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
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
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 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
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 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
The effects of initial microstructure on the flow stress, strain rate sensitivity （m）, strain hardening exponent （n）, apparent activation energy （Q） for deformation of Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy were investiga...The effects of initial microstructure on the flow stress, strain rate sensitivity （m）, strain hardening exponent （n）, apparent activation energy （Q） for deformation of Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy were investigated using isothermal compression tests. Results show that the alloy with Widmanst-tten alpha plates shows a higher peak stress and flow softening. Additionally, the alloy with equiaxed primary alpha exhibits an early yield drop at or above 810 ℃ and at strain rates of 0.1-5.0 s^-1. In the strain range of 0.5-0.7,m of the alloy with equiaxed primary alpha is found to be larger at 0.01 s^-1 and lower deformation temperatures. This phenomenon could be reasonably explained based on the microstructure evolution. The strain has a significant effect onn of the alloy with Widmanst-tten alpha plates, which is attributed to platelet bending/kinking and dynamic globularization ofα phase. In the strain range of 0.15-0.55,Q of the alloy with Widmanst-tten alpha plates is larger.展开更多
The inner Milky Way disk globular cluster NGC 6362 appears to exhibit tidal tails composed of stars that have proper motions and positions in the color–magnitude diagram similar to those of cluster stars. Because rec...The inner Milky Way disk globular cluster NGC 6362 appears to exhibit tidal tails composed of stars that have proper motions and positions in the color–magnitude diagram similar to those of cluster stars. Because recent results seem also to show that these stars are distributed across the regions least affected by interstellar absorption and reproduce the observed composite star field density map, we carried out a detailed spectroscopic analysis of a number of chemical element abundances of tidal tail star candidates in order to investigate the relationship between them and NGC 6362. From European Southern Observatory's VLT@FLAMES spectra we found that the red giant branch stars selected as the cluster's tidal tail stars neither have overall metallicities nor abundances of Mg, Ca, Sc, Ti, Cr, Ni and Ba similar to the cluster's ones. Moreover, they are mainly alike to stars that belong to the Milky Way thick disk, some of them could be part of the thin disk and a minor percentage could belong to the Milky Way halo star population. On the other hand, since the resulting radial velocities do not exhibit a distribution function similar to that of the cluster's stars, we concluded that looking for kinematic properties similar to those of the cluster would not seem to be as suitable of an approach for selecting the cluster's tidal tail stars as previously thought.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
We report the discovery of an isolated millisecond pulsar M15O(J2129+1210O)from the globular cluster M15(NGC 7078)with a period of 11.06686 ms and a dispersion measure of~67.44 cm^(-3)pc.Its spin period is so close to...We report the discovery of an isolated millisecond pulsar M15O(J2129+1210O)from the globular cluster M15(NGC 7078)with a period of 11.06686 ms and a dispersion measure of~67.44 cm^(-3)pc.Its spin period is so close to the 10th harmonic of the bright pulsar M15A(~11.06647 ms)that it was missed in a previous pulsar search.We suggest adding the spectrum in the pulsar candidate diagnostic plot to identify new signals near the harmonics.M15O has the first spin frequency derivative and the second spin frequency derivative,being 1.79191(5)×10^(-14)Hz s^(-1)and 3.3133(6)×10^(-23)Hz s^(-2),respectively.Its projected distance from the optical center of M15 is the closest among all the pulsars in M15.The origin can be something from the center of the massive and core-collapsed globular cluster M15.展开更多
