Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stre...Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stress within the surfacing welding layer. The results show that cracking in the surfacing welding layer is directly related to the producing of eutectic phase β' (NiAl) in the interdendritic region and high thermal stress within the surfacing welding layer. When the process of electric arc surfacing welding is changed from along straight line to along' Z' pattern, cracking in the surfacing welding layer of Ni3Al based alloy is prevented due to being reduced of both the cooling rate of liquid in the molten pool and the moving speed of the heat source. Reducing the melting volume of the substrate material by lowering the output power of electric arc welding would make the content of iron atoms in the molten pool decrease. and this also can reduce the trend of the eutectic reaction in the interdendfitic region and is helpful to Suppress cracking in the surfacing welding layer.展开更多
A kind of Subwavelength Planar Metallic Lenses (SPMLs) is proposed to realize far-field optical focusing in the visible range based on concentric rings with modulated width in a silver film. The width of each metallic...A kind of Subwavelength Planar Metallic Lenses (SPMLs) is proposed to realize far-field optical focusing in the visible range based on concentric rings with modulated width in a silver film. The width of each metallic ring is mutative so that the radiation fields of surface plasmon polaritons can be controlled and the relevant phase retardations can be modulated to make a beam focus at the desired position. For comparison, the Subwavelength Planar Dielectric Lenses (SPDLs) structured on silica glass with the same concentric ring shapes as SPMLs are analyzed, although without opaque metal coating on SPDLs, the computational results show that SPMLs can support higher intensity focal spot, narrower full-width half-maximum beam width, and longer depth of focus at the focal region under certain lens thickness due to the coupling of surface plasomon polaritons, diffracted evanescent waves and propagated electromagnetic waves.展开更多
The solidification methods of electromagnetic stirring(EMS)and non-electromagnetic stirring were employed to prepare Mg–6Gd–3Y–xZn–0.6Zr(x=1,1.5,2,3)alloys.The evolution of alloy microstructures and the changes in...The solidification methods of electromagnetic stirring(EMS)and non-electromagnetic stirring were employed to prepare Mg–6Gd–3Y–xZn–0.6Zr(x=1,1.5,2,3)alloys.The evolution of alloy microstructures and the changes in properties were analyzed for different Zn contents.It has been observed that in alloys without electromagnetic stirring,as the Zn content increases,the alloy structure gradually refines.The primary second phase transitions from Mg5RE phase to long-period stacking ordered(LPSO)phase,resulting in improved hardness and elongation.In alloys subjected to electromagnetic stirring,there is a relatively higher content of the second phase,primarily consisting of LPSO phase.After applying electromagnetic stirring,the quantity and the type of LPSO phase in the alloy change.The alloy structure becomes more uniform with electromagnetic stirring,resulting in increased hardness and reduced hardness gradients within the grains.The mechanical properties of alloys with electromagnetic stirring are superior to those without electromagnetic stirring.展开更多
The nature heritages are the precious legacy of nature with outstanding scientific and aesthetic value. They are quite different from other common ecotourism areas, because of its original and unique system, sensitive...The nature heritages are the precious legacy of nature with outstanding scientific and aesthetic value. They are quite different from other common ecotourism areas, because of its original and unique system, sensitive and vulnerable landscape, and peripheral cultural features. Therefore, the tourism development in the nature heritage sites should be on the premise of ecological security. The evaluation index system of tourism ecological security in nature heritage sites was constructed in this article by AHP and Delphi methods, including nature ecological security, landscape visual security and local culture ecological security, and the security thresholds of indices were also established. In the indices' weights of the evaluation model, the nature ecological security ranked the highest, followed by tourist landscape visual security and culture ecological security, which reflected the influence degree of the limited factor to tourism ecological security. Then, this paper carried out an empirical study of Kanas of Xinjiang Uygur Autonomous Region, China, which has the potential to be the World Nature Heritage. On the basis of the data attained from survey and observation on the spot, as well as questionnaire answered by tourists and local communities, the ecological security status in Kanas was evaluated. The result showed that the status of Kanas tourism ecological security was better, but there had some limiting factors. Lastly, effective measures were put forward to ensure its ecological security.展开更多
