The relationship between activities of involved deformation mechanisms and the evolution of microstructure and texture during uniaxial tension of AZ31 magnesium alloy with a rare non-basal texture has been thoroughly ...The relationship between activities of involved deformation mechanisms and the evolution of microstructure and texture during uniaxial tension of AZ31 magnesium alloy with a rare non-basal texture has been thoroughly investigated in the present study by means of electron backscattered diffraction(EBSD) measurement and visco-plastic self-consistent(VPSC) modeling. These results show that except basal slip and prismatic slip, {10■2} extension twin(ET) also plays a significant role during plastic deformation. With the increasing tilted angle between loading direction and rolling direction(RD) of sheet, the activity of {10■2} ET possesses a decreasing tendency and its role in plastic deformation changes from the one mainly sustaining plastic strain to the one mainly accommodating local strain between individual grains. When {10■2} ET serves as a carrier of plastic strain, it mainly results in the formation of basal texture component(c-axis//ND, normal direction). By comparison, when the role of {10■2} ET is to accommodate local strain, it mainly brings about the formation of prismatic texture component(c-axis//TD, transverse direction). At large plastic deformation, the competition between basal slip and pyramidal<c+a> slip is responsible for the concentration of tilted basal poles towards ND within all deformed samples. The larger difference is between the activities of basal slip and pyramidal <c+a> slip, the smaller separation is between these two tilted basal poles. Besides,VPSC modeling overesttmates volume fractions of {10■2} ET in samples with angle of 0 to 30° between loading direction and RD of sheet because interactions between twin variants are not included in VPSC modeling procedure at the present form. In addition, as compatible deformation between individual grains cannot be considered in VPSC modeling, the predicted volume fractions of {10■2} ET in samples with angle of 45 to 90° between loading direction and RD of sheet are smaller than the correspondingly measured results.展开更多
In-plane uniaxial tension of AZ31 magnesium alloy sheet with non-basal texture has been conducted in order to demonstrate the effects of loading direction on the microstructure evolution and mechanical properties at a...In-plane uniaxial tension of AZ31 magnesium alloy sheet with non-basal texture has been conducted in order to demonstrate the effects of loading direction on the microstructure evolution and mechanical properties at ambient temperature.Loading axes are chosen to be along five directions distributed between rolling direction(RD)and transverse direction(TD),allowing various activities in involved slip and twinning modes to take place.As for twinning modes,electron backscattered diffraction observations confirm that the contribution of{1011}compression twinning is minimal to the plastic deformation of all deformed samples.By comparison,{1012}extension twinning(ET)not only serves as an important carrier on sustaining and accommodating plastic strain but also contributes to the emergence of TD-component texture with the progression of plastic strain.In terms of slip modes,analysis on Schmid factor demonstrates that the increasing tilted angle between loading direction and RD of sheet is unfavorable to the activation of basalslip,whereas it contributes to the activation of prismaticslip.These observations consequently explain the increasing tendency of 0.2%proof yield stress.Moreover,the activations of basalslip and{1012}ET collectively contribute to the concentration of two tilted basal poles toward normal direction.With increasing angle between loading direction and RD,the activations of basalslip and{1012}ET are gradually weakened.This leads to a weakening tendency about concentration of two tilted basal poles,a generally increasing tendency about Lankford value(r-value)and a generally decreasing tendency about strain-hardening exponent(n-value).展开更多
Two novel types of irrational orientation relationships(ORs)betweenβ-Mg_(2)Sn precipitates and theα-Mg matrix were observed in a Mg-4 Sn alloy aged at 160℃.In contrast to that for the dominantβ-Mg_(2)Sn laths lyin...Two novel types of irrational orientation relationships(ORs)betweenβ-Mg_(2)Sn precipitates and theα-Mg matrix were observed in a Mg-4 Sn alloy aged at 160℃.In contrast to that for the dominantβ-Mg_(2)Sn laths lying on the(0001)_αbasal plane of the matrix,the precipitates with the irrational ORs are inclined or normal to(0001)_α.Specifically,the precipitates that adopt the OR of[011]_(β)//[2110]_α,with(111)_(β)deviating approximately 4.7°from(0002)_α,have a long axis parallel to[0001]_α.The precipitates with the OR of[011]_(β)//[2110]_α,with(111)_(β)deviating approximately 13.50 from(0002)_α,exhibit a long axis of[0211]_α.Both types of precipitates have a habit plane(HP)of(2110)_α.The interface orientations of the precipitates associated with the irrational ORs are interpreted by a good matching sites(GMS)method.A thorough examination of the crystallographic features of theβ-Mg_(2)Sn precipitates in the literature shows that the precipitates with most rational ORs have a HP parallel to(0001)_α,and those with most irrational ORs have a HP(or long axis)inclined or normal to(0001)_α.The preferences of the precipitates with different irrational ORs have also been analyzed by examining the lattice matching condition across the interfaces between the precipitates and the matrix.展开更多