We present a new two-dimensional(2D)map of total Galactic extinction,Av,across the entire dust half-layer from the Sun to extragalactic space for Galactic latitudes|b|>13°,as well as a three-dimensional(3D)map...We present a new two-dimensional(2D)map of total Galactic extinction,Av,across the entire dust half-layer from the Sun to extragalactic space for Galactic latitudes|b|>13°,as well as a three-dimensional(3D)map of Av within 2 kpc of the Sun.These maps are based on A_(V)and distance estimates derived from a data set,which utilizes Gaia Data Release 3 parallaxes and multi-band photometry for nearly 100 million dwarf stars.We apply our own corrections to account for significant systematics in this data set.Our 2D map achieves an angular resolution of6'.1,while the 3D map offers a transverse resolution of 3.56 pc—corresponding to variable angular resolution depending on distance—and a radial resolution of 50 pc.In constructing these maps,we pay particular attention to the solar neighborhood(within 200 pc)and to high Galactic latitudes.The 3D map predicts Av from the Sun to any extended object within the Galactic dust layer with an accuracy ofσ(A_(V))=0.1 mag.The 2D map provides Av estimates for the entire dust half-layer up to extragalactic distances with an accuracy ofσ(A_(V))=0.07 mag.We provide A_(V)estimates from our maps for various classes of extended celestial objects with angular size primarily in the range of 2′-40′,including 19,809 galaxies and quasars,170 Galactic globular clusters,458 open clusters,and several hundred molecular clouds from two lists.We also present extinction values for 8293 TypeⅠa supernovae.Comparison of our extinction estimates with those from previous maps and literature sources reveals systematic differences,indicating large-scale spatial variations in the extinction law and suggesting that earlier 2D reddening maps based on infrared dust emission tend to underestimate low extinction values.展开更多
The evolution of coordination betweenαandβphases for a two-phase titanium alloy was investigated.For this purpose,hot compression and heat treatment under different conditions were carried out.The results show that ...The evolution of coordination betweenαandβphases for a two-phase titanium alloy was investigated.For this purpose,hot compression and heat treatment under different conditions were carried out.The results show that the ability of coordinated deformation betweenαandβphases can influence uniformity of microstructure evolution.Specifically,αphase maintains the lamellar structure andβphase has a low degree of recrystallization when the ability of coordinated deformation is good.In this case,αandβphases still maintain the BOR(Burgers orientation relationship),and their interface relationship is not destroyed even at large deformation.Both of the deformation extent ofαlamellae and recrystallization degree ofβphase increase with the decline of ability of coordinated deformation.Theαphase only maintains the BOR withβphase on one side,while the uncoordinated rotation with theβphase on the other side occurs within 10°.Theαandβphases rotate asynchronously when ability of coordinated deformation is poor.The degree of interface dislocation increases,andαandβphases deviate from the BOR.展开更多
The hot deformation characteristics of the Ti-5.7Al-2.1Sn-3.9Zr-2Mo-0.1Si(Ti-6242S)alloy with an acicular starting microstructure were analyzed using processing map.The uniaxial hot compression tests were performed at...The hot deformation characteristics of the Ti-5.7Al-2.1Sn-3.9Zr-2Mo-0.1Si(Ti-6242S)alloy with an acicular starting microstructure were analyzed using processing map.The uniaxial hot compression tests were performed at temperatures ranging from 850 to 1000℃and at strain rates of 0.001-1 s-1.The developed processing map was used to determine the safe and unsafe deformation conditions of the alloy in association with the microstructural evolution by SEM and OM.It was recognized that the flow stress revealed differences in flow softening behavior by deformation at 1000℃compared to the lower deformation temperatures,which was attributed to microstructural changes.The processing map developed for typical strain of 0.7 in two-phase field exhibited high efficiency value of power dissipation of about 55%at 950℃and 0.001 s-1,basically due to extensive globularization.An increase in strain rate and a decrease in temperature resulted in a decrease in globularization ofαlamellae,whileαlamellar kinking increased.Eventually,the instability domain of flow behavior was identified in the temperature range of 850-900℃and at the strain rate higher than 0.01 s-1 reflecting the flow localization and adiabatic shear banding.By considering the power efficiency domains and the microstructural observations,the deformation in the temperature range of 950-1000℃and strain rate range of 0.001-0.01 s-1 was desirable leading to high efficiencies.It was realized that(950℃,0.001 s-1)was the optimum deformation condition for the alloy.展开更多
