In this study,a comprehensive analysis of microstructural features,morphology,crystal structures,and interface structures of long-period stacking ordered(LPSO)structures in a non-equilibrium Mg_(97)Zn_(1)Y_(16)Ca_(0.4...In this study,a comprehensive analysis of microstructural features,morphology,crystal structures,and interface structures of long-period stacking ordered(LPSO)structures in a non-equilibrium Mg_(97)Zn_(1)Y_(16)Ca_(0.4)alloy cast in a steel mold was carried out.The addition of Ca element plays an important role in the refinement of LPSO structure.The result reveals new poly-types including 20H F2F2F4,60R(F2F3F3)_(3),and 66H F2F3F3F2(F6)_(4)featuring a 6-Mg structure,alongside the prevalent 18R and 14H LPSO structures.The incoherent interface between 20H and the Mg matrix is split into two dislocation arrays,leading to the formation of a segment of 60R_(1).Moreover,the superstructure 116L,designated as(F2)_(18)F4,is formed through the ordered distribution of F4 stacking faults in 18R.展开更多
Weak interactions prevent the magnetic particles from achieving excellent electromagnetic wave absorp-tion(EMA)at a low filler loading(FL).The construction of one-dimensional magnetic metal fibers(1D-MMFs)contributes ...Weak interactions prevent the magnetic particles from achieving excellent electromagnetic wave absorp-tion(EMA)at a low filler loading(FL).The construction of one-dimensional magnetic metal fibers(1D-MMFs)contributes to the formation of an electromagnetic(EM)coupling network,enhancing EM properties at a low FL.However,precisely controlling the length of 1D-MMFs to regulate permittivity at low FL poses a challenge.Herein,a novel magnetic field-assisted growth strategy was used to fabricate Co-based fibers with adjustable permittivity and aspect ratios.With a variety of FL changes,centimeter-level Co long fibers(Co-lf)consistently exhibited higher permittivity than Co particles and Co short fibers due to the enhancement of the effective EM coupling.The Co-lf exhibits excellent EMA performance(-54.85 dB,5.8 GHz)at 10 wt.%FL.Meanwhile,heterogeneous interfaces were introduced to increase the interfacial polarization through a fine phosphorylation design,resulting in elevated EMA performances(-51.50 dB,6.6 GHz)at 10 wt.%FL for Co_(2)P/Co long fibers.This study improves the orderliness of the particle arrangement by regulating the length of 1D-MMFs,which affects the behavior of electrons inside the fibers,providing a new perspective for improving the EMA properties of magnetic materials at a low FL.展开更多
Mimicking the electric microenvironment of natural tissue is a promising strategy for developing biomedical implants. However, current research has not taken biomimetic electrical functional units into consideration w...Mimicking the electric microenvironment of natural tissue is a promising strategy for developing biomedical implants. However, current research has not taken biomimetic electrical functional units into consideration when designing biomedical implants. In this research, ordered structures with Schottky heterojunction functional unit (OSSH) were constructed on titanium implant surfaces for bone regeneration regulation. The Schottky heterojunction functional unit is composed of periodically distributed titanium microdomain and titanium oxide microdomain with different carrier densities and surface potentials. The OSSH regulates the M2-type polarization of macrophages to a regenerative immune response by activating the PI3K-AKT-mTOR signal pathway and further promotes osteogenic differentiation of rat bone marrow mesenchymal stem cells. This work provides fundamental insights into the biological effects driven by the Schottky heterojunction functional units that can electrically modulate osteogenesis.展开更多
14H, 18R and 24R long-period stacking ordered （LPSO） structures were observed in the as-cast Mg-3Cu-1Mn-2Zn-1Y damping alloy using transmission electron microscopy （TEM）. These LPSO structures contained Mg, Y, Cu ...14H, 18R and 24R long-period stacking ordered （LPSO） structures were observed in the as-cast Mg-3Cu-1Mn-2Zn-1Y damping alloy using transmission electron microscopy （TEM）. These LPSO structures contained Mg, Y, Cu and Zn and thus they were quaternary phases. Sharp diffraction pattern of the 24R structure was obtained and the angle between and g10024R was measured to be 5.03°. During high resolution TEM observations, lattice fringes with two characteristic spacings were observed within the 24R structure. Based on the experimental results, 6H, 7H and three 8H are suggested as the building blocks of 18R, 14H and 24R structures, respectively. The 24R unit cell can be interpreted as the stacking of 8H building blocks in the same shear direction with a shear angle of about 5.03°. The imperfect 24R structures are in order or disorder arrangements of principal 8H and minor 6H blocks. This double-block structure model is also applicable to other reported defects in LPSO structures.展开更多
