The impact of rolling temperature and the crystallographic orientation ofα-colonies on the globularization behavior of lamellarα+βmicrostructure in Ti-6Al-4V alloy was investigated.Firstly,the lamellar structure wa...The impact of rolling temperature and the crystallographic orientation ofα-colonies on the globularization behavior of lamellarα+βmicrostructure in Ti-6Al-4V alloy was investigated.Firstly,the lamellar structure was heavily rolled at 600,700,800 and 900°C,respectively.Heavy rolling from temperatures of 600 to 900°C resulted in an increased volume fraction and thickness ofβlamellae,while the corresponding parameters forαlamellae decreased.Then,these rolledα+βlamellar microstructures were spheroidized into equiaxed grains upon subsequent annealing.The results demonstrate that the globularization fraction of the lamellar structures diminishes as the rolling temperature increases.Additionally,the globularization fraction forα-colonies with hard crystallographic orientations,such as<0001>//ND and<0001>//TD,is considerably lower compared to those with softer orientations,positioned at certain angles to ND,RD,and TD during annealing process.This results in heterogeneous globularization ofαlamellae,leading to the development of pronounced sharp micro-texture.Furthermore,the slipping deformations ofα-colonies with varying crystallographic orientations during rolling were meticulously analyzed.展开更多
A lamellar-structure TC21 titanium alloy was hot-rolled and subsequently annealed at 820,880 and 940℃ for 1 and 6 h,and the effects of annealing parameters on static globularization and morphology evolution of bothα...A lamellar-structure TC21 titanium alloy was hot-rolled and subsequently annealed at 820,880 and 940℃ for 1 and 6 h,and the effects of annealing parameters on static globularization and morphology evolution of bothαandβphases were studied.The results show thatαglobularization process is sluggish due to the limited boundary splitting at 820℃.With increasing temperature to 880℃,the accelerated boundary splitting and termination migration promote theαglobularization.At 820 and 880℃,the static recovery(SRV)and recrystallization(SRX)induce the grain refinement of interlamellarβphase.However,the excessively high temperature of 940℃ results in the coarsening ofαgrains due to the assistance of Ostwald ripening,and produces coarseβgrains mainly due to the absence of SRX in interlamellarβphases.Conclusively,880℃ is an appropriate annealing temperature to produce a homogeneous microstructure in which globularizedαand refinedβgrains distribute homogeneously.展开更多
The dynamic globularization kinetics of TA15（Ti-6Al-2Zr-1Mo-1V） titanium alloy with a colony α microstructure during deformation at temperature range of 860-940 ℃ and strain rate range of 0.01-10 s-1 was quantitat...The dynamic globularization kinetics of TA15（Ti-6Al-2Zr-1Mo-1V） titanium alloy with a colony α microstructure during deformation at temperature range of 860-940 ℃ and strain rate range of 0.01-10 s-1 was quantitatively studied through isothermal compression tests.It is found that the dynamic globularization kinetics and the kinetics rate of TA15 are sensitive to deformation parameters.The dynamic globularized fraction increases with increasing strain,temperature but decreasing strain rate.The variation of globularized fraction with strain approximately follows an Avrami type equation.Using the Avrami type equation,the initiation and completion strains for dynamic globularization of TA15 were predicted to be 0.34-0.59 and 3.40-6.80.The kinetics rate of dynamic globularization increases with strain at first,then decreases.The peak value of kinetics rate,which corresponds to 20%-33% globularization fraction,increases with increasing temperature and decreasing strain rate.展开更多
Hot deformation behavior and globularization mechanism of Ti6A14V0.1B alloy with lamellar micro structure were quantitatively studied through isothermal compression tests with the temperature range of 850950 ℃and str...Hot deformation behavior and globularization mechanism of Ti6A14V0.1B alloy with lamellar micro structure were quantitatively studied through isothermal compression tests with the temperature range of 850950 ℃and strain rate range of 0.011.00 s1. The results show that the peak flow stress and steady stress are sensitive to the strain rate and temperature. The value of deformation activation energy is 890.49 kJmo11 in （a＋β） region. Dynamic recrystallization is the major deformation mecha nism. Flow softening is dominated by dynamic recrystallization at 850950 ℃. TiB particles promote the recrystallization of laths. Globularization processes consist of four steps： for mation of subgrain after dynamic recovery in a plates; subgrain boundary migration caused by interracial instability; interfacial migration promoting phase wedge into a phase; disintegrating of a laths by diffusion processes; and grain boundary sliding. Globularization mechanisms during hot deformation processes of the Ti6A14V0.1B alloy with lamellar structure are continuous dynamic recrystallization.展开更多
The hot deformation behavior,microstructure evolution and fracture characteristics of bimodal microstructured Ti-6Al-2Zr-1Mo-1V alloy were investigated by isothermal tensile tests.Results reveal that flow softening is...The hot deformation behavior,microstructure evolution and fracture characteristics of bimodal microstructured Ti-6Al-2Zr-1Mo-1V alloy were investigated by isothermal tensile tests.Results reveal that flow softening is caused by dynamic globularization of the bimodal microstructure,which also results in a relatively high stress exponent and thermal activation energy.The corresponding SEM,EBSD and TEM observations indicate that the dynamic globularization at750and800℃is accomplished by the formation ofα/αsub-grain boundary and penetration of theβphase.However,dynamic recrystallization(DRX)is the main globularization mechanism at850℃,which was proved by the generation of fine grains with a necklace-like character due to the transformation of low-angle boundaries(LABs)into high-angle boundaries(HABs).With an increase in the deformation temperature or a decrease in the strain rate,the fracture mechanism changes from microvoid coalescence to intergranular fracture.展开更多
The flow behavior and dynamic globularization of TC11 titanium alloy during subtransus deformation are investigated through hot compression tests. A constitutive model is established based on physical-based hardening ...The flow behavior and dynamic globularization of TC11 titanium alloy during subtransus deformation are investigated through hot compression tests. A constitutive model is established based on physical-based hardening model and phenomenological softening model. And based on the recrystallization mechanisms of globularization, the Avrami type kinetics model is established for prediction of globularization fraction and globularized grain size under large strain subtransus deformation of TC11 alloy. As the preliminary application of the previous results, the cogging process of large size TC11 alloy billet is simulated. Based on subroutine development of the DEFORM software, the coupled simulation of one fire cogging process is developed. It shows that the predicted results are in good agreement with the experimental results in forging load and microstructure characteristic, which validates the reliability of the developed FEM subroutine models.展开更多