Microstructural development in hot working of TA15titanium alloy with primary stripαstructure was investigated withthe aim to globularizeαstrips.Results show that the mechanisms of morphology transformation are the ...Microstructural development in hot working of TA15titanium alloy with primary stripαstructure was investigated withthe aim to globularizeαstrips.Results show that the mechanisms of morphology transformation are the same to the spheroidizationmechanisms of lamellar structure.Boundary splitting and termination migration are more important than coarsening due to the largesize of stripα.Theαstrips are stable in annealing due to the unfavorable geometrical orientation of intra-αboundaries,the largethickness of strip and the geometrical stability ofαparticles.Predeformation and low speed deformation accelerate globularization ofαstrips in the following ways:direct changing of particle shape,promotion of boundary splitting and termination migration byincreasing high angle grain boundaries and interfacial area,promotion of coarsening by forming dislocation structures.Largepredeformation combined with high temperature annealing is a feasible way to globularize stripα.展开更多
TC21 titanium alloy,as an important metal to fabricate the aircraft structural components,has attracted great attentions recently.A TC21 titanium alloy with widmanst?tten structure was isothermally compressed.Based on...TC21 titanium alloy,as an important metal to fabricate the aircraft structural components,has attracted great attentions recently.A TC21 titanium alloy with widmanst?tten structure was isothermally compressed.Based on the microstructure observation,the evolution of initialβgrain,Grain Boundaryαphase(α;),lamellar a and interlayeredβwas systematically investigated.The results showed that,with the increasing of height reduction,theα;underwent an evolution process from bending/kinking to breaking inducing the corresponding blurring of initial coarse b grain outline.Meanwhile,a significant phase transformation from a to b took place at the terminations of brokenα;.The evolution of lamellarαand interlayeredβin the colony was closely related to their deformation compatibility.In the a colony,the interlayered b experienced a larger deformation amount than lamellarα.The higher distortion energy promoted the occurrence of Dynamic Recovery(DRV)and Dynamic Recrystallization(DRX)to generate many Low Angle Boundaries(LABs)and High Angle Boundaries(HABs)in interlayered b,which induced an apparent grain refinement of b phase.On the contrary,the lower distortion energy and low deformation temperature suppressed the occurrence of DRV/DRX and restrained the globularization of lamellarα.Furthermore,the microstructure observation clearly revealed that the shearing separation mechanism dominated the evolution of the a phase from lamellar to short bar-like morphology.展开更多
C1q is the first subcomponent of classical pathway in the complement system and a major link between innate and acquired immunities.The globular(gC1q)domain similar with C1q was also found in many non-complement C1q-d...C1q is the first subcomponent of classical pathway in the complement system and a major link between innate and acquired immunities.The globular(gC1q)domain similar with C1q was also found in many non-complement C1q-domain-containing(C1qDC)proteins which have similar crystal structure to that of the multifunctional tumor necrosis factor(TNF)ligand family,and also have diverse functions.In this study,we identified a total of 52 independent gene sequences encoding C1q-domain-containing proteins through comprehensive searches of zebrafish genome,cDNA and EST databases.In comparison to 31 orthologous genes in human and different numbers in other species,a significant selective pressure was suggested during vertebrate evolution.Domain organization of C1q-domain-containing(C1qDC)proteins mainly includes a leading signal peptide,a collagen-like region of variable length,and a C-terminal C1q domain.There are 11 highly conserved residues within the C1q domain,among which 2 are invariant within the zebrafish gene set.A more extensive database searches also revealed homologous C1qDC proteins in other vertebrates,invertebrates and even bacterium,but no homologous sequences for encoding C1qDC proteins were found in many species that have a more recent evolutionary history with zebrafish.Therefore,further studies on C1q-domain-containing genes among different species will help us understand evolutionary mechanism of innate and acquired immunities.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
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 (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.