The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr(wt.%)alloy with fine plate-like 14H-LPSO structures aged at 240℃were investigated using transmission electron microscopy(TEM)and hig...The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr(wt.%)alloy with fine plate-like 14H-LPSO structures aged at 240℃were investigated using transmission electron microscopy(TEM)and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).Fine plate-like 14H-LPSO structures precipitate after heat treatment at 500℃for 2 h,andβ-type phases precipitate after the alloy is aged at 240℃.The long-period atomic stacking sequence of 14H-LPSO structures along the[0001]αdirection is ABABCACACACBABA.After being aged at 240℃for 2 h,theβ-type phases are the ordered solution clusters,zig-zag GP zones,and a small number ofβ′phases.The peak hardness is obtained at 240℃for 18 h with a Brinell hardness of 112,theβ-type phases areβ’phases and local RE-rich structures.After being aged at 240℃for 100 h,theβ-type phases areβ’,β1 andβ’F phases.β′phases nucleate from the zig-zag GP zones directly withoutβ″phases,and then transform intoβ1 phase byβ’→β’F→β1 transformations.The Zn not only can form LPSO structure,but also is the constituent element ofβ1 phases.LPSO structures have a certain hindrance to the coarsening ofβ’andβ1 along<0001>α.展开更多
The recent development of high-strength magnesium alloys is focused on the role of the strengthening phases with a novel long-period stacking-ordered (LPSO) structure. This review detailed the main factors influencing...The recent development of high-strength magnesium alloys is focused on the role of the strengthening phases with a novel long-period stacking-ordered (LPSO) structure. This review detailed the main factors influencing the formation of LPSO phases, including alloying ele-ments, preparation methods, and heat treatments. Furthermore, process control in structure types, formation and transformation behavior, strengthening and toughening mechanisms of the LPSO phase were discussed. Finally, the current problems and development trends of high-strength Mg-Zn-RE alloys were also put forward.展开更多
Mg-Zn-Y alloys with long-period stacking ordered structures were prepared by an ingot casting method. The corrosion performance of Mg-Zn-Y alloys was studied by combining gas-collecting test, immersion test and electr...Mg-Zn-Y alloys with long-period stacking ordered structures were prepared by an ingot casting method. The corrosion performance of Mg-Zn-Y alloys was studied by combining gas-collecting test, immersion test and electrochemical measurements in order to determine the corrosion rate and mechanism of the alloys. The results showed that the volume fraction of Mg（12）YZn phase increased and the shape of the Mg（12）YZn phase changed from discontinuous to continuous net-like with increasing Zn and Y content. The corrosion rate of the alloys greatly depended on the distribution and volume fraction of the Mg（12）YZn phase. Corrosion products appeared at the junction of Mg phase and Mg（12）YZn phase, indicating that the Mg（12）YZn phase accelerated galvanic corrosion of Mg matrix. Mg（97）Zn1Y2 alloy shows the lowest corrosion rate due to the continuous distribution of Mg（12）YZn phase.展开更多
Formation of β’ phase in long-period stacking ordered(LPSO) structures in an Mg;Co;Y;(at.%) alloy after aging at 200 °C for 24 h or electron beam(EB) irradiation has been studied by high-angle annular dark-fiel...Formation of β’ phase in long-period stacking ordered(LPSO) structures in an Mg;Co;Y;(at.%) alloy after aging at 200 °C for 24 h or electron beam(EB) irradiation has been studied by high-angle annular dark-field scanning transmission electron microscopy(HAADFSTEM). β’ phase was precipitated only in the Mg matrix but not in LPSO structures after aging at 200 °C for 24 h. LPSO structure containing stacking defects transforms into the β’-long phase during EB irradiation, which plays a key role in accelerating solute atoms’ diffusion. New complex β’(LPSO) structures formed in the alloy after EB irradiation, such as β’(12 H) structure with an orthorhombic lattice(Mg;Y, Cmcm,a = 2 _(a0)= 0.642 nm, b=4√3_(a0), c = 6 _(c0)= 3.12 nm).展开更多
Large-scale Fe-6.5 wt.%Si ingot with excellent formability is required for a pilot line producing sheets through hot/cold rolling.The variation of the as-cast microstructure,ordered structures and the formability of t...Large-scale Fe-6.5 wt.%Si ingot with excellent formability is required for a pilot line producing sheets through hot/cold rolling.The variation of the as-cast microstructure,ordered structures and the formability of the Fe-6.5 wt.%Si alloy ingots with the cooling rate during casting was investigated.Under air-cooling condition,inhomogeneous microstructures with a low proportion of equiaxed grains were formed,but the formation of ordered structures was partially inhibited,especially DO3.Homogeneous microstructures with a high proportion of equiaxed grains were observed under the condition of furnace cooling,but the ordered structures were fully generated,and the degree of order is high.It is generally believed that high degree of order is the main factor of brittleness,but the homogeneous microstructure(including grain morphology and size)of the furnace-cooled sample helps to improve the formability.The influence of these two aspects on formability is contradictory.Therefore,the formability is tested through the flow stress during the compression and the microstructure after the compression.The results show that the furnace-cooled sample has better formability.For large-scale ingots,the control of as-cast microstructure becomes more significant than the control of degree of order.Slow cooling during casting is important for the large-scale ingots to have good formability meeting the requirements of direct hot rolling.展开更多