The globularization behavior and mechanism of TC17 alloy with basketweave microstructure were investigated, and the models of dynamic and static globularization kinetics were established. The quantitative and metallog...The globularization behavior and mechanism of TC17 alloy with basketweave microstructure were investigated, and the models of dynamic and static globularization kinetics were established. The quantitative and metallographic results show that the globularization of α phase is sensitive to the parameters of deformation and heat treatment. By EBSD analysis, the formation and evolution mechanisms of intra-α boundaries are related to discontinuous dynamic recrystallization and continuous dynamic recrystallization, which can form α grains with high and low misorientations between neighbour grains after the heat treatment, respectively. Based on the globularization behavior and mechanism, two modified JMAK models are developed to predict the dynamic and static globularization kinetics, and the mean absolute relative errors(MARE) of 10.67% and 13.80% indicate the accuracy of the dynamic and static globularization kinetics models. The results of this work can provide guidance for controlling microstructure of titanium alloy.展开更多
Microstructure with globularαphase is desirable as it contributes to preferable comprehensive mechanical properties for titanium alloys.However,titanium alloys fabricated by directed energy deposition(DED)are mainly ...Microstructure with globularαphase is desirable as it contributes to preferable comprehensive mechanical properties for titanium alloys.However,titanium alloys fabricated by directed energy deposition(DED)are mainly characterized by the lamellarαphase within the basket-weave microstructure,which often leads to severe anisotropy and inferior low cycle fatigue(LCF)properties.To address this,the subcritical annealing and the cyclic annealing were applied to DED Ti–6Al–4V in order to achieve the transformation from the lamellarαphase to the globularαphase.The microstructural characteristics and the globularization behavior ofαphase during heat treatment were investigated.The results show that the aspect ratio ofαis significantly decreased with the subcritical annealing due to the coarsening of lamellarα.Furthermore,the globularαis obtained with the cyclic annealing as a combination result of the termination dissolution and the side surface growth of the lamellarα.These contribute to a pronounced reduction of 85.4%in the ductility anisotropy,compared with the as-built specimens,and superior comprehensive mechanical properties including LCF are achieved with the formation of globularα.展开更多
Lamellar globularization in the dual-phase titanium alloy is the key to improving plasticity and strength.However,the mechanism has not been fully elucidated so far.In this work,the role of phase/grain bound-ary in th...Lamellar globularization in the dual-phase titanium alloy is the key to improving plasticity and strength.However,the mechanism has not been fully elucidated so far.In this work,the role of phase/grain bound-ary in the static globularization of TC17 alloy was systematically studied by setting differentαphase con-tent before annealing through low-and high-temperature deformation.Isothermal compression causes the parallel distribution and fragmentation of 3Dαplates and few globularαparticles are formed at a strain rate of 1 s^(-1).Post-deformation annealing promotes the static globularization ofαphase while it is affected by initialαphase content.After 730°C deformation,the development ofα/αinterface by absorbing dislocations promotes the formation of globularαgrains based on the nucleation of sepa-ratedαparticles and pre-recoveryαsubgrain during subsequent annealing.Theα/α/βandα/β/βtriple junctions formed due to highαcontent with about 36%volume fraction are favorable for the further nucleation and growth of globularαgrains by reducing interface energy,forming a 3D irregularαplate.Then nucleation and growth of theβphase dominate the microstructure evolution during subsequent an-nealing,resulting in the local dissolution of the plate and formation ofαrods.After 850°C deformation,theαphase tends to nucleate at theβ/β/βtriple junctions and grow into a lamellar shape along the high energyβ/βgrain boundary due to lowαcontent with about 7%volume fraction.Theαnucleation that maintains the Burgers orientation relationship(BOR)with the surroundingβphase grows along the habit plane and thickens slowly,resulting in the formation of a precipitatedαplate with a flat surface and the suppression of static globularization.The comprehensive investigation of lamellar globularization provides guidance for optimizing the 3D microstructure and properties of dual-phase titanium alloy.展开更多
The microstructure evolution during annealing of Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy was investigated. The results show that for the alloy compressed at 810 °C and 1.0 s^-1, deformation amount（height reduction） 20% an...The microstructure evolution during annealing of Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy was investigated. The results show that for the alloy compressed at 810 °C and 1.0 s^-1, deformation amount（height reduction） 20% and 50% and annealed at 810 °C, thermal grooving by penetration of β phase is sufficient during the first 20 min annealing, resulting in a sharp increase in globularization fraction. The globularization fraction continuously increases with the increase of annealing time, and a height reduction of 50% leads to a near globular microstructure after annealing for 4 h. For the alloy with deformation amount of 50% by compressing at 810 °C, 0.01 s^-1, and then annealed at 810 °C, thermal grooving is limited during the first 20 min of annealing and large quantities of high-angle grain boundaries（HABs） remain. With long time annealing, the chain-like α grains are developed due to the HABs, termination migration and Ostwald ripening. The present results suggest that a higher strain rate and a larger height reduction are necessary before annealing to achieve a globular microstructure of Ti-5Al-2Sn-2Zr-4Mo-4Cr.展开更多