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Projects(5120531851275416)supported by the National Natural Science Foundation of ChinaProject(2012KJ02002)supported by the Innovation Fund of Science and Technology in Northwestern Polytechnical University,China
文摘The effects of initial microstructure on the flow stress, strain rate sensitivity （m）, strain hardening exponent （n）, apparent activation energy （Q） for deformation of Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy were investigated using isothermal compression tests. Results show that the alloy with Widmanst-tten alpha plates shows a higher peak stress and flow softening. Additionally, the alloy with equiaxed primary alpha exhibits an early yield drop at or above 810 ℃ and at strain rates of 0.1-5.0 s^-1. In the strain range of 0.5-0.7,m of the alloy with equiaxed primary alpha is found to be larger at 0.01 s^-1 and lower deformation temperatures. This phenomenon could be reasonably explained based on the microstructure evolution. The strain has a significant effect onn of the alloy with Widmanst-tten alpha plates, which is attributed to platelet bending/kinking and dynamic globularization ofα phase. In the strain range of 0.15-0.55,Q of the alloy with Widmanst-tten alpha plates is larger.
基金Based on observations collected at the European Southern Observatory under ESO program(s)113.2661.001.
文摘The inner Milky Way disk globular cluster NGC 6362 appears to exhibit tidal tails composed of stars that have proper motions and positions in the color–magnitude diagram similar to those of cluster stars. Because recent results seem also to show that these stars are distributed across the regions least affected by interstellar absorption and reproduce the observed composite star field density map, we carried out a detailed spectroscopic analysis of a number of chemical element abundances of tidal tail star candidates in order to investigate the relationship between them and NGC 6362. From European Southern Observatory's VLT@FLAMES spectra we found that the red giant branch stars selected as the cluster's tidal tail stars neither have overall metallicities nor abundances of Mg, Ca, Sc, Ti, Cr, Ni and Ba similar to the cluster's ones. Moreover, they are mainly alike to stars that belong to the Milky Way thick disk, some of them could be part of the thin disk and a minor percentage could belong to the Milky Way halo star population. On the other hand, since the resulting radial velocities do not exhibit a distribution function similar to that of the cluster's stars, we concluded that looking for kinematic properties similar to those of the cluster would not seem to be as suitable of an approach for selecting the cluster's tidal tail stars as previously thought.
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.
基金supported by the National Key R&D Program of China No.2022YFC2205202,No.2020SKA0120100the National Natural Science Foundation of China(NSFC,grant Nos.12373032,12003047,11773041,U2031119,12173052,and 12173053)+2 种基金supported by the Youth Innovation Promotion Association of CAS(id.2018075,Y2022027 and 2023064)the CAS“Light of West China”Programsupported by the Science and Technology Program of Guizhou Province under project No.QKHPTRC-ZDSYS[2023]003 and QKHFQ[2023]003。
文摘We report the discovery of an isolated millisecond pulsar M15O(J2129+1210O)from the globular cluster M15(NGC 7078)with a period of 11.06686 ms and a dispersion measure of~67.44 cm^(-3)pc.Its spin period is so close to the 10th harmonic of the bright pulsar M15A(~11.06647 ms)that it was missed in a previous pulsar search.We suggest adding the spectrum in the pulsar candidate diagnostic plot to identify new signals near the harmonics.M15O has the first spin frequency derivative and the second spin frequency derivative,being 1.79191(5)×10^(-14)Hz s^(-1)and 3.3133(6)×10^(-23)Hz s^(-2),respectively.Its projected distance from the optical center of M15 is the closest among all the pulsars in M15.The origin can be something from the center of the massive and core-collapsed globular cluster M15.