Discovering publication hierarchically-ordered contexts is the main task in context-based searching paradigm. The proposed techniques to discover publication contexts relies on the availability of domain-specific inpu...Discovering publication hierarchically-ordered contexts is the main task in context-based searching paradigm. The proposed techniques to discover publication contexts relies on the availability of domain-specific inputs, namely a pre-specified ontology terms. A problem with this technique is that the needed domain-specific inputs may not be available in some scientific disciplines. In this paper, we propose utilizing a powerful input that is naturally available in any scientific discipline to discover the hierarchically-ordered contexts of it, namely paper citation and co-authorship graphs. More specifically, we propose a set of domain-specific bibliometry-aware features that are automatically computable instead of domain-specific inputs that need experts’ efforts to prepare. Another benefit behind considering bibliometric-features to adapt to the special characteristics of the literature environment being targeted, which in turn facilitates contexts membership decision making. One key advantage of our proposal is that it considers temporal changes of the targeted publication set.展开更多
Both solute-segregated long-period stacking ordered(LPSO)structure and stacking faults(SFs)are essential in strengthening rare-earth(RE)Mg alloys.Herein,LPSO-enriched Mg and SFs-enriched Mg are fabricated and comparab...Both solute-segregated long-period stacking ordered(LPSO)structure and stacking faults(SFs)are essential in strengthening rare-earth(RE)Mg alloys.Herein,LPSO-enriched Mg and SFs-enriched Mg are fabricated and comparably investigated for fatigue performances.During fatigue,the Mg nanolayers between LPSO lamellae or SFs act as the gliding channels of dislocations.However,SFs-enriched Mg exhibits outstanding fatigue strength due to solute strengthening within Mg nanolayers.Solute strengthening is assumed to contribute to the local accumulation of basal dislocations and the activation of non-basal dislocations.Dislocations are restricted locally and cannot glide long distances to specimen surfaces,which mitigates fatigue-induced extrusions and slip markings,ultimately leading to an increase in fatigue strength.These findings guide the development of RE-Mg alloys towards a synergy between high tensile and high fatigue performances.展开更多
Because the grinding temperature is high when grinding using conventional disordered grinding wheels,the grinding quality improvement is limited when using single abrasive ordered grinding wheels,and the wheel prepara...Because the grinding temperature is high when grinding using conventional disordered grinding wheels,the grinding quality improvement is limited when using single abrasive ordered grinding wheels,and the wheel preparation process is complex and costly when using microstructured grinding wheels,abrasive groups ordered grinding wheels are widely investigated.However,there is a paucity of systematic analyses and comprehensive reviews focused on abrasive groups ordered grinding wheels.Therefore,this paper defines abrasive groups ordered grinding wheels and classifies them,based on their unique characteristics,into groups such as abrasive blocks ordered grinding wheel,fine grain structured grinding wheel,abrasive clusters ordered grinding wheel,and abrasive fibers ordered grinding wheel.We provide an overview of the latest advances in wheel structures,preparation methods,and abrasive selection for various types of abrasive groups ordered grinding wheels.Furthermore,we conduct a comparative analysis of the existing types,significant advantages,and challenges associated with the four types of abrasive groups ordered grinding wheels.Looking ahead,given the potential of abrasive groups ordered grinding wheels in reducing grinding force and temperature,we recommend further exploration of their application in combination with special processing techniques.This could pave the way for the development of machining processes that are more environmentally friendly,energy-efficient,and precise.展开更多
