Effect of Zn addition on microstructure and mechanical properties of cast Mg-Gd-Y-Zr alloys

The effects of Zn addition on the microstructure and mechanical properties of Mg.10Gd.3Y.0.6Zr(wt.%)alloys in the as-cast,solution-treated,and peak-aged conditions were investigated.Experimental results reveal that the microstructure of the as-cast alloy without Zn consists ofα-Mg and Mg24(Gd,Y)5 phases,and the alloy with 0.5 wt.%Zn consists ofα-Mg,(Mg,Zn)3(Gd,Y)and Mg24(Gd,Y,Zn)5 phases.With the addition of Zn increasing to 1 wt.%,the Mg24(Gd,Y,Zn)5 phase disappears and some needle-like stacking faults distribute along the grain boundaries.Moreover,the 18R long-period stacking ordered(LPSO)phase is observed in the as-cast alloy with 2 wt.%Zn.After solution treatment,the Mg24(Gd,Y)5 and Mg24(Gd,Y,Zn)5 eutectic phases are completely dissolved,and the(Mg,Zn)3(Gd,Y)phase,needle-like stacking faults and 18R LPSO phase all transform into 14H LPSO phase.Both the suitable volume fraction of 14H LPSO phases and the fine ellipsoidal-shapedβ′phases make the peak-aged alloy with 0.5 wt.%Zn exhibit excellent comprehensive mechanical properties and the UTS,YS and elongation are 338 MPa,201 MPa and 6.8%,respectively.

Phase-field crystal simulation of evolution of liquid pools in grain boundary pre-melting regions

Pre-melting is a phenomenon that below the melting point the liquid-like structure appears at the grainboundary while the grain interior remains a crystal structure. The phase-field crystal method was employed to investigate the early evolution of the liquid pools in pre-melting regions, mainly involving four structural transformations: solid-solid state → small droplet → large liquid pool → homogeneous liquid melting. The microscopic morphology and free energy variation with different average atomic densities demonstrate that the average atomic density is sensitive to the morphological characteristics of liquid pools. Both two-dimensional and three-dimensional simulation results show that the amplitude reduction of order parameters can promote the order-disorder transition of grain boundaries, causing pre-melting in the edge dislocation aggregation. The relationship between the average atomic density and the width of the liquid pools is verified from thermodynamics, which provides a prerequisite for the application of high-temperature strain in the later stage to some extent.

Effect of Al addition on microstructure and mechanical properties of Mg-Gd-Zn alloys

The microstructure evolution and mechanical properties of Mg−15.3Gd−1Zn alloys with different Al contents(0,0.4,0.7 and 1.0 wt.%)were investigated.Microstructural analysis indicates that the addition of 0.4 wt.%Al facilitates the formation of 18R-LPSO phase(Mg12Gd(Al,Zn))in the Mg−Gd−Zn alloy.The contents of Al11Gd3 and Al2Gd increase with the increase of Al content,while the content of(Mg,Zn)_(3)Gd decreases.After homogenization treatment,(Mg,Zn)_(3)Gd,18R-LPSO and some Al11Gd3 phases are transformed into the high-temperature stable 14H-LPSO phases.The particulate Al−Gd phases can stimulate the nucleation of dynamic recrystallization by the particle simulated nucleation(PSN)mechanism.The tensile strength of the as-rolled alloys is improved remarkably due to the grain refinement and the fiber-like reinforcement of LPSO phase.The precipitation of theβ′phase in the peak-aged alloys can significantly improve the strength.The peak-aged alloy containing 0.4 wt.%Al achieves excellent mechanical properties and the UTS,YS and elongation are 458 MPa,375 MPa and 6.2%,respectively.

Application of AI and IoT in Clinical Medicine:Summary and Challenges

The application of artificial intelligence(AI)technology in the medical field has experienced a long history of development.In turn,some long-standing points and challenges in the medical field have also prompted diverse research teams to continue to explore AI in depth.With the development of advanced technologies such as the Internet of Things(IoT),cloud computing,big data,and 5G mobile networks,AI technology has been more widely adopted in the medical field.In addition,the in-depth integration of AI and IoT technology enables the gradual improvement of medical diagnosis and treatment capabilities so as to provide services to the public in a more effective way.In this work,we examine the technical basis of IoT,cloud computing,big data analysis and machine learning involved in clinical medicine,combined with concepts of specific algorithms such as activity recognition,behavior recognition,anomaly detection,assistant decision-making system,to describe the scenario-based applications of remote diagnosis and treatment collaboration,neonatal intensive care unit,cardiology intensive care unit,emergency first aid,venous thromboembolism,monitoring nursing,image-assisted diagnosis,etc.We also systematically summarize the application of AI and IoT in clinical medicine,analyze the main challenges thereof,and comment on the trends and future developments in this field.

Microalloying Effect of Sn on Phase Transformation During Heat Treatment in Mg–Y–Zn–Zr Alloys

The microstructure and mechanical properties of the as-cast and heat-treated Mg-4.6 Y-2.5 Zn-0.6 Zr-x Sn(x = 0, 0.2 and0.5 wt%) alloys were investigated in this work. The results showed that the eutectics have been refined with 0.2% Sn addition and it has no effect on the phase category of the alloys. However, Sn3 Y5 phase was found in 0.5% Sn-added alloy.After heat treatment at 520 °C, the transformation of the long-period stacking ordered(LPSO) phase takes place in the Mg-Y-Zn-Zr alloy, but the transition is not completed in the alloys containing Sn. In addition, during the heat treatment, the mechanical properties of Sn-free alloys are significantly improved, and the strength of alloys containing Sn does not change much. Through observation and analysis of the microstructure and mechanical properties, it is found that Sn addition hinders the process of a0-Mg ? a-Mg ? 14 H and the process is the key to the transition of 18 H-LPSO to 14 H-LPSO.