We present a polarization study of 25 globular cluster(GC)pulsars observed with the Five-hundred-meter Aperture Spherical radio Telescope(FAST),including 15 pro les measured for the rst time.The pulse width–period re...We present a polarization study of 25 globular cluster(GC)pulsars observed with the Five-hundred-meter Aperture Spherical radio Telescope(FAST),including 15 pro les measured for the rst time.The pulse width–period relationships for millisecond pulsars(MSPs)in GCs follow power-law indices of-0.268(W10)and-0.330(W50),consistent with normal pulsars.Only 20%of the sample exhibit clear S-shaped position angle curves-signi cantly fewer than in the normal pulsar population.Rotation Measures(RMs)for these pulsars suggest that GCs near the Galactic plane show higher RMs,in agreement with former studies.Polarization ratios were measured,with M53A showing the highest linear polarization(56%)and M15H the highest absolute circular polarization(37%).On average,GC pulsars exhibit lower circular(-1%)and absolute circular(11%)polarization compared to normal pulsars observed with Parkes(5%and 32%,respectively).However,their polarization distributions align with MSPs in the Galactic plane,suggesting GC environments do not drastically alter emission properties.展开更多
The growing interest in skeletal muscle regeneration is associated with the opening of new therapeutic strategies for muscle injury after trauma, as well as several muscular degenerative pathologies, including dystrop...The growing interest in skeletal muscle regeneration is associated with the opening of new therapeutic strategies for muscle injury after trauma, as well as several muscular degenerative pathologies, including dystrophies, muscu- lar atrophy, and cachexia. Studies focused on the ability of extracellular factors to promote myogenesis are therefore highly promising. We now report that an adipocyte-derived factor, globular adiponectin （gAd）, is able to induce mus- cle gene expression and cell differentiation, gAd, besides its well-known ability to regulate several metabolic func- tions in muscle, including glucose uptake and consumption and fatty acid catabolism, is able to block cell cycle entry of myoblasts, to induce the expression of specific skeletal muscle markers such as myosin heavy chain or caveolin-3, as well as to provoke cell fusion into multinucleated syncytia and, finally, muscle fibre formation, gAd exerts its pro- differentiative activity through redox-dependent activation of p38, Akt and 5＇-AMP-activated protein kinase path- ways. Interestingly, differentiating myoblasts are autocrine for adiponectin, and the mimicking of pro-inflammatory settings or exposure to oxidative stress strongly increases the production of the hormone from differentiating cells. These data suggest a novel function of adiponectin, directly coordinating the myogenic differentiation program and serving an autocrine function during skeletal myogenesis.展开更多
Binary stars are common in star clusters and galaxies, but the detailed ef- fects of binary evolution are not taken into account in some color-magnitude diagram （CMD） studies. This paper studies the CMDs of twelve g...Binary stars are common in star clusters and galaxies, but the detailed ef- fects of binary evolution are not taken into account in some color-magnitude diagram （CMD） studies. This paper studies the CMDs of twelve globular clusters via binary- star stellar populations. The observational CMDs of the star clusters are compared to those of binary-star populations, and then the stellar metallicities, ages, distances and reddenings of these star clusters are obtained. The paper also tests the different effects of binary and single stars on CMD studies. It is shown that binaries can better fit the observational CMDs of the sample globular clusters compared to single stars. This suggests that the effects of binary evolution should be considered when modeling the CMDs and stellar populations of star clusters and galaxies.展开更多
Semi solid metallurgy offers distinct advantages over other near-net-shape manufacturing processes. By this process, components are produced from slurry kept at a temperature between the solidus and the liquidus isoth...Semi solid metallurgy offers distinct advantages over other near-net-shape manufacturing processes. By this process, components are produced from slurry kept at a temperature between the solidus and the liquidus isotherms, resulting in breakdown of the dendritic structure. A new structure in which the morphology of the crystals of the primary phase is globular evolves. In this present paper, the importance of globular structure is identified. The theories of evolution of globular crystals in thixo–processing are identified and discussed.展开更多
The sensitivity analysis functions on globularized fraction ofαlamellae were established using a physically-based microstructure model and gradient method.These functions were applied to the sensitivity analysis on g...The sensitivity analysis functions on globularized fraction ofαlamellae were established using a physically-based microstructure model and gradient method.These functions were applied to the sensitivity analysis on globularized fraction ofαlamellae in TC17 alloy.The material constants in these functions are determined using the genetic algorithm-based objective optimization technique.The globularized fraction ofαlamellae during isothermal compression of TC17 alloy was quantitatively analyzed based on scanning electron microscopy(SEM)observation.The results show thatαlamellae mostly change to equiaxedαgrains at a deformation temperature of 1083 K,a strain rate of 0.01 s^-1 and a strain of 1.2.The globularized fraction decreases with increasing strain rate because lower strain rate provides enough time for the spheroidization.The effect of deformation temperature on the globularized fraction is controlled by the strain rate.And,the predicted derivations of globularized fraction with respect to processing parameters show good agreement with the experimental values.展开更多
In this paper,~12 yr long-term Pass 8 data from Fermi Large Area Telescope for the 157 globular clusters are carefully re-analyzed.Besides the 31 globular clusters reported in the fourth Fermi Large Area Telescope cat...In this paper,~12 yr long-term Pass 8 data from Fermi Large Area Telescope for the 157 globular clusters are carefully re-analyzed.Besides the 31 globular clusters reported in the fourth Fermi Large Area Telescope catalog Data Release 2,NGC 1851 is identified as a gamma-ray emitter and the significant gamma-ray emissions from NGC 6715 and NGC 6723 are detected.Especially NGC 6715 is located at a distance of 26.8 kpc,so far it is the farthest globular cluster detected in gamma-rays.A detailed analysis for these three globular clusters has been performed,but their gamma-ray pulsation emissions or flux variabilities are not found.The numbers of millisecond pulsars(MSPs)in these globular clusters are estimated under the assumption that each MSP inside globular clusters emits a similar amount of gamma-rays.Some possible origins of gamma-ray emission from globular clusters,such as MSPs,pulsar binary systems and/or dark matter,are discussed.展开更多