Objective:Triple-negative breast cancer(estrogen receptor-negative,progesterone receptor-negative and Her2-negative) can be classified into two subtypes:basal and non-basal phenotype.And the basal phenotype is associa...Objective:Triple-negative breast cancer(estrogen receptor-negative,progesterone receptor-negative and Her2-negative) can be classified into two subtypes:basal and non-basal phenotype.And the basal phenotype is associated with poor outcome.The purpose of this study was to figure out the differences of clinicopathological characters and related factors of prognosis between these two subtypes.Methods:Immunohistochemical staining was performed for the CK5/6,CK17 basal markers and EGFR on biopsy samples from 40 triple-negative patients and the clinicopathology features of these samples were investigated.Results:Seventy percent of the patients were diagnosed as the basal phenotype.Compared with the non-basal phenotype,the basal phenotype lesions were significantly larger in diameter with a high nuclear grade.In the node-negative group the basal phenotype clearly showed the same clinicopathological differences.There was statistically significant concordance among all three antibodies.Conclusion:Expression of basal markers identifies a biologically and clinically distinct subgroup of TN tumors,justifying the use of basal markers to define the basal or the non-basal phenotype.It is important to help the doctor deciding the therapeutic strategy for patient with triple-negative breast cancer.展开更多
Cryogenic rolling experiments have been conducted on the AZ31 magnesium(Mg)alloy sheet with bimodal non-basal texture,which is fabricated via the newly developed equal channel angular rolling and continuous bending pr...Cryogenic rolling experiments have been conducted on the AZ31 magnesium(Mg)alloy sheet with bimodal non-basal texture,which is fabricated via the newly developed equal channel angular rolling and continuous bending process with subsequent annealing(ECAR-CB-A)process.Results demonstrate that this sheet shows no edge cracks until the accumulated thickness reduction reaches about 18.5%,which is about 105.6%larger than that of the sheet with traditional basal texture.Characterization experiments including optical microstructure(OM),X-ray diffractometer(XRD),and electron backscatter diffraction(EBSD)measurements are then performed to explore the microstructure characteristics,texture evolution and deformation mechanisms during cryogenic rolling.Experimental observations confirm the occurrence of abundant{10–12}extension twins(ETs),twin-twin interactions among{10–12}ET variants and{10–12}-{10–12}double twins(DTs).The twinning behaviors as for{10–12}ETs are responsible for the concentration of c-axes of grains towards normal direction(ND)and the formation of transverse direction(TD)-component texture at the beginning of cryogenic rolling.The twinning behaviors with respect to{10–12}-{10–12}DTs are responsible for the disappearance of TD-component texture at the later stage of cryogenic rolling.The involved deformation mechanisms can be summarized as follows:Firstly{10–12}ETs dominate the plastic deformation.Subsequently,dislocation slip,especially basal<a>slip,starts to sustain more plastic strain,while{10–12}ETs occur more frequently and enlarge continuously,resulting in the formation of twin-twin interaction among{10–12}ET variants.With the increasing rolling passes,{10–12}-{10–12}DTs incorporate in the plastic deformation and dislocation slip serves as the major one to sustain plastic strain.The activities of basal<a>slip,{10–12}ETs and{10–12}-{10–12}DTs benefit in accommodating the plastic strain in sheet thickness,which contributes to the improved rolling formability in AZ31 Mg alloy sheet with bimodal non-basal texture during cryogenic rolling.展开更多
Here we firstly report a series of new deep eutectic solvents(DESs) induced by small amounts of crown ether complex and mainly formed by polyethylene glycol. These DESs not only presented the ultra-deep extraction of ...Here we firstly report a series of new deep eutectic solvents(DESs) induced by small amounts of crown ether complex and mainly formed by polyethylene glycol. These DESs not only presented the ultra-deep extraction of non-basic N-compounds from fuel oils, but also opened up the possibility of other new applications in chemistry and materials science.展开更多
