Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening pa...Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening particles also deteriorates the processability and it is of great importance to establish accurate processing maps to guide the thermomechanical processes to enhance the formability.In this study,we performed particle swarm optimization-based back propagation artificial neural network model to predict the high temperature flow behavior of 0.25wt%Al2O3 particle-reinforced Cu alloys,and compared the accuracy with that of derived by Arrhenius-type constitutive model and back propagation artificial neural network model.To train these models,we obtained the raw data by fabricating ODS Cu alloys using the internal oxidation and reduction method,and conducting systematic hot compression tests between 400 and800℃with strain rates of 10^(-2)-10 S^(-1).At last,processing maps for ODS Cu alloys were proposed by combining processing parameters,mechanical behavior,microstructure characterization,and the modeling results achieved a coefficient of determination higher than>99%.展开更多
High-density stacking faults(SFs)were introduced into a novel Ni-Co-based superalloy through warm rolling at 300-500°C,and the effects of SFs on its tensile properties at intermediate temperatures(650 and 750...High-density stacking faults(SFs)were introduced into a novel Ni-Co-based superalloy through warm rolling at 300-500°C,and the effects of SFs on its tensile properties at intermediate temperatures(650 and 750°C)were investigated.The results indicated that all warm rolled specimens have high-density SFs and Lomer-Cottrell locks compared with the initial specimens.Meanwhile,the simultaneous improvement of intermediate-temperature strength and ductility of alloys can be achieved by high-density SFs.In particular,the specimen rolled at 300°C exhibited a superior combination of high strength(yield and ultimate tensile strengths of(1311±18)and(1462±25)MPa respectively at 650°C,and(1180±17)and(1293±15)MPa respectively at 750°C)and high fracture elongation((26.7±2.5)%at 650°C and(10.7±1.3)%at 750°C).The high strengths and facture elongations of all warm-rolled specimens were primarily attributed to the interaction of pre-existingγ′phases,high-density SFs and Lomer-Cottrell locks with dislocations,as well as to the formation of high-density deformation nano-twins during tensile loading.展开更多
Diffusion of solutes significantly affects the coarsening rate of γ'precipitates in precipitation-hardened high entropy alloys(PH-HEAs).In this work,we systematically study the refractory solutes M(Hf,Nb,Ta,Mo,W,...Diffusion of solutes significantly affects the coarsening rate of γ'precipitates in precipitation-hardened high entropy alloys(PH-HEAs).In this work,we systematically study the refractory solutes M(Hf,Nb,Ta,Mo,W,Re,Ru)diffusion in face-centered-cubic(FCC)NiCoFeCr lattice through a combination of first-principles calculations,diffusion couples,and coarsening of γ'precipitates experiments.Our calculations reveal that there exists a stronger negative correlation between solute diffusivity and Young’s modulus than between solute diffusivity and atomic size;i.e.,the higher the Young’s modulus,the more difficult solute diffusion is.Based on the electronic structure analysis,the underlying origins for such a relation-ship could be ascribed to the fact that solutes with high Young’s modulus have stronger bonds with neighboring host atoms,less compressibility,and thus poor diffusivity.Afterwards,the main interdiffu-sion coefficients of three refractory elements with similar atomic sizes and increasing Young’s modulus,Mo,W,and Re,at 1150℃in(NiCoFeCr)_(92)Al_(3)Ti_(3)M_(2)are,in order of magnitude,D_(MoMo)^(Ni)>D_(WW)^(Ni)>D_(ReRe)^(Ni),as determined by the diffusion-couple experiments.Further investigations on the coarsening kinetics of precipitates confirmed the additions of refractory elements improve the coarsening resistance of γ'pre-cipitates in the order of Re>W>Mo.The trends in the diffusivity determined by experiment and simulation are in excellent agreement.More importantly,the Young’s modulus effect for the diffusion of refractory solutes in HEAs is also carefully analyzed and discussed.Our present findings will give new insights into future design of γ'-strengthened HEAs for high-temperature structural applications.展开更多
