge the financial support of the projects from the National Natural Science Foundation of China(Nos.51631006,51671127,51825101)。
文摘Alloying elements can drastically alter the deformation behavior of Mg.In the present work,Visco-Plastic Self-Consistent(VPSC)modeling was employed to investigate the effect of alloying elements on Mg’s tensile behavior,in particular the relative activity of different slip and twinning modes.Mg-0.47 wt.%Ca,Mg-2 wt.%Nd,and AZ31 extruded alloys were deformed by micro-tensile tests in a scanning electron microscope(SEM).Texture and grain size measured by electron backscatter diffraction(EBSD)were used as the input for VPSC.After parameter optimization,the VPSC model successfully reproduced the stress-strain curve of each alloy.Simulation results indicate that the slip/twinning activity in the three alloys are different.Mg-0.47 wt.%Ca shows strong extrusion texture,and prismatic slip was quite active during its tensile deformation.In contrast,Mg-2 wt.%Nd shows weak extrusion texture,and basal slip was dominant.This alloy also developed more twinning activity than the other two alloys.AZ31 shows strong extrusion texture similar as Mg-0.47 wt.%Ca,but prismatic slip was less active in it.The slip/twinning activity revealed by the VPSC model can explain the difference in the tensile behavior of the three alloys.
基金financially the Major Science and Technology projects in Qinghai province(2018GX-A1)Shanghai Science and Technology Committee(No.18511109302)+1 种基金The National Key R&D Program(No.2016YFB0301002)the Ministry of Science and Technology of Chinaco-funded by the National Natural Science Foundation of China(No.51825101)。
文摘The 3D visualization of the porosity in high-pressure die casting(HPDC)Mg alloys AZ91D and Mg4Ce2Al0.5Mn(EA42)was investigated by X-ray computed tomography.It was demonstrated that the volumetric porosity at the near-gate location for alloy EA42 was significantly higher than that far from the gate location.This difference resulted from the low valid time during intensified casting pressure conditions.Specimens of alloy EA42 exhibited a narrow pore distribution in the side view(~0.5 mm)compared to the wide distribution(~1.8 mm)of alloy AZ91D,which was mainly attributed to the formation mechanism of the defect band.The formation of microporosity in the defect band of alloy EA42 was inhibited because of the significant latent heat released by a large amount of the Al11Ce3phase segregated in the defect band during solidification.Additionally,an effective estimator(Z-Propagation)was introduced,which is proposed to predict the projected area fraction of the porosity(f)involved during tensile failure with better effectiveness compared with traditional methods based on the actual fractured surface.By coupling the Z-Propagation method with the critical local strain model,the logarithmic fracture strain and true fracture stress of the specimens were predicted within 3.03%and 1.65%of the absolute value of the average relative error(AARE),respectively.
基金financially supported by National Natural Science Foundation of China(No.51701121,No.51825101)Shanghai Sailing Program(17YF1408800)+2 种基金Science and Technology Commission of Shanghai Municipality(No.18511109302)Qinghai Provincial Science and Technology Key Program(No.2018-GX-A1)Startup Fund for Youngman Research at SJTU(No.18X100040022)
文摘Static recrystallization of a high strain rate compressed Mg-1 Zn(wt.%)alloy was investigated using electron backscattered diffraction(EBSD).A novel 53°1010 structure was observed in the as-deformed alloy,which showed a{1012}-{1012}double twin relationship with the matrix.When the as-deformed alloy was annealed at 200°C,the{1011}compression twins and{1011}-{1012}double twins showed a higher priority to recrystallize.In addition,the coarse{1012}tension twins and their inner double twins were preferentially to recrystallize,while the lenticular tension twins had little impact on the recrystallization.Therefore,obtaining more compression twins or coarse twins instead of lenticular tension twins can be an effective approach to manipulate recrystallization process in deformed Mg alloys.
