砂型铸造Mg-9Gd-3Y-0.5Zr合金的线收缩

研究铸件几何特征对砂型铸造Mg-9Gd-3Y-0.5Zr(VW93)合金线收缩的影响。利用3D扫描仪精确提取自由收缩和受阻收缩砂铸件的尺寸,并用于计算收缩系数。引入砂芯体积与铸件包络体积之比(γ)量化砂芯对铸件收缩的约束程度。通过分析自由收缩系数的统计分布和受阻收缩系数随γ的变化规律发现,VW93合金的自由收缩系数为1.96%,受阻收缩系数随γ的增大而线性减小,此关系为根据铸件几何结构预测VW93合金收缩率提供支持。

Research trends of machine learning in traditional medicine:a big-data based tenyear bibliometric analysis

Background:With the rapid development of the world’s technology,the connection and integration between traditional medicine and modern machine learning technology are increasingly close.In this study,we aimed to analyze publications on machine learning in traditional medicine by using bibliometric methods and explore global trends in the field.Methods:Relevant research on machine learning in traditional medicine extracted from the Web of Science Core Collection database.Bibliometric analysis and visualization were performed using the Bibliometrix package in R software.Global trends,source journals,authorship,and thematic keywords analysis were performed in this study.Results:From 2012 to 2022,a total of 282 publications on machine learning in traditional medicine were identified and analyzed.The average annual growth rate of the publications was 13.35%.China had the largest contribution in this field(53.9%),followed by the United States(32.6%).IEEE Access had the largest number of published articles,with a total of 15 articles.Calvin Yu-Chian Chen,Xiao-juan Hu and Jue Wang were the main researchers in this field.Shanghai University of Traditional Chinese Medicine and University of California,San Francisco were the main research institutions.Conclusion:This study provides information on research trends in machine learning in traditional medicine to better understand research hotspots and future developments in this field.According to current global trends,the number of publications in this field will gradually increase.China currently dominated the field.Applied research of machine learning techniques may be the next hot topic in this field and deserves further attention.

Microstructure and corrosion behavior of as-homogenized and as-extruded Mg-xLi-3Al-2Zn-0.5Y alloys(x=4,8,12)

The microstructure and corrosion behavior of the as-homogenized and as-extruded Mg-xLi-3Al-2Zn-0.5Y alloys(x=4,8,12,wt.%)were studied.The results show that as the Li content increases from 4%to 12%,the matrix transfers from singleα-Mg phase,(α-Mg+β-Li)dual phase to singleβ-Li phase.A mixed corrosion feature of intergranular corrosion and pitting corrosion occurs in the Mg-4Li-3Al-2Zn-0.5Y and Mg-12Li-3Al-2Zn-0.5Y alloys.The former is related to the precipitated AlLi phase along the grain boundaries,and the latter is related to the high potential difference between the second phase and the matrix.The corrosion resistance of the as-extruded alloys is better than that of the as-homogenized alloys.The superior corrosion resistance of the as-extruded Mg-8Li-3Al-2Zn-0.5Y alloy with the lowest corrosion rate(P_(W)=(0.63±0.26)mm/a)is attributed to the more uniform distribution of second phases,the protectiveα-Mg phase via sacrificing theβ-Li phase and the relatively integrated oxide film.

Microstructure and mechanical properties of as-cast and solid solution treated Mg-8Li-xAl-yZn alloys

The effects of Al/Zn ratio(mass ratio) on microstructure and mechanical properties of the Mg-8 Li alloy were investigated. The results indicate that in the as-cast Mg-8Li-xAl-yZn(x+y=5) alloys(LAZ alloys), when the Al/Zn ratio is 1:4 and 2:3, the secondary phases are mainly AlLi and MgLiZn phases;when the Al/Zn ratio is 3:2 and 4:1, the secondary phases are mainly AlLi and MgLi2Al phases. The decomposition temperature of MgLiZn phase is about 300 ℃ and the decomposition temperatures of AlLi phase and MgLi2 Al phase are higher(~350 ℃). Solid solution strengthening is the main factor for the improvement of strength of Mg-8Li-xAl-yZn alloys. The Mg-8 Li-3 Al-2 Zn alloy after solution treatment at 350 ℃ for 4 h has the best comprehensive mechanical properties(yield strength of 272.5 MPa, ultimate tensile strength of 315.0 MPa and elongation of 3.4%) among the studied as-cast and solid solution treated Mg-8Li-xAl-yZn alloys.