To develop high-hardness and high-strength lightweight high entropy alloys(LHEAs),a series of CoxAlNbTiVCr alloys were designed.The phase constitution,distribution,and crystal structure of the Laves phase in alloys ca...To develop high-hardness and high-strength lightweight high entropy alloys(LHEAs),a series of CoxAlNbTiVCr alloys were designed.The phase constitution,distribution,and crystal structure of the Laves phase in alloys can be altered by adjusting the composition of HEAs,which in turn influences their mechanical properties.Co_(x)AlNbTiVCr(x=0,0.5,1,1.5,and 2,atomic ratio percentage)LHEAs were designed and prepared to characterize the microstructure and tailor the mechanical properties.The introduction of Co changes the microstructure of LHEAs from a single B2 structure to a mixture dendrite structure,which consists of B2 phase,C14 and C15 Laves phase.Wherein the C14 and C15 Laves phases exhibit coupled growth.Several parameters including mixing enthalpy(ΔH_(mix)),valence electron concentration(VEC),atomic radius size(δ),mixing entropy(ΔS),and electronegativity difference(Δχ)are used to predict the formation of B2 and Laves phase in LHEAs.When the Co content increases from 0 to 1.5at.%,Laves phase volume fraction gradually increases,which leads to an enhancement in the compressive strength from 1,520.8 MPa to 1,844.4 MPa.Co_(1.5)AlNbTiVCr alloy exhibits the maximum Vickers hardness of 699.4 HV.The improvement of mechanical properties mainly originates from solid solution strengthening and second phase strengthening.展开更多
This paper reports a synergistic design of high-performance BCC high-entropy alloy based on the combined consideration of the principles of intrinsic ductility of elements,maximum atomic size difference for solid solu...This paper reports a synergistic design of high-performance BCC high-entropy alloy based on the combined consideration of the principles of intrinsic ductility of elements,maximum atomic size difference for solid solution strengthening and the valence electron concentration criterion for ductility.The single-phase BCC HfNbTaTiV alloy thus designed exhibited a high compressive yield strength of 1350 MPa and a high compressive ductility of>45%at the room temperature.This represents a 50%increase in yield strength relative to a HfNbTaTiZr alloy.This is attributed to the maximized solid solution strengthening effect caused by lattice distortion,which is estimated to be 1094 MPa.The alloy was also able to retain 53%of its yield strength and 77%of its ductility at 700℃.These properties are superior to those of most refractory BCC high-entropy alloys reported in the literature.展开更多
This work demonstrates the effectiveness of a cryogenic torsional pre-straining for significantly improving the cryogenic strength of an equiatomic CrCoNi alloy. The origin of this phenomenon is elucidated by various ...This work demonstrates the effectiveness of a cryogenic torsional pre-straining for significantly improving the cryogenic strength of an equiatomic CrCoNi alloy. The origin of this phenomenon is elucidated by various microstructural characterization tools, which shows that the sequential torsion and tension tests lead to the observed hierarchical microstructure through the activation of different twinning systems and stacking faults. This gives rise to the significant increase in the yield strength from 600 MPa to 1215 MPa,while the fracture strain changes from 68% to 48%. The current study reveals that the incorporation of nanotwins architecture by shear deformation may constitute a viable strategy to tune the mechanical performance and, in particular, to dramatically increase the strength while keeping a good ductility.展开更多
The radiation generated by nuclear reaction is harmful to human body and equipment,thus the radiation shielding materials that employ the shielding ability from neutron and gamma rays are the best candidates according...The radiation generated by nuclear reaction is harmful to human body and equipment,thus the radiation shielding materials that employ the shielding ability from neutron and gamma rays are the best candidates according to application situations and radiation sources.In this paper,the researches of metal-based neutron and gamma rays or multiple purpose shielding materials are systematically summarized,and the respective and principal problems of these materials with respect to shielding effectiveness and other performances,such as corrosion,mechanical properties,manufacture,etc.,are discussed.Finally,the prospect of shielding materials is outlined,which suggests that the development of highly efficient and multiply functional radiation shielding materials with good environmental compatibility is one of the future development trends.展开更多