Most world natural heritage sites are designated partly by reason of their prominent aesthetic values in accordance with Article Ⅶ of World Natural Heritage Convention.In this paper, the aesthetic values of Kanas Nat...Most world natural heritage sites are designated partly by reason of their prominent aesthetic values in accordance with Article Ⅶ of World Natural Heritage Convention.In this paper, the aesthetic values of Kanas National Nature Reserve, which has potential for such designation, was analyzed quantitatively using scenic beauty estimation(SBE).The landscapes of 19 representative scenic spots in the Kanas National Nature Reserve in summer and autumn were selected as the objects of evaluation.The contributions of different landscape factors to the aesthetic value of the Kanas National Nature Reserve were revealed using a multivariate quantitative model.The main factors affecting the aesthetic value were waterscapes, vegetation, mountains, folk culture and the tourist environment.The t-test and F-test results are extremely significant.According to the results, some suggestions were given for conserving the landscapes in the Kanas National Nature Reserve.展开更多
The effects of conform continuous extrusion and subsequent heat treatment on the mechanical and wear-resistance properties of high-alloying Al–13Si–7.5Cu–1Mg alloy were investigated.The microstructures of alloys be...The effects of conform continuous extrusion and subsequent heat treatment on the mechanical and wear-resistance properties of high-alloying Al–13Si–7.5Cu–1Mg alloy were investigated.The microstructures of alloys before and after conform processing and aging were compared by transmission electron microscopy and scanning electron microscopy,respectively.The results reveal that the primary phases were broken and refined by intense shear deformation during conform processing.After the conform-prepared Al–13Si–7.5Cu–1Mg alloy was subjected to solid-solution treatment at 494℃for 1.5 h and aging at 180℃for 4 h,its hardness improved from HBS 115.8 to HBS 152.5 and its ultimate tensile strength increased from 112.6 to 486.8 MPa.Its wear resistance was also enhanced.The factors leading to the enhanced strength,hardness,and wear resistance of the alloy were discussed in detail.展开更多
Background Augmen ted reality(AR)smartglasses are considered as the next generation of smart devices to replace mobile phones,and are widely concerned.But at present,AR smartglasses are usually designed according to t...Background Augmen ted reality(AR)smartglasses are considered as the next generation of smart devices to replace mobile phones,and are widely concerned.But at present,AR smartglasses are usually designed according to the human normal eyes.In order to experience AR smartglasses perfectly,abnormal eye users must first wear diopters.Methods For people with astigmatism to use AR smartglasses without wearing a diopter lens,a cylindrical lens waveguide grating is designed in this study based on the principle of holographic waveguide grating.First,a cylindrical lens waveguide substrate is constructed for external light deflection to satisfy the users'normal viewing of the real world.Further,a variable period grating structure is established based on the cylindrical lens waveguide substrate to normally emit the light from the virtual world in the optical machine to the human eyes.Finally,the structural parameters of grating are optimized to improve the diffraction efficiency.Results The results show that the structure of cylindrical lens waveguide grating allows people with astigmatism to wear AR smartglasses directly.The total light utilization rate reaches 90%with excellent imaging uniformity.The brightness difference is less than 0.92%and the vertical field of view is 10°.Conclusions This research serves as a guide for AR product designs for people with long/short sightedness and promotes the development of such products.展开更多
Vitamin A (VA) plays an essential role in modulating both the gut microbiota and gut barrier function.Short-chain fatty acids (SCFAs),as metabolites of the gut microbiota,protect the physiological intestinal barrier;h...Vitamin A (VA) plays an essential role in modulating both the gut microbiota and gut barrier function.Short-chain fatty acids (SCFAs),as metabolites of the gut microbiota,protect the physiological intestinal barrier;however,they are compromised when VA is deficient.Thus,there is an urgent need to understand how and which SCFAs modulate colonic epithelial barrier integrity in VA deficiency (VAD).Herein,compared with normal VA rats (VAN),at the beginning of pregnancy,we confirmed that the colonic desmosome junction was impaired in the VAD group,and the amounts of acetate,propionate,and butyrate declined because of the decreased abundance of SCFA-producing bacteria (Romboutsia ,Collinsella ,and Allobaculum ).The differentially expressed genes correlated with the gut barrier and the histone deacetylase complex between the VAD and VAN groups were enriched by RNA sequencing.In the VAD group,the expression levels of colonic CEA cell adhesion molecule 1 (CEACAM1) were down-regulated,and the levels of histone deacetylase 1 (HDAC1) and HDAC3 were up-regulated.Intriguingly,the above changes in the VAD groups were rescued by VA supplementation in the early postnatal period.Further study indicated that in Caco-2 cells,butyrate treatment significantly repressed the enrichment of HDAC3 on the promoter of the CEACAM1 gene to induce its expression.Our findings support that butyrate intervention can alleviate the impairment of colonic barrier function caused by VAD,and timely postnatal VA intervention may reverse the damage caused by VAD on gut barrier integrity during pregnancy.展开更多