The character of forming long-range contacts affects the three-dimensional structure of globular proteins deeply. As the different ability to form long-range contacts between 20 types of amino acids and 4 categories o...The character of forming long-range contacts affects the three-dimensional structure of globular proteins deeply. As the different ability to form long-range contacts between 20 types of amino acids and 4 categories of globular proteins, the statistical properties are thoroughly discussed in this paper. Two parameters NC and ND are defined to confine the valid residues in detail. The relationship between hydrophobieity scales and valid residue percentage of each amino acid is given in the present work and the linear functions are shown in our statistical results. It is concluded that the hydrophobicity scale defined by chemical derivatives of the amino acids and nonpolar phase of large unilamellar vesicle membranes is the most effective technique to characterise the hydrophobic behavior of amino acid residues. Meanwhile, residue percentage Pi and sequential residue length Li of a certain protein i are calculated under different conditions. The statistical results show that the average value of Pi as well as Li of all-α proteins has a minimum among these 4 classes of globular proteins, indicating that all-α proteins are hardly capable of forming long-range contacts one by one along their linear amino acid sequences. All-β proteins have a higher tendency to construct long-range contacts along their primary sequences related to the secondary configurations, i.e. parallel and anti-parallel configurations of/3 sheets. The investigation of the interior properties of globular proteins give us the connection between the three-dimensional structure and its primary sequence data or secondary configurations, and help us to understand the structure of protein and its folding process well.展开更多
We aim to retrieve ghost streams under the assumption that all the globular clusters in our Galaxy were formed in very early merge events. Our results are based on two speculations： that the specific energy and angul...We aim to retrieve ghost streams under the assumption that all the globular clusters in our Galaxy were formed in very early merge events. Our results are based on two speculations： that the specific energy and angular momentum of the globular clusters after merge are not changed in the course of evolution and that the globular clusters with a common origin would stay in the same orbit plane as the parent galaxy. After taking into account the apogalacticum distance of the orbits, we suggest with some Confidence five possible streams. The number of streams is consistent with the previous results. Three of the four well established members of the Sagittadus stream were found to be in one of our streams. Several other globular clusters in our result were also thought to come from accretion by previous researchers. The orbital parameters of the streams are derived, which provide a way to test whether these streams are true with the help of more accurate measurement of proper motions of the globular clusters.展开更多
The analysis of residue-residue contacts in protein structures can shed some light on our understanding of the folding and stability of proteins. In this paper, we study the statistical properties of long-range and sh...The analysis of residue-residue contacts in protein structures can shed some light on our understanding of the folding and stability of proteins. In this paper, we study the statistical properties of long-range and short-range residue- residue contacts of 91 globular proteins using CSU software and analyze the importance of long-range contacts in globular protein structure. There are many short-range and long-range contacts in globular proteins, and it is found that the average number of long-range contacts per residue is 5.63 and the percentage of residue-residue contacts which are involved in long- range ones is 59.4%. In more detail, the distribution of long-range contacts in different residue intervals is investigated and it is found that the residues occurring in the interval range of 4-10 residues apart in the sequence contribute more long-range contacts to the stability of globular protein. The number of long-range contacts per residue, which is a measure of ability to form residue-residue contacts, is also calculated for 20 different amino acid residues. It is shown that hydrophobic residues (including Leu, Val, He, Met, Phe, Tyr, Cys and Trp) having a large number of long-range contacts easily form long-range contacts, while the hydrophilic amino acids (including Ala, Gly, Thr, His, Glu, Gln, Asp, Asn, Lys, Ser, Arg, and Pro) form long-range contacts with more difficulty. The relationship between the Fauchere-Pliska hydrophobicity scale (FPH) and the number of short-range and long-range contacts per residue for 20 amino acid residues is also studied. An approximately linear relationship between the Fauchere-Pliska hydrophobicity scale (FPH) and the number of long-range contacts per residue CL, is found and can be expressed as CL = a + b × FPH where a = 5.04 and b = 1.23. These results can help us to understand the role of residue-residue contacts in globular protein structure.展开更多
The sixth Data Release （DR6） of the Sloan Digital Sky Survey （SDSS） provides more photometric regions, new features and more accurate data around globular cluster Palomar 5. A new method, Back Propagation Neural N...The sixth Data Release （DR6） of the Sloan Digital Sky Survey （SDSS） provides more photometric regions, new features and more accurate data around globular cluster Palomar 5. A new method, Back Propagation Neural Network （BPNN）, is used to estimate the cluster membership probability in order to detect its tidal tails. Cluster and field stars, used for training the networks, are extracted over a 40 × 20 deg^2 field by color-magnitude diagrams （CMDs）. The best BPNNs with two hidden layers and a Levenberg-Marquardt （LM） training algorithm are determined by the chosen cluster and field samples. The membership probabilities of stars in the whole field are obtained with the BPNNs, and contour maps of the probability distribution show that a tail extends .5.42° to the north of the cluster and another tail extends 3.77° to the south. The tails are similar to those detected by Odenkirchen et al., but no more debris from the cluster is found to the northeast in the sky. The radial density profiles are investigated both along the tails and near the cluster center. Quite a few substructures are discovered in the tails. The number density profile of the cluster is fitted with the King model and the tidal radius is determined as 14.28＇. However, the King model cannot fit the observed profile at the outer regions （R 〉 8＇） because of the tidal tails generated by the tidal force. Luminosity functions of the cluster and the tidal tails are calculated, which confirm that the tails originate from Palomar 5.展开更多