基金financial support from the Russian Science Foundation(grant No.20-72-10052)。
文摘We present a new two-dimensional(2D)map of total Galactic extinction,Av,across the entire dust half-layer from the Sun to extragalactic space for Galactic latitudes|b|>13°,as well as a three-dimensional(3D)map of Av within 2 kpc of the Sun.These maps are based on A_(V)and distance estimates derived from a data set,which utilizes Gaia Data Release 3 parallaxes and multi-band photometry for nearly 100 million dwarf stars.We apply our own corrections to account for significant systematics in this data set.Our 2D map achieves an angular resolution of6'.1,while the 3D map offers a transverse resolution of 3.56 pc—corresponding to variable angular resolution depending on distance—and a radial resolution of 50 pc.In constructing these maps,we pay particular attention to the solar neighborhood(within 200 pc)and to high Galactic latitudes.The 3D map predicts Av from the Sun to any extended object within the Galactic dust layer with an accuracy ofσ(A_(V))=0.1 mag.The 2D map provides Av estimates for the entire dust half-layer up to extragalactic distances with an accuracy ofσ(A_(V))=0.07 mag.We provide A_(V)estimates from our maps for various classes of extended celestial objects with angular size primarily in the range of 2′-40′,including 19,809 galaxies and quasars,170 Galactic globular clusters,458 open clusters,and several hundred molecular clouds from two lists.We also present extinction values for 8293 TypeⅠa supernovae.Comparison of our extinction estimates with those from previous maps and literature sources reveals systematic differences,indicating large-scale spatial variations in the extinction law and suggesting that earlier 2D reddening maps based on infrared dust emission tend to underestimate low extinction values.
基金financial supports from the National Natural Science Foundation of China (No. 51905436)the Natural Science Foundation of Shaanxi Province, China (No. 2020JQ-156)。
文摘The evolution of coordination betweenαandβphases for a two-phase titanium alloy was investigated.For this purpose,hot compression and heat treatment under different conditions were carried out.The results show that the ability of coordinated deformation betweenαandβphases can influence uniformity of microstructure evolution.Specifically,αphase maintains the lamellar structure andβphase has a low degree of recrystallization when the ability of coordinated deformation is good.In this case,αandβphases still maintain the BOR(Burgers orientation relationship),and their interface relationship is not destroyed even at large deformation.Both of the deformation extent ofαlamellae and recrystallization degree ofβphase increase with the decline of ability of coordinated deformation.Theαphase only maintains the BOR withβphase on one side,while the uncoordinated rotation with theβphase on the other side occurs within 10°.Theαandβphases rotate asynchronously when ability of coordinated deformation is poor.The degree of interface dislocation increases,andαandβphases deviate from the BOR.
文摘The hot deformation characteristics of the Ti-5.7Al-2.1Sn-3.9Zr-2Mo-0.1Si(Ti-6242S)alloy with an acicular starting microstructure were analyzed using processing map.The uniaxial hot compression tests were performed at temperatures ranging from 850 to 1000℃and at strain rates of 0.001-1 s-1.The developed processing map was used to determine the safe and unsafe deformation conditions of the alloy in association with the microstructural evolution by SEM and OM.It was recognized that the flow stress revealed differences in flow softening behavior by deformation at 1000℃compared to the lower deformation temperatures,which was attributed to microstructural changes.The processing map developed for typical strain of 0.7 in two-phase field exhibited high efficiency value of power dissipation of about 55%at 950℃and 0.001 s-1,basically due to extensive globularization.An increase in strain rate and a decrease in temperature resulted in a decrease in globularization ofαlamellae,whileαlamellar kinking increased.Eventually,the instability domain of flow behavior was identified in the temperature range of 850-900℃and at the strain rate higher than 0.01 s-1 reflecting the flow localization and adiabatic shear banding.By considering the power efficiency domains and the microstructural observations,the deformation in the temperature range of 950-1000℃and strain rate range of 0.001-0.01 s-1 was desirable leading to high efficiencies.It was realized that(950℃,0.001 s-1)was the optimum deformation condition for the alloy.