Microscopic Phase-Field Simulation for the Influence of Interatomic Potential on the Precipitation Process of Ni_(75)Al_(14)Mo_(11) Alloy

Abstract The process of γ＇ phase precipitating from Ni75Al14MO11 is studied by a computational simulation technique based on microscopic phase-field kinetics model. We studied the phase transformation with the purpose of clarifying the influence of the nearest interatomic potential V Ni-Al （the nearest interatomic potential） on the precipitation process of γ＇ phase. The result demonstrates that there are two kinds of ordered phases, respective Llo and L12 in the early stage, and Llo phase transforms into L12 phase subsequently. For L12 phase, Ni atoms mainly occupy α site （face center positions）, while Al and Mo atoms occupy fl sites （the vertex positions）. When VNi-Al is increased by 10 MeV, the occupation probability of Ni atoms on α sites and Al atoms on β sites are enhanced. Enhanced VNi-Al facilitates clustering and ordering of Al atom, which promotes the formation of the γ＇ phase. At last, the simulation result was discussed by employing the thermodynamic stability.

The sirtuin family in health and disease

Sirtuins(SIRTs)are nicotine adenine dinucleotide(+)-dependent histone deacetylases regulating critical signaling pathways in prokaryotes and eukaryotes,and are involved in numerous biological processes.Currently,seven mammalian homologs of yeast Sir2 named SIRT1 to SIRT7 have been identified.Increasing evidence has suggested the vital roles of seven members of the SIRT family in health and disease conditions.Notably,this protein family plays a variety of important roles in cellular biology such as inflammation,metabolism,oxidative stress,and apoptosis,etc.,thus,it is considered a potential therapeutic target for different kinds of pathologies including cancer,cardiovascular disease,respiratory disease,and other conditions.Moreover,identification of SIRT modulators and exploring the functions of these different modulators have prompted increased efforts to discover new small molecules,which can modify SIRT activity.Furthermore,several randomized controlled trials have indicated that different interventions might affect the expression of SIRT protein in human samples,and supplementation of SIRT modulators might have diverse impact on physiological function in different participants.In this review,we introduce the history and structure of the SIRT protein family,discuss the molecular mechanisms and biological functions of seven members of the SIRT protein family,elaborate on the regulatory roles of SIRTs in human disease,summarize SIRT inhibitors and activators,and review related clinical studies.

Global Pediatric Pulmonology Alliance recommendation to strengthen prevention of pediatric seasonal influenza under COVID-19 pandemic

The World Health Organization(WHO)announced COVID-19 as a global pandemic in March of 2020[1].The COVID-19 pandemic may persist for a long period of time.Global prevention and control becomes a complex and challenging task,and such efforts should be sustained.Although general measures,such as social distancing,face masks,respiratory hygiene and hand sanitization,will bear fruits for decreasing spread of other respiratory illnesses including influenza,the specific prevention through vaccination is a key focus especially in the upcoming winter and spring seasons[2].

Phase-field simulation of tip splitting in dendritic growth of Fe-C alloy

Two types of dendrite tip splitting including dendrite orientation transition and twinned-like dendrites in Fe-C alloys were investigated by phase-field method. In equiaxed growth, the possible dendrite growth directions and the effect of supersaturation on tip splitting were discussed; the dendrite orientation transition was observed, and it was found that the orientation regions of anisotropy parameters were reduced from three to two with increasing the supersaturation, which was due to the effect of interracial anisotropy controlled by the solute in front of S/L interface changing with the increase of supersaturation. In directional solidification, it was found that the twinned like dendrites were formed with the fixed anisotropy couples and no seaweed dendrites were observed; these were concluded from the results of competition between process anisotropy and inherent anisotropy. The formation process of twinned-like dendrite was investigated by tip splitting phenomenon, which was related to the chan ges of dendrite tips growth velocity. Then, the critical speed of tips splitting and solute concentration of twinned-like dendrites were investigated, and a new type of microsegregation in Fe-C alloys was proposed to supplement the dendrite growth theories.

Phase-Field Lattice-Boltzmann Study for α-Mg Dendrite Growth of Mg-5wt%Zn Alloy with Forced Convection

Melt flow can significantly change the transport of heat and solute,dendrite growth.In this work,a phase-field lattice-Boltzmann model was developed to studyα-Mg dendrite growth of Mg-5wt%Zn alloy with forced convection.Results show that the existence of forced convection and overlap of thermal and solute fields makes thermal and solute fields distribution nonuniform.Thus,the symmetry of dendrite morphology is destroyed.The solid temperature and concentration of the downstream dendrite tip front with forced convection are higher than that without forced convection,while the concentration of the upstream dendrite tip front is lower.The solute transport through melt flow will be hindered by developed sidebranching.With flow velocity increase,the upstream temperature gradient and thickness of the downstream solute enrichment layer increase gradually,while the downstream temperature gradient and thickness of the upstream solute enrichment layer decrease gradually.Meanwhile,the upstream dendrite tip velocity will increase gradually,while the downstream dendrite tip velocity will decrease at first and then unchanged.This study is helpful to establish the relationship betweenα-Mg dendrite growth and melt flow,which is beneficial to understand the role of melt flow on dendrite morphologies.