The hot deformation characteristics of Rene88DT superalloy with directionally solidified micro- structure produced by electroslag remelting continuous directionally solidification (ESR-CDS) were studied in the tempe...The hot deformation characteristics of Rene88DT superalloy with directionally solidified micro- structure produced by electroslag remelting continuous directionally solidification (ESR-CDS) were studied in the temperature range of 1,040-1,140 ℃ and strain rate range of 0.001-1.000 s-1 by hot compression tests. Flow curves for Rene88DT alloy with initial directionally solidified (DS) microstructure exhibit pronounced peak stresses at the early stage of deformation followed by the occurrence of dynamic softening phenomenon. Rene88DT alloy with DS micro- structure shows higher flow peak stresses compared with HIPed P/M superalloy FGH4096, but the disparities in peak stresses between ESR-CDSed Rene88DT and HIPed P/M superalloy FGH4096 reduce as temperature increases. The improvement of hot workability of DS alloy with columnar grains avoiding the maximum shear stress comes true. A hot deformation constitutive equation as a function of strain that describes the dependence of flow stress on strain rate and temperature is established. Hot deformation apparent acti- vation energy (Q) varies not only with the strain rate and temperature but also with strain. The strain rate sensitivity exponent (m) map is established at the strain of 0.8, which reveals that global dynamic recrystallization (DRX) shows a relatively high m value in a large strain compression. Optimum parameters are predicted in two regions: T = 1,100-1,130 ℃, ε = 0.100-1.000 s-1 and T = 1,080- 1,100 ℃, ε = 0.010-100 s-1, which is based on pro- cessing maps and deformation microstructure observations.展开更多
Filter cake is critical to maintaining the stability of the excavation face of an underwater shield tunnel in a high-permeability stratum.In a high-permeability formation,generating an effective filter cake on the exc...Filter cake is critical to maintaining the stability of the excavation face of an underwater shield tunnel in a high-permeability stratum.In a high-permeability formation,generating an effective filter cake on the excavation face is difficult with a pure bentonite slurry,which penetrates the ground and may not achieve the required suspension pressure.Determining how to efficiently and quickly form a thin and low-permeability filter cake on the tunnel working face has become a key engineering problem in the construction of slurry shield tunnels in high-permeability strata.In this study,the relationship between slurry viscosity and the slurry pressure gradient of pure bentonite was established by performing slurry permeability experiments.The influence of slurry viscosity on the formation of the filter cake in a high-permeability formation was studied under different pressure gradients.In addition,the effect of additive particle size on the slurry filter cake formation was analyzed by introducing additives with different particle sizes to pure bentonite slurries with different viscosities.The test results indicate that(1)for the pure bentonite slurry,the critical initial pressure gradient can be used as a rough indicator of the formation of the filter cake,and the relationship between the critical maximum pore diameter and the average pore diameter of the for-mation can be compared to establish and analyze the formation law of the slurry filter cake;(2)adding particles to the slurry can enhance the effect of the pure bentonite slurry;and(3)adding coarse-grained materials can effectively improve the film-forming effect.The slurry is more compact when the particle size is close to the average pore size of the formation.展开更多
The Mg-1Gd-0.75Er-0.5Zn-0.18Zr(at.%)alloy with long-period stacking ordered(LPSO)phase was prepared by metal mold casting and hot extrusion.The extruded samples had a typical bimodal microstructure.The different fract...The Mg-1Gd-0.75Er-0.5Zn-0.18Zr(at.%)alloy with long-period stacking ordered(LPSO)phase was prepared by metal mold casting and hot extrusion.The extruded samples had a typical bimodal microstructure.The different fractions of equiaxed grains were observed in annealed samples.The percentage of fine grains decreased in the extruded Mg alloys with and without annealing treatment when the extrusion temperature was increased.The LPSO phases promote recrystal-lization behavior in the samples through particle-stimulated nucleation(PSN)mechanism.The Mg alloys extruded at 300℃ with or without annealing treatment obtained the best tensile properties.At the low extrusion temperature,more finely equiaxed grains with random texture are formed through PSN,and more LPSO phase kink bands are formed,which could improve the mechanical properties of the extruded Mg alloys.展开更多
文摘Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stress within the surfacing welding layer. The results show that cracking in the surfacing welding layer is directly related to the producing of eutectic phase β' (NiAl) in the interdendritic region and high thermal stress within the surfacing welding layer. When the process of electric arc surfacing welding is changed from along straight line to along' Z' pattern, cracking in the surfacing welding layer of Ni3Al based alloy is prevented due to being reduced of both the cooling rate of liquid in the molten pool and the moving speed of the heat source. Reducing the melting volume of the substrate material by lowering the output power of electric arc welding would make the content of iron atoms in the molten pool decrease. and this also can reduce the trend of the eutectic reaction in the interdendfitic region and is helpful to Suppress cracking in the surfacing welding layer.