Since mid-2016,the low pathogenic H7N9 influenza virus has evolved into a highly pathogenic(HP)phenotype in China,raising many concerns about public health and poultry industry.The insertion of a“KRTA”motif at hemag...Since mid-2016,the low pathogenic H7N9 influenza virus has evolved into a highly pathogenic(HP)phenotype in China,raising many concerns about public health and poultry industry.The insertion of a“KRTA”motif at hemagglutinin cleavage site(HACS)occurred in the early stage of HP H7N9 variants.During the co-circulation,the HACS of HP-H7N9 variants were more polymorphic in birds and humans.Although HP-H7N9 variants,unlike the H5 subtype virus,exhibited the insertions of basic and non-basic amino acids,the underlying function of those insertions and substitutions remains unclear.The results of bioinformatics analysis indicated that the PEVPKRKRTAR/G motif of HACS had become the dominant motif in China.Then,we generated six H7N9 viruses bearing the PEIPKGR/G,PEVPKGR/G,PEVPKRKRTAR/G,PEVPKGKRTAR/G,PEVPKGKRIAR/G,and PEVPKRKRR/G motifs.Interestingly,after the deletion of threonine and alanine(TA)at HACS,the H7N9 viruses manifested decreased thermostability and virulence in mice,and the PEVPKRKRTAR/G-motif virus is prevalent in birds and humans probably due to its increased transmissibility and moderate virulence.By contrast,the insertion of non-basic amino acid isoleucine and alanine(IA)decreased the transmissibility in chickens and virulence in mice.Remarkably,the I335V substitution of H7N9 virus enhanced infectivity and transmission in chickens,suggesting that the combination of mutations and insertions of amino acids at the HACS promoted replication and pathogenicity in chickens and mice.The ongoing evolution of H7N9 increasingly threatens public health and poultry industry,so,its comprehensive surveillance and prevention of H7N9 viruses should be pursued.展开更多
Different application scenarios put forward diverse requirements of mechanical properties for magnesium alloys.In this study,the extruded Mg-Sc-Nd-Zn alloy series with high plasticity and medium strength was developed...Different application scenarios put forward diverse requirements of mechanical properties for magnesium alloys.In this study,the extruded Mg-Sc-Nd-Zn alloy series with high plasticity and medium strength was developed.The uniformly distributed Mg_(3)Nd(β_(1))phase,high-density twins,and the activated non-basal dislocation slips contribute to the high plasticity of Mg-Sc-Nd alloy.With the addition of Zn element,the appearance of coarse ScZn phases,which prevents the activation of{1012}tensile twins,leads to an increase in strength but a simultaneous decrease in the plasticity of the extruded alloys.Adjusting the Zn content in the Mg-Sc-Nd-xZn allows a series of alloys with various strengths and plasticity matching.The results obtained in this work are of great importance for developing a regulatable magnesium alloy series that aims at different application scenarios.展开更多
Age hardening is often used to optimize the mechanical properties of as-deformed Mg-based materials in industry,whereas the improvement of strength is usually accompanied by the significant loss of ductility,which hin...Age hardening is often used to optimize the mechanical properties of as-deformed Mg-based materials in industry,whereas the improvement of strength is usually accompanied by the significant loss of ductility,which hinders the application of Mg-based materials in structural components.In the present work,high strength-ductility synergy(the yield strength of 263±9 MPa,ultimate tensile strength of 398±7 MPa and elongation to fracture of 34%±1%)was realized in as-extruded AlN/AZ91 composites after optimiz-ing aging processes.Microstructural characterization shows that AlN particles induced a large number of geometrically necessary dislocations around the AlN/Mg interface during extrusion,which decreased the nucleation barrier and provided more heterogeneous nucleation sites forγ-Mg 17 Al 12 continuous precipi-tation.Meanwhile,95%of residual dislocations in as-extruded AlN/AZ91 composites were annihilated dur-ing peak-aging,suppressing the growth and coarsening of continuous precipitates.Therefore,high density of nano-sizedγ-Mg 17 Al 12 continuous precipitates was produced in as-extruded AlN/AZ91 composites af-ter peak-aging.During tension,gliding dislocations bypassed sphericalγ-Mg 17 Al 12 nano-precipitates by Orowan looping rather than cutting mechanism,which induced a strong block on dislocation motion.So high yield strength was mainly attributed to the high density of non-shearableγ-Mg 17 Al 12 nano-precipitates with spherical morphology,which was different from other Mg-Al-based systems.The results of texture evolution and slip trace analysis demonstrated that the suppression of extension twinning and less basal slip was due to the enhanced activity of pyramidalc+aslip in as-extruded AlN/AZ91 com-posites after peak-aging during the room temperature tension,meanwhile,the dislocation density of as-extruded AlN/AZ91 composites was significantly decreased during peak-aging,then higher elongation to fracture was achieved.展开更多