As an attractive class of metallic materials,single-phase CrCoNi medium-entropy alloy(MEA)has drawn much attention recently regarding their deformation behaviors,but the dynamically mechanical responses of this alloy ...As an attractive class of metallic materials,single-phase CrCoNi medium-entropy alloy(MEA)has drawn much attention recently regarding their deformation behaviors,but the dynamically mechanical responses of this alloy at high strain rates remain less studied,especially coupled with extremely low temperatures.In this study,the dynamic deformation behaviors of this CrCoNi MEA were systematically investigated at room temperature(RT)of 298 K and liquid nitrogen temperature(LNT)of 77 K using the split Hopkinson pressure bar(SHPB).This alloy exhibited a combination of higher yield strength and stronger hardening rate upon dynamic compressive deformation when the loading conditions become much harsher(higher strain rate or lower temperature).Detailed microstructure analyses indicated that the strong strain hardening ability during dynamic deformation was mainly attributed to the continuous formation of nanoscale deformation twins.Furthermore,as loaded at LNT,multi-directional deformation twins were activated.Meanwhile,due to the interaction between Shockley partial dislocations and twin boundaries,large-sized deformation-induced FCC-HCP phase transformations at a micrometer scale were also observed within the grains,which not only accommodated the plasticity but also played an important role in improving the hardening capability owing to the appearance of newly generated interfaces.展开更多
In this paper, based on sparse representation classification and robust thought, we propose a new classifier, named MRSRC (Metasample Based Robust Sparse Representation Classificatier), for DNA microarray data classif...In this paper, based on sparse representation classification and robust thought, we propose a new classifier, named MRSRC (Metasample Based Robust Sparse Representation Classificatier), for DNA microarray data classification. Firstly, we extract Metasample from trainning sample. Secondly, a weighted matrix W is added to solve an l1-regular- ized least square problem. Finally, the testing sample is classified according to the sparsity coefficient vector of it. The experimental results on the DNA microarray data classification prove that the proposed algorithm is efficient.展开更多
The compression behaviors of iridium single crystals with different crystalline orientations were investigated by micropillar compression tests and molecular dynamics(MD) simulations.The results indicated that the def...The compression behaviors of iridium single crystals with different crystalline orientations were investigated by micropillar compression tests and molecular dynamics(MD) simulations.The results indicated that the deformation process of iridium single crystals with [100]and [110] orientations was presented as the stacking faults expansion and the formation of Lomer-Cottrell locks.And the occurrence of Lomer-Cottrell locks was considered as the interaction of stacking faults on {111} planes by MD simulations.The evolution of crystal structure in compression indicated that the Lomer-Cottrell locks might contribute to the large plastic deformation of iridium single crystals.Moreover,the deformation features in MD simulations showed that the elastic modulus(E) and yield stress(σ_(s)) of iridium single crystals were significantly influenced by the temperature.The elastic modulus and yield stress gradually decreased with an increased temperature for all orientations.Meanwhile,the single crystal with a closely spaced lattice structure exhibited superior mechanical properties at a same temperature.展开更多
Time-temperature-transformation(TTT)diagram plays a critical role in designing appropriate heat treatment process of steels by describing the relationship among holding time,temperature,and quantities of phase transfo...Time-temperature-transformation(TTT)diagram plays a critical role in designing appropriate heat treatment process of steels by describing the relationship among holding time,temperature,and quantities of phase transformation.Making predictions for TTT diagrams of new steel rapidly and accurately is therefore of much practical importance,especially for costly and time-consuming experimental determination.Here,TTT diagrams for carbon and low-alloy steels were predicted using machine learning methods.Five commonly used machine learning(ML)algorithms,backpropagation artificial neural network(BP network),LibSVM,k-nearest neighbor,Bagging,and Random tree,were adopted to select appropriate models for the prediction.The results illustrate that Bagging is the optimal model for the prediction of pearlite transformation and bainite transformation,and BP network is the optimal model for martensite transformation.Finally,the ML framework composed of Bagging and BP network models was applied to predict the entire TTT diagram.Additionally,the ML models show superior performance on the prediction of testing samples than the commercial software JMatPro.展开更多