Microstructure and mechanical properties of as-cast Mg-8Li-xZn-yGd(x=1,2,3,4;y=1,2) alloys

The as-cast Mg-8 Li-xZn-yGd(x=1 2, 3,4;y=1,2;wt.%)alloys were prepared in a vacuum induction furnace and their microstructure and mechanical properties were investigated. The results show that the increase of Zn content results in the volume fraction of W-phase(Mg3 Zn3 Gd2) increasing while that of Mg3 Gd phase decreasing. The strength of Mg-8 Li-xZn-1 Gd alloys is improved with the increase of Zn content,which is ascribed to the second phase strengthening of fine strip-like W-phase and the solid solution strengthening of Zn element.For Mg-8 Li-4 Zn-yGd alloys,the increase of Gd content leads to the appearance of coarse and discontinuous net-like W-phase, which decreases the strength. The Mg-8 Li-4 Zn-1 Gd alloy exhibits an optimum comprehensive performance with the yield strength, ultimate tensile strength and elongation of 154.7 MPa, 197.0 MPa and 12.4%, respectively. In addition,the aging behavior of the typical alloys was also investigated.

Effects of Li content on microstructure and mechanical properties of as-cast Mg-xLi-3Al-2Zn-0.5Y alloys

The effects of Li content on the microstructure and mechanical properties of the as-cast Mg−xLi−3Al−2Zn−0.5Y(LAZx32-0.5Y)alloys were investigated by XRD,SEM,TEM,hardness tester and universal testing machine.The results show that the matrix of the alloy transforms fromα-Mg toα-Mg+β-Li and then toβ-Li when the Li content increases from 4%to 14%(mass fraction).All LAZx32-0.5Y alloys contain AlLi and Al_(2)Y,while MgLi_(2)Al appears only in the alloy containing theβ-Li matrix.As the Li content increases,the content of AlLi and MgLi_(2)Al gradually increases,while the content of Al_(2)Y does not change much.As the Li content increases from 4%to 10%,the ultimate tensile strength and hardness of the as-cast LAZx32-0.5Y alloys gradually decrease while the elongation gradually increases.The corresponding fracture mechanism changes from cleavage fracture to quasi-cleavage fracture and then to microporous aggregation fracture.This is mainly attributed to the decrease ofα-Mg and the increase ofβ-Li in the alloy.When the Li content continues to increase to 10%and 14%,the yield strength,ultimate tensile strength and hardness of the as-cast LAZx32-0.5Y alloys gradually increase,while the elongation decreases sharply,which is mainly attributed to the nano-scale MgLi_(2)Al uniformly distributed in theβ-Li matrix.

Microstructure evolution and mechanical properties of rheo-processed ADC12 alloy

Microstructure evolution and mechanical properties of the rheo-processed ADC12 alloy were investigated by means ofoptical microscopy, X-ray diffraction and scanning electron microscopy. Primary dendritic Al of rheo-casting (RC) andrheo-diecasting (RDC) ADC12 alloys are sheared off. The average size, as well as solid fraction of the primary Al increase withdescending pouring temperature. The mechanical properties of alloys are strengthened by rheo-processing. Ultimate tensile strengthsof RC samples increase with the decrease of the pouring temperature, and reach the maximum in the range from 580 to 600 °C. Atpouring temperature of 595 °C, the RDC sample obtains the best ultimate tensile strength and elongation. Great reductions onporosity and primary Al globularization are crucial to the mechanical properties. Relationships of the primary Al size and yield stressare depicted with Hall?Petch equation.