The rolling direction（RD） and the transverse direction（TD） samples were obtained from an as-rolled ZK60 magnesium alloy sheet with strong anisotropy of initial texture and their mechanical properties were tested a...The rolling direction（RD） and the transverse direction（TD） samples were obtained from an as-rolled ZK60 magnesium alloy sheet with strong anisotropy of initial texture and their mechanical properties were tested at various deformation temperatures. Meanwhile, the microstructure and texture of these samples after fracture were investigated. Results revealed that a higher flow stress along the RD than that along the TD at room temperature were ascribed to the strong anisotropy of transitional texture, and this texture effect was remarkably weakened with the increase of deformation temperature. Deformation structure was dominant at 100℃, and was replaced by dynamic recrystallization structure when the deformation temperature increased to 200℃ and 300℃. The texture presented a strong texture（transitional texture in the RD sample and basal texture in the TD sample） at 100℃, but its intensity visibly decreased and texture components became more disperse at 200℃ and 300℃. These microstructure and texture results were employed in conjunction with calculated results to argue that raising deformation temperature could increase the activity of non-basal slip by tailoring the relative critical resolved shear stress of each deformation mode and finally result in low texture effect on mechanical anisotropy.展开更多
Due to the insufficient slip systems,Mg and its alloys exhibit poor ductility during plastic deformation at room temperature.To solve this problem,alloying is considered as a most effective method to improve the ducti...Due to the insufficient slip systems,Mg and its alloys exhibit poor ductility during plastic deformation at room temperature.To solve this problem,alloying is considered as a most effective method to improve the ductility of Mg alloys,which attracts wide attentions of industries.However,it is still a challenge to understand the ductilization mechanism,because of the complicated alloying elements and their interactions with Mg matrix.In this work,pure Mg and Mg-Y alloys were comparatively studied to investigate the effect of Y addition on microstructure evolution and mechanical properties.A huge increase of uniform elongation,from 5.3%to 20.7%,was achieved via only 3 wt%addition of yttrium.TEM results revealed that the only activated slip system in pure Mg was basalslip,led to its poor ductility at room temperature.In contrast,a large number of stacking faults and non-basal dislocations with<c>component were observed in the deformed Mg-Y alloy,which was proposed as the main reason for significant improvement of strain hardening and ductility.High resolution TEM indicated that most of the stacking faults were II and 12 intrinsic faults,which played a critical role in improving the ductility of Mg-Y alloy.Addition of Y into Mg alloy decreased the stacking fault energy,which induced high density stacking faults in the grain interior.展开更多
基金the National Natural Science Foundation of China(Grant Nos.51805064,51701034,51822509)the Scientific and Technological Research Program of Chongqing Municipal Education Commission(Grant Nos.KJQN201801137)the Basic and Advanced Research Project of CQ CSTC(Grant Nos.cstc2017jcyj AX0062,cstc2018jcyj AX0035)。
文摘The relationship between activities of involved deformation mechanisms and the evolution of microstructure and texture during uniaxial tension of AZ31 magnesium alloy with a rare non-basal texture has been thoroughly investigated in the present study by means of electron backscattered diffraction(EBSD) measurement and visco-plastic self-consistent(VPSC) modeling. These results show that except basal slip and prismatic slip, {10■2} extension twin(ET) also plays a significant role during plastic deformation. With the increasing tilted angle between loading direction and rolling direction(RD) of sheet, the activity of {10■2} ET possesses a decreasing tendency and its role in plastic deformation changes from the one mainly sustaining plastic strain to the one mainly accommodating local strain between individual grains. When {10■2} ET serves as a carrier of plastic strain, it mainly results in the formation of basal texture component(c-axis//ND, normal direction). By comparison, when the role of {10■2} ET is to accommodate local strain, it mainly brings about the formation of prismatic texture component(c-axis//TD, transverse direction). At large plastic deformation, the competition between basal slip and pyramidal<c+a> slip is responsible for the concentration of tilted basal poles towards ND within all deformed samples. The larger difference is between the activities of basal slip and pyramidal <c+a> slip, the smaller separation is between these two tilted basal poles. Besides,VPSC modeling overesttmates volume fractions of {10■2} ET in samples with angle of 0 to 30° between loading direction and RD of sheet because interactions between twin variants are not included in VPSC modeling procedure at the present form. In addition, as compatible deformation between individual grains cannot be considered in VPSC modeling, the predicted volume fractions of {10■2} ET in samples with angle of 45 to 90° between loading direction and RD of sheet are smaller than the correspondingly measured results.