文摘The impact of rolling temperature and the crystallographic orientation ofα-colonies on the globularization behavior of lamellarα+βmicrostructure in Ti-6Al-4V alloy was investigated.Firstly,the lamellar structure was heavily rolled at 600,700,800 and 900°C,respectively.Heavy rolling from temperatures of 600 to 900°C resulted in an increased volume fraction and thickness ofβlamellae,while the corresponding parameters forαlamellae decreased.Then,these rolledα+βlamellar microstructures were spheroidized into equiaxed grains upon subsequent annealing.The results demonstrate that the globularization fraction of the lamellar structures diminishes as the rolling temperature increases.Additionally,the globularization fraction forα-colonies with hard crystallographic orientations,such as<0001>//ND and<0001>//TD,is considerably lower compared to those with softer orientations,positioned at certain angles to ND,RD,and TD during annealing process.This results in heterogeneous globularization ofαlamellae,leading to the development of pronounced sharp micro-texture.Furthermore,the slipping deformations ofα-colonies with varying crystallographic orientations during rolling were meticulously analyzed.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(No.51971046)the Fundamental Research Funds for the Central Universities,China(No.2020CDJGFCL005)。
文摘A lamellar-structure TC21 titanium alloy was hot-rolled and subsequently annealed at 820,880 and 940℃ for 1 and 6 h,and the effects of annealing parameters on static globularization and morphology evolution of bothαandβphases were studied.The results show thatαglobularization process is sluggish due to the limited boundary splitting at 820℃.With increasing temperature to 880℃,the accelerated boundary splitting and termination migration promote theαglobularization.At 820 and 880℃,the static recovery(SRV)and recrystallization(SRX)induce the grain refinement of interlamellarβphase.However,the excessively high temperature of 940℃ results in the coarsening ofαgrains due to the assistance of Ostwald ripening,and produces coarseβgrains mainly due to the absence of SRX in interlamellarβphases.Conclusively,880℃ is an appropriate annealing temperature to produce a homogeneous microstructure in which globularizedαand refinedβgrains distribute homogeneously.
基金Project(50935007)supported by the National Natural Science Foundation of ChinaProject(2010CB731701)supported by the National Basic Research Program of China
文摘The dynamic globularization kinetics of TA15（Ti-6Al-2Zr-1Mo-1V） titanium alloy with a colony α microstructure during deformation at temperature range of 860-940 ℃ and strain rate range of 0.01-10 s-1 was quantitatively studied through isothermal compression tests.It is found that the dynamic globularization kinetics and the kinetics rate of TA15 are sensitive to deformation parameters.The dynamic globularized fraction increases with increasing strain,temperature but decreasing strain rate.The variation of globularized fraction with strain approximately follows an Avrami type equation.Using the Avrami type equation,the initiation and completion strains for dynamic globularization of TA15 were predicted to be 0.34-0.59 and 3.40-6.80.The kinetics rate of dynamic globularization increases with strain at first,then decreases.The peak value of kinetics rate,which corresponds to 20%-33% globularization fraction,increases with increasing temperature and decreasing strain rate.
基金supported by the International Science and Technology Corporation Foundation of China(No.2012DFG51540)
文摘Hot deformation behavior and globularization mechanism of Ti6A14V0.1B alloy with lamellar micro structure were quantitatively studied through isothermal compression tests with the temperature range of 850950 ℃and strain rate range of 0.011.00 s1. The results show that the peak flow stress and steady stress are sensitive to the strain rate and temperature. The value of deformation activation energy is 890.49 kJmo11 in （a＋β） region. Dynamic recrystallization is the major deformation mecha nism. Flow softening is dominated by dynamic recrystallization at 850950 ℃. TiB particles promote the recrystallization of laths. Globularization processes consist of four steps： for mation of subgrain after dynamic recovery in a plates; subgrain boundary migration caused by interracial instability; interfacial migration promoting phase wedge into a phase; disintegrating of a laths by diffusion processes; and grain boundary sliding. Globularization mechanisms during hot deformation processes of the Ti6A14V0.1B alloy with lamellar structure are continuous dynamic recrystallization.
基金Project (LQ18E050007) supported by the Natural Science Foundation of Zhejiang Province,ChinaProject (20120006110017) supported by the Research Fund for the Doctoral Program of Higher Education,China
文摘The hot deformation behavior,microstructure evolution and fracture characteristics of bimodal microstructured Ti-6Al-2Zr-1Mo-1V alloy were investigated by isothermal tensile tests.Results reveal that flow softening is caused by dynamic globularization of the bimodal microstructure,which also results in a relatively high stress exponent and thermal activation energy.The corresponding SEM,EBSD and TEM observations indicate that the dynamic globularization at750and800℃is accomplished by the formation ofα/αsub-grain boundary and penetration of theβphase.However,dynamic recrystallization(DRX)is the main globularization mechanism at850℃,which was proved by the generation of fine grains with a necklace-like character due to the transformation of low-angle boundaries(LABs)into high-angle boundaries(HABs).With an increase in the deformation temperature or a decrease in the strain rate,the fracture mechanism changes from microvoid coalescence to intergranular fracture.
文摘The flow behavior and dynamic globularization of TC11 titanium alloy during subtransus deformation are investigated through hot compression tests. A constitutive model is established based on physical-based hardening model and phenomenological softening model. And based on the recrystallization mechanisms of globularization, the Avrami type kinetics model is established for prediction of globularization fraction and globularized grain size under large strain subtransus deformation of TC11 alloy. As the preliminary application of the previous results, the cogging process of large size TC11 alloy billet is simulated. Based on subroutine development of the DEFORM software, the coupled simulation of one fire cogging process is developed. It shows that the predicted results are in good agreement with the experimental results in forging load and microstructure characteristic, which validates the reliability of the developed FEM subroutine models.