Effects of rotating gas bubble stirring treatment on the microstructures of semi-solid AZ91-2Ca alloy

In this study,the effect of rotating gas bubble stirring treatment on the microstructures of semi-solid AZ91-2Ca alloy was investigated.The semi-solid slurry was produced by injecting fine gas bubbles into the melt through a rotating steel diffuser during solidification,and the samples of semi-solid slurry were taken by the rapid quenching method.The results show that fine and sphericalα-Mg particles can be obtained under rotating gas bubble stirring treatment.The process parameters such as gas flow rate,cooling rate and rotation speed have significant influence on the morphology of primary solid particles.After rotating gas bubble stirring treatment,the higher the particle density,the finer and rounder the primaryα-Mg particles.The formation of numerous solid particles is due to the combination mechanisms of copious nucleation and dendrite fragmentation.

Microstructural evolution and mechanical performance of cast Mg−3Nd−0.2Zn−0.5Zr alloy with Y additions

This work investigated the effects of different Y additions(0,1.5,3.0 and 4.5 wt.%)on the microstructural evolution and mechanical performance of cast Mg−3Nd−0.2Zn−0.5Zr alloy.The results show that as the Y content increases,the key secondary phases in as-cast alloys change from the Mg_(12)Nd type to the Mg_(24)Y_(5) type.Meanwhile,the number density of Zn−Zr particles in the grains of as-quenched alloys gradually decreases.HAADF-STEM observations of peak-aged samples reveal that element Y is greatly enriched in the globularβ¢precipitates,leading to a significantly increased volume fraction and promoted precipitation kinetics ofβ¢precipitates,resulting in enhanced strength of the alloy.Tensile tests reveal that,with the addition of 4.5 wt.%Y,the yield strength of the base alloy is substantially increased by 88 and 61 MPa after being aged at 200 and 225°C under peak-aged conditions,respectively.

Effect of heat treatments on microstructure and mechanical properties of sand cast Al−2Li−2Cu−0.5Mg−0.2Sc−0.2Zr alloy

This study focused on modifying heat treatment schemes to enhance the mechanical properties of sand cast Al−2Li−2Cu−0.5Mg−0.2Sc−0.2Zr alloy.Different three-stage solution treatment schemes((460℃,32 h)+(520℃,24 h)+(530/540/550℃,4/12/24/32 h))and aging temperatures(125,175,225℃)were designed for comparison.The microstructure evolutions were analyzed by optical microscopy(OM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results showed that the three-stage solution treatment of(460℃,32 h)+(520℃,24 h)+(530℃,12 h)could dissolve most of the secondary phases.The TEM results illustrated that fineδ'(Al_(3)Li)particles were homogeneously distributed in the matrix after aging at 175℃for 8 h,accompanied by a small amount of lath-shaped S′(Al_(2)CuMg)and plate-like T_(1)(Al_(2)CuLi)phases.The best comprehensive properties of yield strength of 376 MPa,ultimate tensile strength of 458 MPa and elongation of 4.1%were obtained by the optimal heat treatment scheme((460℃,32 h)+(520℃,24 h)+(530℃,12 h)+(175℃,8 h)).

Effect of Ca content and rheo-squeeze casting parameters on microstructure and mechanical properties of AZ91−1Ce−xCa alloys

The microstructure,mechanical properties and flame resistance behavior of the AZ91−1Ce alloys with different Ca additions were firstly investigated.Then,the effect of processing parameters,including applied pressures and rotation speeds,on the microstructure and mechanical properties of the rheo-squeeze casting AZ91−1Ce−2Ca alloy was studied.The results indicate that with the increase of Ca content,the microstructure is refined and the flame resistance of the AZ91−1Ce−xCa alloys increases.But when the Ca content exceeds 1 wt.%,with the Ca content increasing,the mechanical properties of the AZ91−1Ce−xCa alloys reduce rapidly.For rheo-squeeze casting process,the increase of applied pressure and rotation speed can both bring about significant refinement in the microstructure of the AZ91−1Ce−2Ca alloy and reduction of the porosity,so the mechanical properties increase.Compared to conventional casting,the AZ91−1Ce alloy with the addition of 2 wt.%Ca by rheo-squeeze casting not only guarantees the oxidation resistance(801℃),but also improves mechanical properties.