基金supported by the National Natural Science Foundation of China(Grant Nos.51805064,51822509,51701034)the Scientifi c and Technological Research Program of Chongqing Municipal Education Commission(Grant No.KJQN201801137)+1 种基金the Basic and Advanced Research Project of Chongqing Science and Technology Commission(Grant Nos.cstc2017jcyjAX0062,cstc2018jcyjAX0035)the Chongqing University Key Laboratory of Micro/Nano Materials Engineering and Technology(Grant No.KFJJ2003)。
文摘In-plane uniaxial tension of AZ31 magnesium alloy sheet with non-basal texture has been conducted in order to demonstrate the effects of loading direction on the microstructure evolution and mechanical properties at ambient temperature.Loading axes are chosen to be along five directions distributed between rolling direction(RD)and transverse direction(TD),allowing various activities in involved slip and twinning modes to take place.As for twinning modes,electron backscattered diffraction observations confirm that the contribution of{1011}compression twinning is minimal to the plastic deformation of all deformed samples.By comparison,{1012}extension twinning(ET)not only serves as an important carrier on sustaining and accommodating plastic strain but also contributes to the emergence of TD-component texture with the progression of plastic strain.In terms of slip modes,analysis on Schmid factor demonstrates that the increasing tilted angle between loading direction and RD of sheet is unfavorable to the activation of basalslip,whereas it contributes to the activation of prismaticslip.These observations consequently explain the increasing tendency of 0.2%proof yield stress.Moreover,the activations of basalslip and{1012}ET collectively contribute to the concentration of two tilted basal poles toward normal direction.With increasing angle between loading direction and RD,the activations of basalslip and{1012}ET are gradually weakened.This leads to a weakening tendency about concentration of two tilted basal poles,a generally increasing tendency about Lankford value(r-value)and a generally decreasing tendency about strain-hardening exponent(n-value).
基金the Major Science and Technology Project of Sichuan Province(Grant No.2020ZDZX0011)the Fundamental Research Funds for the Central Universities。
文摘Two novel types of irrational orientation relationships(ORs)betweenβ-Mg_(2)Sn precipitates and theα-Mg matrix were observed in a Mg-4 Sn alloy aged at 160℃.In contrast to that for the dominantβ-Mg_(2)Sn laths lying on the(0001)_αbasal plane of the matrix,the precipitates with the irrational ORs are inclined or normal to(0001)_α.Specifically,the precipitates that adopt the OR of[011]_(β)//[2110]_α,with(111)_(β)deviating approximately 4.7°from(0002)_α,have a long axis parallel to[0001]_α.The precipitates with the OR of[011]_(β)//[2110]_α,with(111)_(β)deviating approximately 13.50 from(0002)_α,exhibit a long axis of[0211]_α.Both types of precipitates have a habit plane(HP)of(2110)_α.The interface orientations of the precipitates associated with the irrational ORs are interpreted by a good matching sites(GMS)method.A thorough examination of the crystallographic features of theβ-Mg_(2)Sn precipitates in the literature shows that the precipitates with most rational ORs have a HP parallel to(0001)_α,and those with most irrational ORs have a HP(or long axis)inclined or normal to(0001)_α.The preferences of the precipitates with different irrational ORs have also been analyzed by examining the lattice matching condition across the interfaces between the precipitates and the matrix.