Single-phase face-centered cubic(fcc)high/medium-entropy alloys(H/MEAs)exhibit a much higher tendency to form nanoscale deformation twins than conventional fcc metals with similar low stacking fault energies(SFEs).Thi...Single-phase face-centered cubic(fcc)high/medium-entropy alloys(H/MEAs)exhibit a much higher tendency to form nanoscale deformation twins than conventional fcc metals with similar low stacking fault energies(SFEs).This extraordinary propensity for nanotwin formation in H/MEAs cannot therefore be ex-plained by their low SFEs alone.Here,using in situ compression tests of CrCoNi in comparison with Ag nanopillars inside a transmission electron microscope,we found that in the CrCoNi MEA,a high density of nanoscale twins continuously formed with an average thickness of 4.6 nm.In contrast,for similar experiments on Ag with almost identical SFE,following the nucleation of a few twins,they could further thicken to above one hundred nanometers by twin boundary migration.Molecular dynamics calculations indicated that in the highly-concentrated CrCoNi solid solution,the magnitude of the energy barriers for nucleating a stacking fault as a twin precursor in the pristine lattice and for the thickening of an existing twin both span a wide range and largely overlap with each other.Therefore,twin thickening through successive addition of atomic layers is prone to discontinuation,giving way to the nucleation of new twins at other sites where a lower energy barrier is encountered for partial-dislocation mediated fault formation.展开更多
No direct comparison has been performed between different programmed cell death-1(PD-1)inhibitors for first-line treatment in patients with advanced non-small cell lung cancer(NSCLC).The feasibility of using PD-L1-exp...No direct comparison has been performed between different programmed cell death-1(PD-1)inhibitors for first-line treatment in patients with advanced non-small cell lung cancer(NSCLC).The feasibility of using PD-L1-expression-guided immunotherapy remains unknown.In this open-label,phase 2 study(NCT04252365),patients with advanced NSCLC without EGFR or ALK alterations were randomized(1:1)to receive sintilimab or pembrolizumab monotherapy(PD-L1 expression≥50%),or sintilimab or pembrolizumab plus platinum-based chemotherapy(PD-L1 expression<50%).The sample size was calculated by optimal two-stage design.The primary endpoint was the objective response rate(ORR).The study included 71 patients(sintilimab arms,n=35;pembrolizumab arms,n=36)and met its primary endpoint,with a confirmed ORR of 51.4%(18/35)in the sintilimab arms.The confirmed ORR(95%confidence interval)was 46.2%(19.2%,74.9%)and 42.9%(17.7%,71.1%)for patients treated with sintilimab and pembrolizumab monotherapy;and 54.5%(32.2%,75.6%)and 45.4%(24.4%,67.8%)for those treated with sintilimab-and pembrolizumab-based combination therapies.The median progression-free survival was6.9 versus 8.1 months for all sintilimab-treated versus all pembrolizumab-treated patients,respectively,in which it was 7.6 versus 11.0 months in monotherapy and 7.4 versus 7.1 months in combination therapies.The median overall survival was 14.9 versus 21.3 months for all sintilimab-treated versus all pembrolizumab-treated patients,respectively,in which it was 14.9 versus 22.6 months in monotherapy and 14.7 versus 17.3 months in combination therapies.Treatment-related adverse events were consistent with safety outcomes of monotherapy and combination therapy in previous phase III studies.However,the incidence of rash was higher with sintilimab than pembrolizumab monotherapy.This is the first prospective phase 2 study to directly compare two anti-PD-1 antibodies as first-line treatment in advanced NSCLC.Sintilimab was efficacious and well-tolerated irrespective of PD-L1 expression level in patients with advanced NSCLC and had similar efficacy and safety to pembrolizumab.展开更多
基金financial support of the National Natural Science Foundation of China(No.52371103)the Fundamental Research Funds for the Central Universities,China(No.2242023K40028)+1 种基金the Open Research Fund of Jiangsu Key Laboratory for Advanced Metallic Materials,China(No.AMM2023B01).financial support of the Research Fund of Shihezi Key Laboratory of AluminumBased Advanced Materials,China(No.2023PT02)financial support of Guangdong Province Science and Technology Major Project,China(No.2021B0301030005)。
文摘Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening particles also deteriorates the processability and it is of great importance to establish accurate processing maps to guide the thermomechanical processes to enhance the formability.In this study,we performed particle swarm optimization-based back propagation artificial neural network model to predict the high temperature flow behavior of 0.25wt%Al2O3 particle-reinforced Cu alloys,and compared the accuracy with that of derived by Arrhenius-type constitutive model and back propagation artificial neural network model.To train these models,we obtained the raw data by fabricating ODS Cu alloys using the internal oxidation and reduction method,and conducting systematic hot compression tests between 400 and800℃with strain rates of 10^(-2)-10 S^(-1).At last,processing maps for ODS Cu alloys were proposed by combining processing parameters,mechanical behavior,microstructure characterization,and the modeling results achieved a coefficient of determination higher than>99%.