文摘A kind of Subwavelength Planar Metallic Lenses (SPMLs) is proposed to realize far-field optical focusing in the visible range based on concentric rings with modulated width in a silver film. The width of each metallic ring is mutative so that the radiation fields of surface plasmon polaritons can be controlled and the relevant phase retardations can be modulated to make a beam focus at the desired position. For comparison, the Subwavelength Planar Dielectric Lenses (SPDLs) structured on silica glass with the same concentric ring shapes as SPMLs are analyzed, although without opaque metal coating on SPDLs, the computational results show that SPMLs can support higher intensity focal spot, narrower full-width half-maximum beam width, and longer depth of focus at the focal region under certain lens thickness due to the coupling of surface plasomon polaritons, diffracted evanescent waves and propagated electromagnetic waves.
基金supported by Postgraduate Research&Practice Innovation Program of Jiangsu Province(Project No.KYCX22_3792)Basic Science(Natural Science)Research General Project of Jiangsu Province Universities,China(22KJB430003).
文摘The solidification methods of electromagnetic stirring(EMS)and non-electromagnetic stirring were employed to prepare Mg–6Gd–3Y–xZn–0.6Zr(x=1,1.5,2,3)alloys.The evolution of alloy microstructures and the changes in properties were analyzed for different Zn contents.It has been observed that in alloys without electromagnetic stirring,as the Zn content increases,the alloy structure gradually refines.The primary second phase transitions from Mg5RE phase to long-period stacking ordered(LPSO)phase,resulting in improved hardness and elongation.In alloys subjected to electromagnetic stirring,there is a relatively higher content of the second phase,primarily consisting of LPSO phase.After applying electromagnetic stirring,the quantity and the type of LPSO phase in the alloy change.The alloy structure becomes more uniform with electromagnetic stirring,resulting in increased hardness and reduced hardness gradients within the grains.The mechanical properties of alloys with electromagnetic stirring are superior to those without electromagnetic stirring.
基金Under the auspices of National Natural Science Foundation of China (No. 40671057)Knowledge Innovation Pro-grams of Chinese Academy of Sciences (No. KZCX3-SW-355)
文摘The nature heritages are the precious legacy of nature with outstanding scientific and aesthetic value. They are quite different from other common ecotourism areas, because of its original and unique system, sensitive and vulnerable landscape, and peripheral cultural features. Therefore, the tourism development in the nature heritage sites should be on the premise of ecological security. The evaluation index system of tourism ecological security in nature heritage sites was constructed in this article by AHP and Delphi methods, including nature ecological security, landscape visual security and local culture ecological security, and the security thresholds of indices were also established. In the indices' weights of the evaluation model, the nature ecological security ranked the highest, followed by tourist landscape visual security and culture ecological security, which reflected the influence degree of the limited factor to tourism ecological security. Then, this paper carried out an empirical study of Kanas of Xinjiang Uygur Autonomous Region, China, which has the potential to be the World Nature Heritage. On the basis of the data attained from survey and observation on the spot, as well as questionnaire answered by tourists and local communities, the ecological security status in Kanas was evaluated. The result showed that the status of Kanas tourism ecological security was better, but there had some limiting factors. Lastly, effective measures were put forward to ensure its ecological security.