基金Supported by a grant from the National Natural Science Foundation of Hubei Province (No.2009CDB063)
文摘Objective:Triple-negative breast cancer(estrogen receptor-negative,progesterone receptor-negative and Her2-negative) can be classified into two subtypes:basal and non-basal phenotype.And the basal phenotype is associated with poor outcome.The purpose of this study was to figure out the differences of clinicopathological characters and related factors of prognosis between these two subtypes.Methods:Immunohistochemical staining was performed for the CK5/6,CK17 basal markers and EGFR on biopsy samples from 40 triple-negative patients and the clinicopathology features of these samples were investigated.Results:Seventy percent of the patients were diagnosed as the basal phenotype.Compared with the non-basal phenotype,the basal phenotype lesions were significantly larger in diameter with a high nuclear grade.In the node-negative group the basal phenotype clearly showed the same clinicopathological differences.There was statistically significant concordance among all three antibodies.Conclusion:Expression of basal markers identifies a biologically and clinically distinct subgroup of TN tumors,justifying the use of basal markers to define the basal or the non-basal phenotype.It is important to help the doctor deciding the therapeutic strategy for patient with triple-negative breast cancer.
基金supported by the National Natural Science Foundation of China(Grant Nos.51805064,51822509)the Qingnian project of science and technology research program of Chongqing Education Commission of China(Grant No.KJQN202101141).
文摘Cryogenic rolling experiments have been conducted on the AZ31 magnesium(Mg)alloy sheet with bimodal non-basal texture,which is fabricated via the newly developed equal channel angular rolling and continuous bending process with subsequent annealing(ECAR-CB-A)process.Results demonstrate that this sheet shows no edge cracks until the accumulated thickness reduction reaches about 18.5%,which is about 105.6%larger than that of the sheet with traditional basal texture.Characterization experiments including optical microstructure(OM),X-ray diffractometer(XRD),and electron backscatter diffraction(EBSD)measurements are then performed to explore the microstructure characteristics,texture evolution and deformation mechanisms during cryogenic rolling.Experimental observations confirm the occurrence of abundant{10–12}extension twins(ETs),twin-twin interactions among{10–12}ET variants and{10–12}-{10–12}double twins(DTs).The twinning behaviors as for{10–12}ETs are responsible for the concentration of c-axes of grains towards normal direction(ND)and the formation of transverse direction(TD)-component texture at the beginning of cryogenic rolling.The twinning behaviors with respect to{10–12}-{10–12}DTs are responsible for the disappearance of TD-component texture at the later stage of cryogenic rolling.The involved deformation mechanisms can be summarized as follows:Firstly{10–12}ETs dominate the plastic deformation.Subsequently,dislocation slip,especially basal<a>slip,starts to sustain more plastic strain,while{10–12}ETs occur more frequently and enlarge continuously,resulting in the formation of twin-twin interaction among{10–12}ET variants.With the increasing rolling passes,{10–12}-{10–12}DTs incorporate in the plastic deformation and dislocation slip serves as the major one to sustain plastic strain.The activities of basal<a>slip,{10–12}ETs and{10–12}-{10–12}DTs benefit in accommodating the plastic strain in sheet thickness,which contributes to the improved rolling formability in AZ31 Mg alloy sheet with bimodal non-basal texture during cryogenic rolling.
基金supported by the National Natrual Sciece Foundation of China (Nos. 21650110454, 21675164, 2 822407)the CAS-President International Fellowship Initiative (No. 2017PC0014)the Funds for Distinguished Young Scientists of Gansu (No. 1506RJDA281)
文摘Here we firstly report a series of new deep eutectic solvents(DESs) induced by small amounts of crown ether complex and mainly formed by polyethylene glycol. These DESs not only presented the ultra-deep extraction of non-basic N-compounds from fuel oils, but also opened up the possibility of other new applications in chemistry and materials science.