基金The authors thank Professor Yongxiang Hu for the ns-LSP experiment on Mg-3Gd alloy and his useful discussion.The research was supported by the National Key R&D Program of China(2017YFA0303700)the National Natural Science Foundation of China(NSFC)(11574208).
基金supported by the National Science Foundation of China (21875137, 51521004, and 51420105009)Innovation Program of Shanghai Municipal Education Commission (Project No. 2019-01-07-00-02-E00069)+1 种基金the 111 Project (Project No. B16032)the fund from Center of Hydrogen Science and Joint Research Center for Clean Energy Materials at Shanghai Jiao Tong University for financial supports。
文摘Semiconductor photocatalysis, as a key part of solar energy utilization, has far-reaching implications for industrial, agricultural, and commercial development. Lack of understanding of the catalyst evolution and the reaction mechanism is a critical obstacle for designing efficient and stable photocatalysts. This review summarizes the recent progress of in-situ exploring the dynamic behavior of catalyst materials and reaction intermediates. Semiconductor photocatalytic processes and two major classes of in-situ techniques that include microscopic imaging and spectroscopic characterization are presented. Finally, problems and challenges in in-situ characterization are proposed, geared toward developing more advanced in-situ techniques and monitoring more accurate and realistic reaction processes, to guide designing advanced photocatalysts.
基金We acknowledge Prof.Jian Wang from the University of Nebraska-Lincoln for insightful discussion.This work is financially supported by the National Key R&D Program of China(No.2021YFB3501005)the Space Utilization System of China Manned Space Engineering(No.KJZ-YY-WCL04)+1 种基金the Natural Science Foundation of Shanghai(No.23ZR1431100)the National Natural Science Foundation of China(No.51825101).Shanghai Syn-chrotron Radiation Facility is acknowledged for supporting the syn-chrotron high energy X-ray diffraction experiments at Beam Line No.BL14B1.
文摘The strength-ductility trade-offdilemma is hard to be evaded in high-strength Mg alloys at sub-zero temperatures,especially in the Mg alloys containing a high volume fraction of precipitates.In this paper,we report an enhanced strength-ductility synergy at sub-zero temperatures in an aged Mg-7.37Gd-3.1Y-0.27Zr alloy.The tensile stress-strain curves at room temperature(RT),−70℃ and−196℃ show that the strength increases monotonically with decreasing temperature,but the elongation increases first from RT to−70℃ then declines from−70℃ to−196℃.After systematic investigation of the microstructure evolutions at different deformation temperatures via synchrotron X-ray diffraction,electron backscattered diffraction(EBSD)and transmission electron microscopy(TEM),it is found that a high dislocation density with sufficient<c+a>dislocations promotes good tensile ductility at−70℃,which is attributed to the minimized critical resolved shear stress(CRSS)ratio of non-basal<c+a>to basaldislocations.In ad-dition,more shearable precipitates can further improve the ductility via lengthening the mean free path of dislocation glide.The present work demonstrates that an excellent strength-ductility synergy at sub-zero temperatures can be achieved by introducing a high dislocation density and shearable precipitates in high-strength Mg alloys.
基金This work was financially supported by National Key Re-search and Development Program of China(No.2018YFE0116200)Shanghai Pujiang Program(No.21PJ1406400)+1 种基金EPSRC(Nos.EP/K040375/1,EP/N010868/1,and EP/R009392/1)Prof.Lefu Zhang is acknowledged for providing the samples used in this study.In-strumental Analysis Center of SJTU is also gratefully acknowledged.The atom probe facilities at the University of Oxford are funded by the EPSRC(No.EP/M022803/1).