基金supported by the Program for Hong Liu Excellent Young Scholars by Lanzhou University of Technology in 2023,the National Key Research and Development Program of China(No.2017YFA0700703)the Major Science and Technology Project of Gansu Province,China(Nos.22ZD6GA008,23ZDGC002,23ZDGA010)+1 种基金the Gansu Provincial Key Research and Development Program,China(No.20YF3GA041)the Special Fund of National Key Laboratory of Ni&Co Associated Minerals Resources Development and Comprehensive Utilization by Jinchuan Group Co.,Ltd.,China(No.GZSYS-KY-2022-012).
文摘High-density stacking faults(SFs)were introduced into a novel Ni-Co-based superalloy through warm rolling at 300-500°C,and the effects of SFs on its tensile properties at intermediate temperatures(650 and 750°C)were investigated.The results indicated that all warm rolled specimens have high-density SFs and Lomer-Cottrell locks compared with the initial specimens.Meanwhile,the simultaneous improvement of intermediate-temperature strength and ductility of alloys can be achieved by high-density SFs.In particular,the specimen rolled at 300°C exhibited a superior combination of high strength(yield and ultimate tensile strengths of(1311±18)and(1462±25)MPa respectively at 650°C,and(1180±17)and(1293±15)MPa respectively at 750°C)and high fracture elongation((26.7±2.5)%at 650°C and(10.7±1.3)%at 750°C).The high strengths and facture elongations of all warm-rolled specimens were primarily attributed to the interaction of pre-existingγ′phases,high-density SFs and Lomer-Cottrell locks with dislocations,as well as to the formation of high-density deformation nano-twins during tensile loading.
基金financially supported by the National Natural Science Foundation of China(No.51701061)the Natural Sci-ence Foundation of Hebei Province(No.E2019202059).
文摘Diffusion of solutes significantly affects the coarsening rate of γ'precipitates in precipitation-hardened high entropy alloys(PH-HEAs).In this work,we systematically study the refractory solutes M(Hf,Nb,Ta,Mo,W,Re,Ru)diffusion in face-centered-cubic(FCC)NiCoFeCr lattice through a combination of first-principles calculations,diffusion couples,and coarsening of γ'precipitates experiments.Our calculations reveal that there exists a stronger negative correlation between solute diffusivity and Young’s modulus than between solute diffusivity and atomic size;i.e.,the higher the Young’s modulus,the more difficult solute diffusion is.Based on the electronic structure analysis,the underlying origins for such a relation-ship could be ascribed to the fact that solutes with high Young’s modulus have stronger bonds with neighboring host atoms,less compressibility,and thus poor diffusivity.Afterwards,the main interdiffu-sion coefficients of three refractory elements with similar atomic sizes and increasing Young’s modulus,Mo,W,and Re,at 1150℃in(NiCoFeCr)_(92)Al_(3)Ti_(3)M_(2)are,in order of magnitude,D_(MoMo)^(Ni)>D_(WW)^(Ni)>D_(ReRe)^(Ni),as determined by the diffusion-couple experiments.Further investigations on the coarsening kinetics of precipitates confirmed the additions of refractory elements improve the coarsening resistance of γ'pre-cipitates in the order of Re>W>Mo.The trends in the diffusivity determined by experiment and simulation are in excellent agreement.More importantly,the Young’s modulus effect for the diffusion of refractory solutes in HEAs is also carefully analyzed and discussed.Our present findings will give new insights into future design of γ'-strengthened HEAs for high-temperature structural applications.
基金supported by the National Outstanding Youth Science Fund Project of National Natural Science Foundation of China(No.51825401)the China Postdoctoral Science Foundation(No.2023TQ0099).