基金supported by National Natural Science Foundation of China(31672586 and 31830097)the Key Research and Development Program of Guangdong Province(2019B020218004)+2 种基金Earmarked Found for China Agriculture Research System(CARS-41-G16)Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme(2018,Wenbao Qi)Young Scholars of Yangtze River Scholar Professor Program(2019,Wenbao Qi)
文摘Since mid-2016,the low pathogenic H7N9 influenza virus has evolved into a highly pathogenic(HP)phenotype in China,raising many concerns about public health and poultry industry.The insertion of a“KRTA”motif at hemagglutinin cleavage site(HACS)occurred in the early stage of HP H7N9 variants.During the co-circulation,the HACS of HP-H7N9 variants were more polymorphic in birds and humans.Although HP-H7N9 variants,unlike the H5 subtype virus,exhibited the insertions of basic and non-basic amino acids,the underlying function of those insertions and substitutions remains unclear.The results of bioinformatics analysis indicated that the PEVPKRKRTAR/G motif of HACS had become the dominant motif in China.Then,we generated six H7N9 viruses bearing the PEIPKGR/G,PEVPKGR/G,PEVPKRKRTAR/G,PEVPKGKRTAR/G,PEVPKGKRIAR/G,and PEVPKRKRR/G motifs.Interestingly,after the deletion of threonine and alanine(TA)at HACS,the H7N9 viruses manifested decreased thermostability and virulence in mice,and the PEVPKRKRTAR/G-motif virus is prevalent in birds and humans probably due to its increased transmissibility and moderate virulence.By contrast,the insertion of non-basic amino acid isoleucine and alanine(IA)decreased the transmissibility in chickens and virulence in mice.Remarkably,the I335V substitution of H7N9 virus enhanced infectivity and transmission in chickens,suggesting that the combination of mutations and insertions of amino acids at the HACS promoted replication and pathogenicity in chickens and mice.The ongoing evolution of H7N9 increasingly threatens public health and poultry industry,so,its comprehensive surveillance and prevention of H7N9 viruses should be pursued.
基金Project supported by the National Natural Science Foundation of China(52301107)the National Key Research and Development Program of China(2021YFC2400703)。
文摘Different application scenarios put forward diverse requirements of mechanical properties for magnesium alloys.In this study,the extruded Mg-Sc-Nd-Zn alloy series with high plasticity and medium strength was developed.The uniformly distributed Mg_(3)Nd(β_(1))phase,high-density twins,and the activated non-basal dislocation slips contribute to the high plasticity of Mg-Sc-Nd alloy.With the addition of Zn element,the appearance of coarse ScZn phases,which prevents the activation of{1012}tensile twins,leads to an increase in strength but a simultaneous decrease in the plasticity of the extruded alloys.Adjusting the Zn content in the Mg-Sc-Nd-xZn allows a series of alloys with various strengths and plasticity matching.The results obtained in this work are of great importance for developing a regulatable magnesium alloy series that aims at different application scenarios.
基金supported by the National Natural Science Foundation of China(Nos.52071268 and 51771151)the Key R&D Project of Shaanxi Province(No.2022GY-366)the Re-search Fund of the State Key Laboratory of Solidification Processing(NPU),China(No.2022-BJ-04).
文摘Age hardening is often used to optimize the mechanical properties of as-deformed Mg-based materials in industry,whereas the improvement of strength is usually accompanied by the significant loss of ductility,which hinders the application of Mg-based materials in structural components.In the present work,high strength-ductility synergy(the yield strength of 263±9 MPa,ultimate tensile strength of 398±7 MPa and elongation to fracture of 34%±1%)was realized in as-extruded AlN/AZ91 composites after optimiz-ing aging processes.Microstructural characterization shows that AlN particles induced a large number of geometrically necessary dislocations around the AlN/Mg interface during extrusion,which decreased the nucleation barrier and provided more heterogeneous nucleation sites forγ-Mg 17 Al 12 continuous precipi-tation.Meanwhile,95%of residual dislocations in as-extruded AlN/AZ91 composites were annihilated dur-ing peak-aging,suppressing the growth and coarsening of continuous precipitates.Therefore,high density of nano-sizedγ-Mg 17 Al 12 continuous precipitates was produced in as-extruded AlN/AZ91 composites af-ter peak-aging.During tension,gliding dislocations bypassed sphericalγ-Mg 17 Al 12 nano-precipitates by Orowan looping rather than cutting mechanism,which induced a strong block on dislocation motion.So high yield strength was mainly attributed to the high density of non-shearableγ-Mg 17 Al 12 nano-precipitates with spherical morphology,which was different from other Mg-Al-based systems.The results of texture evolution and slip trace analysis demonstrated that the suppression of extension twinning and less basal slip was due to the enhanced activity of pyramidalc+aslip in as-extruded AlN/AZ91 com-posites after peak-aging during the room temperature tension,meanwhile,the dislocation density of as-extruded AlN/AZ91 composites was significantly decreased during peak-aging,then higher elongation to fracture was achieved.