文摘The internal oxide precipitates were supposed to be spherical in Wagner’s original theory,while the fol-lowing research demonstrated that this assumption is an exception rather than the truth,which caused deviations in the application of this theory.In this study,the internal oxide precipitates have a needle-like and a near-spherical morphology in a Fe-9Cr ferritic and a Fe-17Cr-9Ni austenitic steels after expo-sure to 600℃ deaerated steam for 600 h,respectively.The nano-to-atomic scale characterization shows that the morphology of the internal oxide precipitates is controlled by the structure of the interfaces be-tween the metal matrix and the internal oxide,while the interface structure is mainly affected by the crystallographic structure of the two phases and their orientation relationship.In addition,the internal oxide precipitation-induced volume expansion and the outward Fe diffusion-induced volume shrink oc-cur simultaneously during the oxidation process.The stress status in the internal oxidation zone(IOZ)is the competing result of the two factors,which could dynamically affect the high-temperature oxidation.The results obtained in this study suggest that there is potential to control the distribution,morphology,and interface structure of the internal oxide precipitates by selecting appropriate base metal and internal oxide-forming element,in order to obtain better high-temperature oxidation-resistant materials.
基金Shanghai Pujiang Program(No.21PJ1406400)is acknowledged for funding this research.
文摘The worn scars on Alloy 690 after the fretting corrosion testing in simulated pressurized water reactor(PWR)secondary water have been comprehensively analyzed by scanning transmission electron microscopy(STEM)and transmission Kikuchi diffraction(TKD).The high-quality characterization results experimentally show that the fretting wear accelerates the corrosion of Alloy 690 in two approaches.The first one is to break the integrity of the oxide scale by introducing cavities at the oxide grain boundaries.The second one is to alter the microstructure of the underneath matrix,forming a nano-grained matrix layer.The increased grain boundary density in this layer can accelerate the consumption of Cr in the near-surface matrix.The loss of oxide scale integrity and the accelerated Cr consumption are believed to contribute to the deteriorated corrosion resistance of Alloy 690 during the fretting corrosion process.
基金supported financially by the National Natural Science Foundation of China (No. 51771112)the National Key Research & Development Project (No. 2018YFB1502104)+1 种基金the Shanghai Science and Technology Commission (No. 14JC1491600)the Shanghai Education Commission “Shuguang” Scholar Project (No. 16SG08)
文摘Two kinds of metal-organic frameworks(MOFs) based on Co(Ⅱ) and Fe(Ⅱ) as metal ions and trimasic acid(TMA) as organic linker were synthesized. They were used to prepare corresponding Mg H2-TM MOF(TM = Co, Fe) composites via ball-milling. X-ray diffraction analyses show the formation of Mg2 Co and α-Fe phases in Mg H2-TMMOF composites after decomposition. Both of the well dispersed Mg2Co andα-Fe nanoparticles exhibit considerable catalytic efficiency in accelerating the sorption kinetics of Mg H2.The dehydrogenated MgH2-Fe MOF composite shows faster hydriding kinetics than the pure Mg H2 and Mg H2-CoMOF. Meanwhile, the apparent dehydrogenation activation energy(Ed) of the Mg H2-Co MOF and Mg H2-Fe MOF composites are 151.3 ± 9.4 and 142.3 ± 6.5 kJ/mol H2, both of which are lower than that of pure Mg H2(181.4 ± 9.2 kJ/mol H2). The improvement on the sorption kinetics of the Mg H2-TM MOF powders is mainly attributed to the catalytic effects of nano-sized Mg2 Co and α-Fe formed on the surface of Mg/Mg H2 particles.
基金financially supported by the National Natural Science Foundation of China (Nos. 51631006, 51671127 and 51825101)
文摘Magnesium(Mg) alloys with hexagonal close-packed(HCP) structure usually have a poor ductility at room temperature. The addition of yttrium(Y) can improve the ductility of Mg alloys. To understand the underlying mechanism, crystal plasticity finite element method(CPFEM) was employed to simulate the tensile deformation of a Mg-0.8 wt% Y alloy. The simulated stress–strain curve and the grain-scale slip activities were compared with an in-situ tensile test conducted in a scanning electron microscope.According to the CPFEM result, basal slip is the dominant deformation mode in the plastic deformation stage, accounting for about 50% of total strain. Prismatic slip and pyramidal a slip are responsible for about 25% and 20% of the total strain, respectively. Pyramidal c + a slip and twinning, on the other hand,accommodate much less strain.