基金Projects(51205317,51575449) supported by the National Natural Science Foundation of ChinaProject(3102015AX004) supported by the Fundamental Research Funds for the Central Universities,ChinaProject(104-QP-2014) supported by the Research Fund of the State Key Laboratory of Solidification Processing,China
文摘Microstructural development in hot working of TA15titanium alloy with primary stripαstructure was investigated withthe aim to globularizeαstrips.Results show that the mechanisms of morphology transformation are the same to the spheroidizationmechanisms of lamellar structure.Boundary splitting and termination migration are more important than coarsening due to the largesize of stripα.Theαstrips are stable in annealing due to the unfavorable geometrical orientation of intra-αboundaries,the largethickness of strip and the geometrical stability ofαparticles.Predeformation and low speed deformation accelerate globularization ofαstrips in the following ways:direct changing of particle shape,promotion of boundary splitting and termination migration byincreasing high angle grain boundaries and interfacial area,promotion of coarsening by forming dislocation structures.Largepredeformation combined with high temperature annealing is a feasible way to globularize stripα.
基金supported by National Natural Science Foundation of China(No.51971046)Fundamental Research Funds for the Central Universities,China(No.2020CDJGFCL005)。
文摘TC21 titanium alloy,as an important metal to fabricate the aircraft structural components,has attracted great attentions recently.A TC21 titanium alloy with widmanst?tten structure was isothermally compressed.Based on the microstructure observation,the evolution of initialβgrain,Grain Boundaryαphase(α;),lamellar a and interlayeredβwas systematically investigated.The results showed that,with the increasing of height reduction,theα;underwent an evolution process from bending/kinking to breaking inducing the corresponding blurring of initial coarse b grain outline.Meanwhile,a significant phase transformation from a to b took place at the terminations of brokenα;.The evolution of lamellarαand interlayeredβin the colony was closely related to their deformation compatibility.In the a colony,the interlayered b experienced a larger deformation amount than lamellarα.The higher distortion energy promoted the occurrence of Dynamic Recovery(DRV)and Dynamic Recrystallization(DRX)to generate many Low Angle Boundaries(LABs)and High Angle Boundaries(HABs)in interlayered b,which induced an apparent grain refinement of b phase.On the contrary,the lower distortion energy and low deformation temperature suppressed the occurrence of DRV/DRX and restrained the globularization of lamellarα.Furthermore,the microstructure observation clearly revealed that the shearing separation mechanism dominated the evolution of the a phase from lamellar to short bar-like morphology.
基金Acknowledgements This work was supported by the National Major Basic Research Program(No.2004CB117401)by the National Natural Science Foundation of China(No.90408013).
文摘C1q is the first subcomponent of classical pathway in the complement system and a major link between innate and acquired immunities.The globular(gC1q)domain similar with C1q was also found in many non-complement C1q-domain-containing(C1qDC)proteins which have similar crystal structure to that of the multifunctional tumor necrosis factor(TNF)ligand family,and also have diverse functions.In this study,we identified a total of 52 independent gene sequences encoding C1q-domain-containing proteins through comprehensive searches of zebrafish genome,cDNA and EST databases.In comparison to 31 orthologous genes in human and different numbers in other species,a significant selective pressure was suggested during vertebrate evolution.Domain organization of C1q-domain-containing(C1qDC)proteins mainly includes a leading signal peptide,a collagen-like region of variable length,and a C-terminal C1q domain.There are 11 highly conserved residues within the C1q domain,among which 2 are invariant within the zebrafish gene set.A more extensive database searches also revealed homologous C1qDC proteins in other vertebrates,invertebrates and even bacterium,but no homologous sequences for encoding C1qDC proteins were found in many species that have a more recent evolutionary history with zebrafish.Therefore,further studies on C1q-domain-containing genes among different species will help us understand evolutionary mechanism of innate and acquired immunities.
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.