基金Under the auspices of National Natural Science Foundation of China (No. 40671057)Project of Science and Technology Plan of Xinjiang Uygur Autonomous Region (No. 200933128)
文摘Most world natural heritage sites are designated partly by reason of their prominent aesthetic values in accordance with Article Ⅶ of World Natural Heritage Convention.In this paper, the aesthetic values of Kanas National Nature Reserve, which has potential for such designation, was analyzed quantitatively using scenic beauty estimation(SBE).The landscapes of 19 representative scenic spots in the Kanas National Nature Reserve in summer and autumn were selected as the objects of evaluation.The contributions of different landscape factors to the aesthetic value of the Kanas National Nature Reserve were revealed using a multivariate quantitative model.The main factors affecting the aesthetic value were waterscapes, vegetation, mountains, folk culture and the tourist environment.The t-test and F-test results are extremely significant.According to the results, some suggestions were given for conserving the landscapes in the Kanas National Nature Reserve.
基金financially supported by the National Natural Science Foundation of China (No.51274245)
文摘The effects of conform continuous extrusion and subsequent heat treatment on the mechanical and wear-resistance properties of high-alloying Al–13Si–7.5Cu–1Mg alloy were investigated.The microstructures of alloys before and after conform processing and aging were compared by transmission electron microscopy and scanning electron microscopy,respectively.The results reveal that the primary phases were broken and refined by intense shear deformation during conform processing.After the conform-prepared Al–13Si–7.5Cu–1Mg alloy was subjected to solid-solution treatment at 494℃for 1.5 h and aging at 180℃for 4 h,its hardness improved from HBS 115.8 to HBS 152.5 and its ultimate tensile strength increased from 112.6 to 486.8 MPa.Its wear resistance was also enhanced.The factors leading to the enhanced strength,hardness,and wear resistance of the alloy were discussed in detail.
文摘Background Augmen ted reality(AR)smartglasses are considered as the next generation of smart devices to replace mobile phones,and are widely concerned.But at present,AR smartglasses are usually designed according to the human normal eyes.In order to experience AR smartglasses perfectly,abnormal eye users must first wear diopters.Methods For people with astigmatism to use AR smartglasses without wearing a diopter lens,a cylindrical lens waveguide grating is designed in this study based on the principle of holographic waveguide grating.First,a cylindrical lens waveguide substrate is constructed for external light deflection to satisfy the users'normal viewing of the real world.Further,a variable period grating structure is established based on the cylindrical lens waveguide substrate to normally emit the light from the virtual world in the optical machine to the human eyes.Finally,the structural parameters of grating are optimized to improve the diffraction efficiency.Results The results show that the structure of cylindrical lens waveguide grating allows people with astigmatism to wear AR smartglasses directly.The total light utilization rate reaches 90%with excellent imaging uniformity.The brightness difference is less than 0.92%and the vertical field of view is 10°.Conclusions This research serves as a guide for AR product designs for people with long/short sightedness and promotes the development of such products.
基金supported by grants from The National Natural Science Foundation of China(No.31971089)the General Project of Chongqing Natural Science Foundation(China)(No.CSTB2022NSCQ-MSX0107)the Scientific Research Innovation Project for Postgraduates in Chongqing City(China)(No.CYS19198).
文摘Vitamin A (VA) plays an essential role in modulating both the gut microbiota and gut barrier function.Short-chain fatty acids (SCFAs),as metabolites of the gut microbiota,protect the physiological intestinal barrier;however,they are compromised when VA is deficient.Thus,there is an urgent need to understand how and which SCFAs modulate colonic epithelial barrier integrity in VA deficiency (VAD).Herein,compared with normal VA rats (VAN),at the beginning of pregnancy,we confirmed that the colonic desmosome junction was impaired in the VAD group,and the amounts of acetate,propionate,and butyrate declined because of the decreased abundance of SCFA-producing bacteria (Romboutsia ,Collinsella ,and Allobaculum ).The differentially expressed genes correlated with the gut barrier and the histone deacetylase complex between the VAD and VAN groups were enriched by RNA sequencing.In the VAD group,the expression levels of colonic CEA cell adhesion molecule 1 (CEACAM1) were down-regulated,and the levels of histone deacetylase 1 (HDAC1) and HDAC3 were up-regulated.Intriguingly,the above changes in the VAD groups were rescued by VA supplementation in the early postnatal period.Further study indicated that in Caco-2 cells,butyrate treatment significantly repressed the enrichment of HDAC3 on the promoter of the CEACAM1 gene to induce its expression.Our findings support that butyrate intervention can alleviate the impairment of colonic barrier function caused by VAD,and timely postnatal VA intervention may reverse the damage caused by VAD on gut barrier integrity during pregnancy.