文摘To develop high-hardness and high-strength lightweight high entropy alloys(LHEAs),a series of CoxAlNbTiVCr alloys were designed.The phase constitution,distribution,and crystal structure of the Laves phase in alloys can be altered by adjusting the composition of HEAs,which in turn influences their mechanical properties.Co_(x)AlNbTiVCr(x=0,0.5,1,1.5,and 2,atomic ratio percentage)LHEAs were designed and prepared to characterize the microstructure and tailor the mechanical properties.The introduction of Co changes the microstructure of LHEAs from a single B2 structure to a mixture dendrite structure,which consists of B2 phase,C14 and C15 Laves phase.Wherein the C14 and C15 Laves phases exhibit coupled growth.Several parameters including mixing enthalpy(ΔH_(mix)),valence electron concentration(VEC),atomic radius size(δ),mixing entropy(ΔS),and electronegativity difference(Δχ)are used to predict the formation of B2 and Laves phase in LHEAs.When the Co content increases from 0 to 1.5at.%,Laves phase volume fraction gradually increases,which leads to an enhancement in the compressive strength from 1,520.8 MPa to 1,844.4 MPa.Co_(1.5)AlNbTiVCr alloy exhibits the maximum Vickers hardness of 699.4 HV.The improvement of mechanical properties mainly originates from solid solution strengthening and second phase strengthening.
基金This work was financially supported by the Basic Science Center Program for Multiphase Evolution in Hyper-gravity of the National Natural Science Foundation of China(No.51988101)the National Natural Science Foundation of China(Nos.52071003,91860202,11604006)+4 种基金the Beijing Municipal Education Commission Project(Nos.PXM2020-014204-000021and PXM2019-014204-500032)the Beijing Outstanding Young Scientists Projects(No.BJJWZYJH01201910005018)the Beijing Natural Science Foundation(No.Z180014)the“111”project(No.DB18015)supported by the Australian Research Council(No.DP190102990)。
文摘This paper reports a synergistic design of high-performance BCC high-entropy alloy based on the combined consideration of the principles of intrinsic ductility of elements,maximum atomic size difference for solid solution strengthening and the valence electron concentration criterion for ductility.The single-phase BCC HfNbTaTiV alloy thus designed exhibited a high compressive yield strength of 1350 MPa and a high compressive ductility of>45%at the room temperature.This represents a 50%increase in yield strength relative to a HfNbTaTiZr alloy.This is attributed to the maximized solid solution strengthening effect caused by lattice distortion,which is estimated to be 1094 MPa.The alloy was also able to retain 53%of its yield strength and 77%of its ductility at 700℃.These properties are superior to those of most refractory BCC high-entropy alloys reported in the literature.
基金the financial support of the project from the National Natural Science Foundation of China(No.51601147)the Natural Science Foundation of Shaanxi Province(No.2017JQ5010)“the Fundamental Research Funds for the Central Universities”(No.3102016OQD048,3102017JC11001,3102017JC01003)
文摘This work demonstrates the effectiveness of a cryogenic torsional pre-straining for significantly improving the cryogenic strength of an equiatomic CrCoNi alloy. The origin of this phenomenon is elucidated by various microstructural characterization tools, which shows that the sequential torsion and tension tests lead to the observed hierarchical microstructure through the activation of different twinning systems and stacking faults. This gives rise to the significant increase in the yield strength from 600 MPa to 1215 MPa,while the fracture strain changes from 68% to 48%. The current study reveals that the incorporation of nanotwins architecture by shear deformation may constitute a viable strategy to tune the mechanical performance and, in particular, to dramatically increase the strength while keeping a good ductility.
文摘The radiation generated by nuclear reaction is harmful to human body and equipment,thus the radiation shielding materials that employ the shielding ability from neutron and gamma rays are the best candidates according to application situations and radiation sources.In this paper,the researches of metal-based neutron and gamma rays or multiple purpose shielding materials are systematically summarized,and the respective and principal problems of these materials with respect to shielding effectiveness and other performances,such as corrosion,mechanical properties,manufacture,etc.,are discussed.Finally,the prospect of shielding materials is outlined,which suggests that the development of highly efficient and multiply functional radiation shielding materials with good environmental compatibility is one of the future development trends.
基金supported by the National Natural Science Foundation of China(Grant No.12102363)the China National Funds for Distinguished Young Scientists(Grant No.12025205).