Effect of heat treatment on corrosion behavior of low pressure sand cast Mg-10Gd-3Y-0.5Zr alloys

The corrosion behaviors of low-pressure sand cast Mg-10Gd-3Y-0.5Zr(wt.%)alloys in as-cast,solution treated(T4)and aged(T6)conditions were studied by means of immersion test and electrochemical measurements in 5wt.%NaCl solution saturated with Mg(OH)_(2).It was observed that the corrosion rate in the T4 condition was lower than that of the as-cast and T6 conditions by both sand casting and permanent mold casting with the same order of as-cast>T6>T4;while the corrosion resistance of the permanent mold casting is superior to the sand casting.The morphologies of the corrosion products are similar porous structures consisting of tiny erect flakes perpendicular to the corroded surface of the alloy,irrespective of the heat treatment conditions.Especially,the corrosion film in T4 condition is more compact than that in the other two conditions.In addition,the severer corrosion happening to the as-cast condition is correlated with the galvanic corrosion between the matrix and the eutectic compounds;while improved corrosion resistance for the T4 and T6 conditions is ascribed to the dissolution of the secondary eutectic compounds.The measured corrosion current densities of Mg-10Gd-3Y-0.5Zr alloys in as-cast,T4,and T6 conditions are 36μA·cm^(-2),10μA·cm^(-2),and 33μA·cm^(-2),respectively.The proposed equivalent circuit[Rs(CPE_(1)R_(t)R_(f)CPE_(2))]by Zview software matches well with the tested electrochemical impedance spectra(EIS)data.

Effect of reclaimed sand additions on mechanical properties and fracture behavior of furan no-bake resin sand

In this work, the effects of reclaimed sand additions on the microstructure characteristics, mechanical properties and fracture behavior of furan no-bake resin sand have been investigated systematically within the temperature range from 25 to 600 oC. The addition of 20%-100% reclaimed sand showed dramatic strength deterioration effect at the same temperature, which is associated with the formation of bonding bridges. Both the ultimate tensile strength(UTS) and compressive strength(CS) of the moulding sand initially increase with the increase of temperature, and then sharply decrease with the further increase of temperature, which is attributed to the thermal decomposition of furan resin. The addition amount of reclaimed sand has a remarkable effect on the room temperature fracture mode, i.e., with the addition of 0-20% reclaimed sand, the fracture mode was mainly cohesive fracture; the fracture mode converts to be mixture fracture mode as the addition of reclaimed sand increases to 35%-70%; further increasing the addition to 100% results in the fracture mode of typical adhesive fracture. The fracture surface of the bonding bridge changes from a semblance of cotton or holes to smooth with the increase of test temperature.

Strengthening-toughening methods and mechanisms of Mg-Li alloy:a review

Magnesium-lithium(Mg-Li) alloy,as the lightest metal structure material,has unparalleled market prospects in aerospace,weapons and equipment,electronic technology,transportation,and many other fields.However,it is hard to balance the superlight and high strength of Mg-Li alloy,and the inferior high-temperature strength and poor high-temperature stability limit the wide application of Mg-Li alloy.At present,the main methods to improve the mechanical properties of Mg-Li alloy are alloying,grain refinement,and compound strengthening.The domestic and overseas research progress in the strengthening and toughening methods and mechanisms of Mg-Li alloy are reviewed,and the future development of the high strength and high toughness Mg-Li alloy is prospected.

Recent Progress in Fluorescent Formaldehyde Detection Using Small Molecule Probes

Formaldehyde(FA,a typical reactive carbonyl species)is a well-known environmental pollutant and a disease-related biomarker,making its sensitive and selective detection significant.Fluorescent probes have been explored for FA perception in environment,intracellular media and in vivo.In this review,we majorly conclude the recently represented fluorescence FA analysis based on small molecule probes.The general FA sensing mechanisms are first introduced.Regarding the FA detection in various environments,sensing tactics and performances are discussed in order of natural environment,living cells and in vivo.In the end,this review discusses the challenges and future trends of FA detection based on fluorescent probes.