基金the National Natural Science Foundation of China(Nos.51704209,U1810208,U1810122)the Central Government Guided Local Science and Technology Development Projects,China(No.YDZJSX2021A010)+5 种基金the Projects of International Cooperation in Shanxi Province,China(Nos.201803D421086,201903D421076)Shanxi Province Patent Promotion Implementation Fund,China(No.20200718)the Technological Innovation Programs of Higher Education Institutions in Shanxi Province,China(No.201802034)Shanxi Province Scientific Facilities and Instruments Shared Service Platform of Magnesium-based Materials Electric Impulse Aided Forming,China(No.201805D141005)Science and Technology Major Project of Shanxi Province,China(Nos.20191102008,20191102007,20181101008)Yantai High-end Talent Introduction“Double Hundred Plan”,China(2021)。
基金supported by the Fund for Distinguished Young Scholars of China Academy of Space Technology(No.2021399)the National Natural Science Foundation of China(No.51805064)the Science and Technology Research Program of Chongqing Municipal Education Commission,China(No.KJQN202101141)。
基金supported financially by the National Natural Science Foundation of China (No. 51401064)the Sci-tech Development Project in Shandong Province (No. 2014GGX10211)+1 种基金the Sci-tech Major Project in Shandong Province (No. 2015ZDJQ02002)the Fundamental Research Funds for the Central Universities (No. HIT.NSRIF.2016109)
文摘The rolling direction（RD） and the transverse direction（TD） samples were obtained from an as-rolled ZK60 magnesium alloy sheet with strong anisotropy of initial texture and their mechanical properties were tested at various deformation temperatures. Meanwhile, the microstructure and texture of these samples after fracture were investigated. Results revealed that a higher flow stress along the RD than that along the TD at room temperature were ascribed to the strong anisotropy of transitional texture, and this texture effect was remarkably weakened with the increase of deformation temperature. Deformation structure was dominant at 100℃, and was replaced by dynamic recrystallization structure when the deformation temperature increased to 200℃ and 300℃. The texture presented a strong texture（transitional texture in the RD sample and basal texture in the TD sample） at 100℃, but its intensity visibly decreased and texture components became more disperse at 200℃ and 300℃. These microstructure and texture results were employed in conjunction with calculated results to argue that raising deformation temperature could increase the activity of non-basal slip by tailoring the relative critical resolved shear stress of each deformation mode and finally result in low texture effect on mechanical anisotropy.
基金the National Key R&D Program of China(2017YFA0204403)National Natural Science Foundation of China(51601003,51901103)the Fundamental Research Funds for the Central Universities(30918011342).
文摘Due to the insufficient slip systems,Mg and its alloys exhibit poor ductility during plastic deformation at room temperature.To solve this problem,alloying is considered as a most effective method to improve the ductility of Mg alloys,which attracts wide attentions of industries.However,it is still a challenge to understand the ductilization mechanism,because of the complicated alloying elements and their interactions with Mg matrix.In this work,pure Mg and Mg-Y alloys were comparatively studied to investigate the effect of Y addition on microstructure evolution and mechanical properties.A huge increase of uniform elongation,from 5.3%to 20.7%,was achieved via only 3 wt%addition of yttrium.TEM results revealed that the only activated slip system in pure Mg was basalslip,led to its poor ductility at room temperature.In contrast,a large number of stacking faults and non-basal dislocations with<c>component were observed in the deformed Mg-Y alloy,which was proposed as the main reason for significant improvement of strain hardening and ductility.High resolution TEM indicated that most of the stacking faults were II and 12 intrinsic faults,which played a critical role in improving the ductility of Mg-Y alloy.Addition of Y into Mg alloy decreased the stacking fault energy,which induced high density stacking faults in the grain interior.