文摘As an attractive class of metallic materials,single-phase CrCoNi medium-entropy alloy(MEA)has drawn much attention recently regarding their deformation behaviors,but the dynamically mechanical responses of this alloy at high strain rates remain less studied,especially coupled with extremely low temperatures.In this study,the dynamic deformation behaviors of this CrCoNi MEA were systematically investigated at room temperature(RT)of 298 K and liquid nitrogen temperature(LNT)of 77 K using the split Hopkinson pressure bar(SHPB).This alloy exhibited a combination of higher yield strength and stronger hardening rate upon dynamic compressive deformation when the loading conditions become much harsher(higher strain rate or lower temperature).Detailed microstructure analyses indicated that the strong strain hardening ability during dynamic deformation was mainly attributed to the continuous formation of nanoscale deformation twins.Furthermore,as loaded at LNT,multi-directional deformation twins were activated.Meanwhile,due to the interaction between Shockley partial dislocations and twin boundaries,large-sized deformation-induced FCC-HCP phase transformations at a micrometer scale were also observed within the grains,which not only accommodated the plasticity but also played an important role in improving the hardening capability owing to the appearance of newly generated interfaces.
文摘In this paper, based on sparse representation classification and robust thought, we propose a new classifier, named MRSRC (Metasample Based Robust Sparse Representation Classificatier), for DNA microarray data classification. Firstly, we extract Metasample from trainning sample. Secondly, a weighted matrix W is added to solve an l1-regular- ized least square problem. Finally, the testing sample is classified according to the sparsity coefficient vector of it. The experimental results on the DNA microarray data classification prove that the proposed algorithm is efficient.
基金financially supported by the National Key R&D Program of China (No. 2017YFB0305503)the Joint Funds of the National Natural Science Foundation of China (No. U1202273)the National Natural Science Foundation of China (No. 51501075)。
文摘The compression behaviors of iridium single crystals with different crystalline orientations were investigated by micropillar compression tests and molecular dynamics(MD) simulations.The results indicated that the deformation process of iridium single crystals with [100]and [110] orientations was presented as the stacking faults expansion and the formation of Lomer-Cottrell locks.And the occurrence of Lomer-Cottrell locks was considered as the interaction of stacking faults on {111} planes by MD simulations.The evolution of crystal structure in compression indicated that the Lomer-Cottrell locks might contribute to the large plastic deformation of iridium single crystals.Moreover,the deformation features in MD simulations showed that the elastic modulus(E) and yield stress(σ_(s)) of iridium single crystals were significantly influenced by the temperature.The elastic modulus and yield stress gradually decreased with an increased temperature for all orientations.Meanwhile,the single crystal with a closely spaced lattice structure exhibited superior mechanical properties at a same temperature.
基金the financial support from the National Natural Science Foundation of China(Grant No.92060102).
文摘Time-temperature-transformation(TTT)diagram plays a critical role in designing appropriate heat treatment process of steels by describing the relationship among holding time,temperature,and quantities of phase transformation.Making predictions for TTT diagrams of new steel rapidly and accurately is therefore of much practical importance,especially for costly and time-consuming experimental determination.Here,TTT diagrams for carbon and low-alloy steels were predicted using machine learning methods.Five commonly used machine learning(ML)algorithms,backpropagation artificial neural network(BP network),LibSVM,k-nearest neighbor,Bagging,and Random tree,were adopted to select appropriate models for the prediction.The results illustrate that Bagging is the optimal model for the prediction of pearlite transformation and bainite transformation,and BP network is the optimal model for martensite transformation.Finally,the ML framework composed of Bagging and BP network models was applied to predict the entire TTT diagram.Additionally,the ML models show superior performance on the prediction of testing samples than the commercial software JMatPro.
基金supported by the National Natural Science Foundation of China(Nos.52231001,51971167,and 52031011)the Xi’an Science and Technology Plan(No.2017xasjl014)+4 种基金B.G.gratefully acknowledges the financial support of the project from the Ministry of Science and Technology of China(No.2017YFA0700703)the support by the National Natural Science Foundation of China(No.92060102)E.M.and J.D.acknowledge the support at CAID by XJTU.J.D.acknowledges support from the National Natural Science Foundation of China(No.12004294)the HPC platform of Xi’an Jiaotong Universitysupported by the Office of Science,Office of Basic Energy Sciences,Materials Sciences and Engineering Division,of the U.S.Department of Energy under Contract No.DE-AC02-05-CH11231.