基金the support from the Science Fund for Distinguished Young Scholars from Shaanxi Province, China (No. 2020JC-17)the National Natural Science Foundation of China (No. 51705425)+1 种基金the Research Fund of the State Key Laboratory of Solidification Processing (NWPU), China (No. 2019-QZ-04)the Fundamental Research Funds for the Central Universities, China (No. 3102019PY007)。
文摘The globularization behavior and mechanism of TC17 alloy with basketweave microstructure were investigated, and the models of dynamic and static globularization kinetics were established. The quantitative and metallographic results show that the globularization of α phase is sensitive to the parameters of deformation and heat treatment. By EBSD analysis, the formation and evolution mechanisms of intra-α boundaries are related to discontinuous dynamic recrystallization and continuous dynamic recrystallization, which can form α grains with high and low misorientations between neighbour grains after the heat treatment, respectively. Based on the globularization behavior and mechanism, two modified JMAK models are developed to predict the dynamic and static globularization kinetics, and the mean absolute relative errors(MARE) of 10.67% and 13.80% indicate the accuracy of the dynamic and static globularization kinetics models. The results of this work can provide guidance for controlling microstructure of titanium alloy.
基金This work was financially supported by the National Natural Science Foundation of China(No.52275381)the Nation Defense Basic Scientific Research Program of China(No.JCKY2017204A021)the Shaanxi Province double chain fusion project(No.2021LLRH-08).
文摘Microstructure with globularαphase is desirable as it contributes to preferable comprehensive mechanical properties for titanium alloys.However,titanium alloys fabricated by directed energy deposition(DED)are mainly characterized by the lamellarαphase within the basket-weave microstructure,which often leads to severe anisotropy and inferior low cycle fatigue(LCF)properties.To address this,the subcritical annealing and the cyclic annealing were applied to DED Ti–6Al–4V in order to achieve the transformation from the lamellarαphase to the globularαphase.The microstructural characteristics and the globularization behavior ofαphase during heat treatment were investigated.The results show that the aspect ratio ofαis significantly decreased with the subcritical annealing due to the coarsening of lamellarα.Furthermore,the globularαis obtained with the cyclic annealing as a combination result of the termination dissolution and the side surface growth of the lamellarα.These contribute to a pronounced reduction of 85.4%in the ductility anisotropy,compared with the as-built specimens,and superior comprehensive mechanical properties including LCF are achieved with the formation of globularα.
基金the financial support from the National Key R&D Program of China(Grant No.2022YFB3707201)the Science Fund for Distinguished Young Scholars from Shaanxi Province(No.2020JC-17)+2 种基金NPU AoXiang Distinguished Young Schol-ars(Grant Nos.0604022GH0202143,0604022SH0201143)the Funding of Young Top-notch Talent of the National Ten Thousand Talent Program,the Fundamental Research Funds for the Central Universities(No.3102022gxb004)Science Center for Gas Tur-bine Project(No.P2022-A-IV-001-002)。
文摘Lamellar globularization in the dual-phase titanium alloy is the key to improving plasticity and strength.However,the mechanism has not been fully elucidated so far.In this work,the role of phase/grain bound-ary in the static globularization of TC17 alloy was systematically studied by setting differentαphase con-tent before annealing through low-and high-temperature deformation.Isothermal compression causes the parallel distribution and fragmentation of 3Dαplates and few globularαparticles are formed at a strain rate of 1 s^(-1).Post-deformation annealing promotes the static globularization ofαphase while it is affected by initialαphase content.After 730°C deformation,the development ofα/αinterface by absorbing dislocations promotes the formation of globularαgrains based on the nucleation of sepa-ratedαparticles and pre-recoveryαsubgrain during subsequent annealing.Theα/α/βandα/β/βtriple junctions formed due to highαcontent with about 36%volume fraction are favorable for the further nucleation and growth of globularαgrains by reducing interface energy,forming a 3D irregularαplate.Then nucleation and growth of theβphase dominate the microstructure evolution during subsequent an-nealing,resulting in the local dissolution of the plate and formation ofαrods.After 850°C deformation,theαphase tends to nucleate at theβ/β/βtriple junctions and grow into a lamellar shape along the high energyβ/βgrain boundary due to lowαcontent with about 7%volume fraction.Theαnucleation that maintains the Burgers orientation relationship(BOR)with the surroundingβphase grows along the habit plane and thickens slowly,resulting in the formation of a precipitatedαplate with a flat surface and the suppression of static globularization.The comprehensive investigation of lamellar globularization provides guidance for optimizing the 3D microstructure and properties of dual-phase titanium alloy.
基金Project(51275416)supported by the National Natural Science Foundation of ChinaProject(KP201513)supported by the Fund of the State Key Laboratory of Solidification Processing in NWPU,China
文摘The microstructure evolution during annealing of Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy was investigated. The results show that for the alloy compressed at 810 °C and 1.0 s^-1, deformation amount（height reduction） 20% and 50% and annealed at 810 °C, thermal grooving by penetration of β phase is sufficient during the first 20 min annealing, resulting in a sharp increase in globularization fraction. The globularization fraction continuously increases with the increase of annealing time, and a height reduction of 50% leads to a near globular microstructure after annealing for 4 h. For the alloy with deformation amount of 50% by compressing at 810 °C, 0.01 s^-1, and then annealed at 810 °C, thermal grooving is limited during the first 20 min of annealing and large quantities of high-angle grain boundaries（HABs） remain. With long time annealing, the chain-like α grains are developed due to the HABs, termination migration and Ostwald ripening. The present results suggest that a higher strain rate and a larger height reduction are necessary before annealing to achieve a globular microstructure of Ti-5Al-2Sn-2Zr-4Mo-4Cr.