基金supported financially by the National Key Research and Development Program of China (No. 2016YFB0701201)the Natural Science Foundation of China (No. 11674045)
文摘Composition homogenization in solid solution is important for industrial alloys. In the present work, a solute homogenization model is proposed based on the chemical short-range-order tendency in Mg-Gd- based alloys. After a calculation using the cluster-plus-glue-atom model, the stable Mg-Gd structural unit is derived, [Gd-Mg12 ]Mg6, where one solute Gd is nearest-neighbored with twelve Mg atoms to form the characteristic hcp cluster [Gd-Mg12 ] and this cluster is matched with six Mg glue atoms. Such a local unit is then mixed with [Mg-Mg12 ]Mg3, the stable unit for pure Mg. Assuming that the Gd-containing units are arranged in fcc- or bcc-like lattice points and the Mg units in their octahedral interstices, three proportions between the two units are obtained, 1:1, 2:3, and 1:3, which constitute three solute homogenization modes. The prevailing Mg-Gd-based alloys are consequently classified into three groups, respectively exemplified by GW103 K (Mg-10Gd-3Y-0.4Zr, wt%), GW83 K (Mg-SGd-3Y-0.4Zr), and GW63 K (Mg-6Gd- 3Y-0.4Zr). Mg-Gd-Y-Zr alloys were designed following the model (where Y and Zr were also added in substitution for Gd) and prepared by permanent-mould casting. According to their mechanical properties, the 1:3 alloy (Mg-5.9Gd-1.6Y-0.4Zr) shows the best comprehensive properties (ultimate tensile strength 305 MPa, yield strength 186 MPa, elongation 9.0%) in solution plus ageing state.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0701202)the National Natural Science Foundation of China(General Program No.51474149 and Key Program No.51631006)
文摘Generalized stacking-fault energies (GSFEs) of basal-plane stacking faults 11 and 12 in Mg alloys have been studied based on first-principles calculations, where 43 alloying elements were considered. It is found that the most contributing features of alloying elements to GSFEs are bulk modulus, equilibrium volume, binding energy, atomic radius and ionization energy. Both bulk modulus and ionization energy exhibit positive relationships with GSFEs, and the others show opposite relationships. Multiple regressions have been performed to offer a quantitative prediction for basal-plane GSFEs in Mg-X systems. GSFEs, alloying effects of elements and the prediction model established within this work may provide guidelines for new Mg alloys design with better ductility.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0701201)the Natural Science Foundation of China(No.11674045)。
文摘Mg-Gd-Y-Zr alloys with high strength fall within narrow composition range.The present paper explains their composition rule by establishing the cluster-plus-glue-atom unit of Gd-containing Mg solid solution with the aid of Mg matrix and Mg_(5) Gd precipitate phase.First,based on the structural homologue between Gd-containing Mg solid solution and Mg_(5) Gd precipitate phase and in combination with our previously established method for calculating the glue atoms,[Gd-Mg_(12)]Mg_(5) is obtained as the chemical unit of Gd-containing Mg solid solution.Then,seven compositions are designed using different combinations of this unit and that of pure Mg[Mg-Mg_(12)Mg3.After a systematic experimental investigation on the microstructure and mechanical property evolutions as a function of the unit proportions,it is revealed that the Mg-10.1 Gd-3.3 Y-0.9 Zr alloy,being issued from equi-proportion mixing of the two units,shows the strongest tendency of precipitation and reaches the highest strength of 374 MPa after aging.The composition and strength of this alloy are quite close to GW103 K which is well recognized for its general mechanical performance in Mg-Gd-Y-Zr system.