文摘Single-phase face-centered cubic(fcc)high/medium-entropy alloys(H/MEAs)exhibit a much higher tendency to form nanoscale deformation twins than conventional fcc metals with similar low stacking fault energies(SFEs).This extraordinary propensity for nanotwin formation in H/MEAs cannot therefore be ex-plained by their low SFEs alone.Here,using in situ compression tests of CrCoNi in comparison with Ag nanopillars inside a transmission electron microscope,we found that in the CrCoNi MEA,a high density of nanoscale twins continuously formed with an average thickness of 4.6 nm.In contrast,for similar experiments on Ag with almost identical SFE,following the nucleation of a few twins,they could further thicken to above one hundred nanometers by twin boundary migration.Molecular dynamics calculations indicated that in the highly-concentrated CrCoNi solid solution,the magnitude of the energy barriers for nucleating a stacking fault as a twin precursor in the pristine lattice and for the thickening of an existing twin both span a wide range and largely overlap with each other.Therefore,twin thickening through successive addition of atomic layers is prone to discontinuation,giving way to the nucleation of new twins at other sites where a lower energy barrier is encountered for partial-dislocation mediated fault formation.
基金supported by the Guangdong Provincial Key Lab of Translational Medicine in Lung Cancer(2017B030314120)the Guangdong Provincial People’s Hospital Scientific Research Funds for Leading Medical Talents in Guangdong Province(KJ012019426)+2 种基金the National Natural Science Foundation of China(82072562 and 82202997)the China Postdoctoral Science Foundation(2021M701422)the High-Level Hospital Construction Project(DFJH201810).
文摘No direct comparison has been performed between different programmed cell death-1(PD-1)inhibitors for first-line treatment in patients with advanced non-small cell lung cancer(NSCLC).The feasibility of using PD-L1-expression-guided immunotherapy remains unknown.In this open-label,phase 2 study(NCT04252365),patients with advanced NSCLC without EGFR or ALK alterations were randomized(1:1)to receive sintilimab or pembrolizumab monotherapy(PD-L1 expression≥50%),or sintilimab or pembrolizumab plus platinum-based chemotherapy(PD-L1 expression<50%).The sample size was calculated by optimal two-stage design.The primary endpoint was the objective response rate(ORR).The study included 71 patients(sintilimab arms,n=35;pembrolizumab arms,n=36)and met its primary endpoint,with a confirmed ORR of 51.4%(18/35)in the sintilimab arms.The confirmed ORR(95%confidence interval)was 46.2%(19.2%,74.9%)and 42.9%(17.7%,71.1%)for patients treated with sintilimab and pembrolizumab monotherapy;and 54.5%(32.2%,75.6%)and 45.4%(24.4%,67.8%)for those treated with sintilimab-and pembrolizumab-based combination therapies.The median progression-free survival was6.9 versus 8.1 months for all sintilimab-treated versus all pembrolizumab-treated patients,respectively,in which it was 7.6 versus 11.0 months in monotherapy and 7.4 versus 7.1 months in combination therapies.The median overall survival was 14.9 versus 21.3 months for all sintilimab-treated versus all pembrolizumab-treated patients,respectively,in which it was 14.9 versus 22.6 months in monotherapy and 14.7 versus 17.3 months in combination therapies.Treatment-related adverse events were consistent with safety outcomes of monotherapy and combination therapy in previous phase III studies.However,the incidence of rash was higher with sintilimab than pembrolizumab monotherapy.This is the first prospective phase 2 study to directly compare two anti-PD-1 antibodies as first-line treatment in advanced NSCLC.Sintilimab was efficacious and well-tolerated irrespective of PD-L1 expression level in patients with advanced NSCLC and had similar efficacy and safety to pembrolizumab.
基金supported by the National Natural Science Foundation of China(51971167,52031011,12004294)the Ministry of Science and Technology(2017YFA0700703 for Gan B)the National Youth Talents Program(Ding J)。