基金supported by the National Key R&D Program of China,No.2022YFC2205202the National Natural Science Foundation of China(NSFC)under grant Nos.12173052,U2031119,11773041 and 11703047+2 种基金supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences(CAS)(id.Y2022027)the CAS“Light of West China”Programthe CAS President’s International Fellowship Initiative(grant No.2021FSM0004).
文摘We present a polarization study of 25 globular cluster(GC)pulsars observed with the Five-hundred-meter Aperture Spherical radio Telescope(FAST),including 15 pro les measured for the rst time.The pulse width–period relationships for millisecond pulsars(MSPs)in GCs follow power-law indices of-0.268(W10)and-0.330(W50),consistent with normal pulsars.Only 20%of the sample exhibit clear S-shaped position angle curves-signi cantly fewer than in the normal pulsar population.Rotation Measures(RMs)for these pulsars suggest that GCs near the Galactic plane show higher RMs,in agreement with former studies.Polarization ratios were measured,with M53A showing the highest linear polarization(56%)and M15H the highest absolute circular polarization(37%).On average,GC pulsars exhibit lower circular(-1%)and absolute circular(11%)polarization compared to normal pulsars observed with Parkes(5%and 32%,respectively).However,their polarization distributions align with MSPs in the Galactic plane,suggesting GC environments do not drastically alter emission properties.
文摘The growing interest in skeletal muscle regeneration is associated with the opening of new therapeutic strategies for muscle injury after trauma, as well as several muscular degenerative pathologies, including dystrophies, muscu- lar atrophy, and cachexia. Studies focused on the ability of extracellular factors to promote myogenesis are therefore highly promising. We now report that an adipocyte-derived factor, globular adiponectin （gAd）, is able to induce mus- cle gene expression and cell differentiation, gAd, besides its well-known ability to regulate several metabolic func- tions in muscle, including glucose uptake and consumption and fatty acid catabolism, is able to block cell cycle entry of myoblasts, to induce the expression of specific skeletal muscle markers such as myosin heavy chain or caveolin-3, as well as to provoke cell fusion into multinucleated syncytia and, finally, muscle fibre formation, gAd exerts its pro- differentiative activity through redox-dependent activation of p38, Akt and 5＇-AMP-activated protein kinase path- ways. Interestingly, differentiating myoblasts are autocrine for adiponectin, and the mimicking of pro-inflammatory settings or exposure to oxidative stress strongly increases the production of the hormone from differentiating cells. These data suggest a novel function of adiponectin, directly coordinating the myogenic differentiation program and serving an autocrine function during skeletal myogenesis.
基金supported by the National Natural Science Foundation of China (Grant No. 10963001)Yunnan Science Foundation(2009CD093)the Scientific Research Foundation of Dali University (DYKF2009 No. 1)
文摘Binary stars are common in star clusters and galaxies, but the detailed ef- fects of binary evolution are not taken into account in some color-magnitude diagram （CMD） studies. This paper studies the CMDs of twelve globular clusters via binary- star stellar populations. The observational CMDs of the star clusters are compared to those of binary-star populations, and then the stellar metallicities, ages, distances and reddenings of these star clusters are obtained. The paper also tests the different effects of binary and single stars on CMD studies. It is shown that binaries can better fit the observational CMDs of the sample globular clusters compared to single stars. This suggests that the effects of binary evolution should be considered when modeling the CMDs and stellar populations of star clusters and galaxies.
文摘Semi solid metallurgy offers distinct advantages over other near-net-shape manufacturing processes. By this process, components are produced from slurry kept at a temperature between the solidus and the liquidus isotherms, resulting in breakdown of the dendritic structure. A new structure in which the morphology of the crystals of the primary phase is globular evolves. In this present paper, the importance of globular structure is identified. The theories of evolution of globular crystals in thixo–processing are identified and discussed.
基金Project(51575446) supported by the National Natural Science Foundation of ChinaProject(2016JQ5070) supported by the Natural Science Basis Research Plan of Shaanxi Province,China+1 种基金Project(2017KJXX-27) supported by the Youth Science and Technology New Star Plan of Shaanxi Province,ChinaProject(3102017AX003) supported by the Fundamental Research Funds for the Central Universities,China
文摘The sensitivity analysis functions on globularized fraction ofαlamellae were established using a physically-based microstructure model and gradient method.These functions were applied to the sensitivity analysis on globularized fraction ofαlamellae in TC17 alloy.The material constants in these functions are determined using the genetic algorithm-based objective optimization technique.The globularized fraction ofαlamellae during isothermal compression of TC17 alloy was quantitatively analyzed based on scanning electron microscopy(SEM)observation.The results show thatαlamellae mostly change to equiaxedαgrains at a deformation temperature of 1083 K,a strain rate of 0.01 s^-1 and a strain of 1.2.The globularized fraction decreases with increasing strain rate because lower strain rate provides enough time for the spheroidization.The effect of deformation temperature on the globularized fraction is controlled by the strain rate.And,the predicted derivations of globularized fraction with respect to processing parameters show good agreement with the experimental values.
基金supported in part by the National Key R&D Program of China under Grant No.2018YFA0404204the National Natural Science Foundation of China Nos.12163006 and 12233006+1 种基金the Basic Research Program of Yunnan Province No.202201AT070137the joint foundation of Department of Science and Technology of Yunnan Province and Yunnan University No.202201BF070001-020。
文摘In this paper,~12 yr long-term Pass 8 data from Fermi Large Area Telescope for the 157 globular clusters are carefully re-analyzed.Besides the 31 globular clusters reported in the fourth Fermi Large Area Telescope catalog Data Release 2,NGC 1851 is identified as a gamma-ray emitter and the significant gamma-ray emissions from NGC 6715 and NGC 6723 are detected.Especially NGC 6715 is located at a distance of 26.8 kpc,so far it is the farthest globular cluster detected in gamma-rays.A detailed analysis for these three globular clusters has been performed,but their gamma-ray pulsation emissions or flux variabilities are not found.The numbers of millisecond pulsars(MSPs)in these globular clusters are estimated under the assumption that each MSP inside globular clusters emits a similar amount of gamma-rays.Some possible origins of gamma-ray emission from globular clusters,such as MSPs,pulsar binary systems and/or dark matter,are discussed.