基金financially supported by the Military Supporting Project (No. JPPT125GJGG11)
文摘The hot deformation characteristics of Rene88DT superalloy with directionally solidified micro- structure produced by electroslag remelting continuous directionally solidification (ESR-CDS) were studied in the temperature range of 1,040-1,140 ℃ and strain rate range of 0.001-1.000 s-1 by hot compression tests. Flow curves for Rene88DT alloy with initial directionally solidified (DS) microstructure exhibit pronounced peak stresses at the early stage of deformation followed by the occurrence of dynamic softening phenomenon. Rene88DT alloy with DS micro- structure shows higher flow peak stresses compared with HIPed P/M superalloy FGH4096, but the disparities in peak stresses between ESR-CDSed Rene88DT and HIPed P/M superalloy FGH4096 reduce as temperature increases. The improvement of hot workability of DS alloy with columnar grains avoiding the maximum shear stress comes true. A hot deformation constitutive equation as a function of strain that describes the dependence of flow stress on strain rate and temperature is established. Hot deformation apparent acti- vation energy (Q) varies not only with the strain rate and temperature but also with strain. The strain rate sensitivity exponent (m) map is established at the strain of 0.8, which reveals that global dynamic recrystallization (DRX) shows a relatively high m value in a large strain compression. Optimum parameters are predicted in two regions: T = 1,100-1,130 ℃, ε = 0.100-1.000 s-1 and T = 1,080- 1,100 ℃, ε = 0.010-100 s-1, which is based on pro- cessing maps and deformation microstructure observations.
基金jointly supported by the Fundamental Research Funds for the Central Universities(Grant No.B200203089)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX20_0444)the financial support of National Natural Science Foundation of China(Grant Nos.U1765204 and 41772340).
文摘Filter cake is critical to maintaining the stability of the excavation face of an underwater shield tunnel in a high-permeability stratum.In a high-permeability formation,generating an effective filter cake on the excavation face is difficult with a pure bentonite slurry,which penetrates the ground and may not achieve the required suspension pressure.Determining how to efficiently and quickly form a thin and low-permeability filter cake on the tunnel working face has become a key engineering problem in the construction of slurry shield tunnels in high-permeability strata.In this study,the relationship between slurry viscosity and the slurry pressure gradient of pure bentonite was established by performing slurry permeability experiments.The influence of slurry viscosity on the formation of the filter cake in a high-permeability formation was studied under different pressure gradients.In addition,the effect of additive particle size on the slurry filter cake formation was analyzed by introducing additives with different particle sizes to pure bentonite slurries with different viscosities.The test results indicate that(1)for the pure bentonite slurry,the critical initial pressure gradient can be used as a rough indicator of the formation of the filter cake,and the relationship between the critical maximum pore diameter and the average pore diameter of the for-mation can be compared to establish and analyze the formation law of the slurry filter cake;(2)adding particles to the slurry can enhance the effect of the pure bentonite slurry;and(3)adding coarse-grained materials can effectively improve the film-forming effect.The slurry is more compact when the particle size is close to the average pore size of the formation.
基金support from Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX21_1764)Department Education of Jiangsu Province(No.22KJB430003)Guangdong Basic and Applied Basic Research Foundation(No.2020A1515110394).
文摘The Mg-1Gd-0.75Er-0.5Zn-0.18Zr(at.%)alloy with long-period stacking ordered(LPSO)phase was prepared by metal mold casting and hot extrusion.The extruded samples had a typical bimodal microstructure.The different fractions of equiaxed grains were observed in annealed samples.The percentage of fine grains decreased in the extruded Mg alloys with and without annealing treatment when the extrusion temperature was increased.The LPSO phases promote recrystal-lization behavior in the samples through particle-stimulated nucleation(PSN)mechanism.The Mg alloys extruded at 300℃ with or without annealing treatment obtained the best tensile properties.At the low extrusion temperature,more finely equiaxed grains with random texture are formed through PSN,and more LPSO phase kink bands are formed,which could improve the mechanical properties of the extruded Mg alloys.