基金Project supported by the National Natural Science Foundation of China (Grant No 10747160)SRF for ROCS, SEM (Grant No [2008]890)
文摘The character of forming long-range contacts affects the three-dimensional structure of globular proteins deeply. As the different ability to form long-range contacts between 20 types of amino acids and 4 categories of globular proteins, the statistical properties are thoroughly discussed in this paper. Two parameters NC and ND are defined to confine the valid residues in detail. The relationship between hydrophobieity scales and valid residue percentage of each amino acid is given in the present work and the linear functions are shown in our statistical results. It is concluded that the hydrophobicity scale defined by chemical derivatives of the amino acids and nonpolar phase of large unilamellar vesicle membranes is the most effective technique to characterise the hydrophobic behavior of amino acid residues. Meanwhile, residue percentage Pi and sequential residue length Li of a certain protein i are calculated under different conditions. The statistical results show that the average value of Pi as well as Li of all-α proteins has a minimum among these 4 classes of globular proteins, indicating that all-α proteins are hardly capable of forming long-range contacts one by one along their linear amino acid sequences. All-β proteins have a higher tendency to construct long-range contacts along their primary sequences related to the secondary configurations, i.e. parallel and anti-parallel configurations of/3 sheets. The investigation of the interior properties of globular proteins give us the connection between the three-dimensional structure and its primary sequence data or secondary configurations, and help us to understand the structure of protein and its folding process well.
基金Supported by the National Natural Science Foundation of China.
文摘We aim to retrieve ghost streams under the assumption that all the globular clusters in our Galaxy were formed in very early merge events. Our results are based on two speculations： that the specific energy and angular momentum of the globular clusters after merge are not changed in the course of evolution and that the globular clusters with a common origin would stay in the same orbit plane as the parent galaxy. After taking into account the apogalacticum distance of the orbits, we suggest with some Confidence five possible streams. The number of streams is consistent with the previous results. Three of the four well established members of the Sagittadus stream were found to be in one of our streams. Several other globular clusters in our result were also thought to come from accretion by previous researchers. The orbital parameters of the streams are derived, which provide a way to test whether these streams are true with the help of more accurate measurement of proper motions of the globular clusters.
基金This work was supported by the National Natural Science Foundation of China (Nos. 29874012, 20174036, and20274040), and the Natural Science Foundation of Zhejiang Province (10102) and Science Technology Development Plan of Wenzhou City (S2002A014).
文摘The analysis of residue-residue contacts in protein structures can shed some light on our understanding of the folding and stability of proteins. In this paper, we study the statistical properties of long-range and short-range residue- residue contacts of 91 globular proteins using CSU software and analyze the importance of long-range contacts in globular protein structure. There are many short-range and long-range contacts in globular proteins, and it is found that the average number of long-range contacts per residue is 5.63 and the percentage of residue-residue contacts which are involved in long- range ones is 59.4%. In more detail, the distribution of long-range contacts in different residue intervals is investigated and it is found that the residues occurring in the interval range of 4-10 residues apart in the sequence contribute more long-range contacts to the stability of globular protein. The number of long-range contacts per residue, which is a measure of ability to form residue-residue contacts, is also calculated for 20 different amino acid residues. It is shown that hydrophobic residues (including Leu, Val, He, Met, Phe, Tyr, Cys and Trp) having a large number of long-range contacts easily form long-range contacts, while the hydrophilic amino acids (including Ala, Gly, Thr, His, Glu, Gln, Asp, Asn, Lys, Ser, Arg, and Pro) form long-range contacts with more difficulty. The relationship between the Fauchere-Pliska hydrophobicity scale (FPH) and the number of short-range and long-range contacts per residue for 20 amino acid residues is also studied. An approximately linear relationship between the Fauchere-Pliska hydrophobicity scale (FPH) and the number of long-range contacts per residue CL, is found and can be expressed as CL = a + b × FPH where a = 5.04 and b = 1.23. These results can help us to understand the role of residue-residue contacts in globular protein structure.
基金Supported by the National Natural Science Foundation of China
文摘The sixth Data Release （DR6） of the Sloan Digital Sky Survey （SDSS） provides more photometric regions, new features and more accurate data around globular cluster Palomar 5. A new method, Back Propagation Neural Network （BPNN）, is used to estimate the cluster membership probability in order to detect its tidal tails. Cluster and field stars, used for training the networks, are extracted over a 40 × 20 deg^2 field by color-magnitude diagrams （CMDs）. The best BPNNs with two hidden layers and a Levenberg-Marquardt （LM） training algorithm are determined by the chosen cluster and field samples. The membership probabilities of stars in the whole field are obtained with the BPNNs, and contour maps of the probability distribution show that a tail extends .5.42° to the north of the cluster and another tail extends 3.77° to the south. The tails are similar to those detected by Odenkirchen et al., but no more debris from the cluster is found to the northeast in the sky. The radial density profiles are investigated both along the tails and near the cluster center. Quite a few substructures are discovered in the tails. The number density profile of the cluster is fitted with the King model and the tidal radius is determined as 14.28＇. However, the King model cannot fit the observed profile at the outer regions （R 〉 8＇） because of the tidal tails generated by the tidal force. Luminosity functions of the cluster and the tidal tails are calculated, which confirm that the tails originate from Palomar 5.