A Mg-14.28Gd-2.44Zn-0.54Zr （mass fraction, %） alloy was prepared by conventional ingot metallurgy （I/M）. The microstructure differences in as-cast and solution-treated alloys were investigated. Sliding tribologica...A Mg-14.28Gd-2.44Zn-0.54Zr （mass fraction, %） alloy was prepared by conventional ingot metallurgy （I/M）. The microstructure differences in as-cast and solution-treated alloys were investigated. Sliding tribological behaviors of the as-cast and solution-treated alloys were investigated under oil lubricant condition by pin-on-disc configuration. The wear loss and friction coefficients were measured at a load of 40 N and sliding speeds of 30-300 mm/s with a sliding distance of 5000 m at room temperature. The results show that the as-cast alloy is mainly composed ofα-Mg solid solution, the lamellar 14H-type long period stacking ordered （LPSO） structure within matrix, andβ-[（Mg,Zn）3Gd] phase. However, most of theβ-phase transforms to X-phase with 14H-type LPSO structure after solution heat treatment at 773 K for 35 h （T4）. The solution-treated alloy presents low wear-resistance, because the hard β-phase is converted into thermally-stable, ductile and soft X-Mg12GdZn phase with LPSO structure in the alloy.展开更多
Three-dimensional（3D）ordered mesoporous MnO2 was prepared using KIT-6 mesoporous molecular sieves as a hard template.The material was used for catalytic oxidation of HCHO.The material has high surface areas and the ...Three-dimensional（3D）ordered mesoporous MnO2 was prepared using KIT-6 mesoporous molecular sieves as a hard template.The material was used for catalytic oxidation of HCHO.The material has high surface areas and the mesoporous characteristics of the template,with cubic symmetry（ia3d）.It consists of a β-MnO2 crystalline phase corresponding to pyrolusite,with a rutile structure.Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the 3D-MnO2 catalyst has a large number of exposed Mn4＋ ions on the（110）crystal plane surfaces,with a lattice spacing of 0.311 nm; this enhances oxidation of HCHO.Complete conversion of HCHO to CO2 and H2O was achieved at 130 °C on 3D-MnO2; the same conversions on α-MnO2 and β-MnO2 nanorods were obtained at 140 and 180 °C,respectively,under the same conditions.The specific mesoporous structure,high specific surface area,and large number of surface Mn4＋ ions are responsible for the catalytic activity of 3D-MnO2 in HCHO oxidation.展开更多
The microstructure of the 18R-type long period stacking ordered （LPSO） phase in Mg 97 Y 2 Zn 1 alloy was investigated by the first principles calculation. The arrangement rule of Zn and Y atoms in the LPSO structure...The microstructure of the 18R-type long period stacking ordered （LPSO） phase in Mg 97 Y 2 Zn 1 alloy was investigated by the first principles calculation. The arrangement rule of Zn and Y atoms in the LPSO structure is determined theoretically. The calculation results reveal that the additive atoms are firstly located in the fault layers at the two ends of the 18R-type LPSO structure, and then extend to fault layers in the interior, which is in good agreement with the experimental observations. This feature also implies the microstructural relationship between 18R and other LPSO structures. The cohesive energy and the formation heat indicate the dependence of the stability of 18R LPSO structure on contents of Y and Zn atoms. The calculated electronic structures reveal the underlying mechanism of microstructure and the stability of 18R LPSO structure.展开更多
综述了国内外几种制备Mg_(97)ZnY_2合金的工艺特点和研究现状,分析了该合金中几种不同长周期结构(Long period stacking ordered structure,简称LPSO)的形成机制及堆跺方式,提出了Mg_(97)ZnY_2合金当前研究的主要问题,并展望了Mg_(97)Zn...综述了国内外几种制备Mg_(97)ZnY_2合金的工艺特点和研究现状,分析了该合金中几种不同长周期结构(Long period stacking ordered structure,简称LPSO)的形成机制及堆跺方式,提出了Mg_(97)ZnY_2合金当前研究的主要问题,并展望了Mg_(97)ZnY_2合金应用于现实生产的前景。展开更多
The microstructure and mechanical properties of Mg94Zn2Y4 extruded alloy containing long-period stacking ordered structures were systematically investigated by SEM and TEM analyses. The results show that the 18R-LPSO ...The microstructure and mechanical properties of Mg94Zn2Y4 extruded alloy containing long-period stacking ordered structures were systematically investigated by SEM and TEM analyses. The results show that the 18R-LPSO structure and α-Mg phase are observed in cast Mg94Zn2Y4 alloy. After extrusion, the LPSO structures are delaminated and Mg-slices with width of 50-200 nm are generated. By ageing at 498 K for 36 h, the ageing peak is attained andβ′phase is precipitated. Due to this novel precipitation, the microhardness ofα-Mg matrix increases apparently from HV108.9 to HV129.7. While the microhardness for LPSO structure is stabilized at about HV145. TEM observations and SAED patterns indicate that the β′ phase has unique orientation relationships betweenα-Mg and LPSO structures, the direction in the close-packed planes ofβ′precipitates perpendicular to that ofα-Mg and LPSO structures. The ultimate tensile strength for the peak-aged alloy achieves 410.7 MPa and the significant strength originates from the coexistence ofβ′precipitates and 18R-LPSO structures.展开更多
基金supported by the open research fund of Songshan Lake Materials Laboratory(No.2022SLABFN08)Guangxi Science and Technology Base and Talents Special Project(Nos.Guike AD20297034 and AD21220053)+2 种基金the National Natural Science Foundation of China(No.51801214 and 52171021)the Research Start-up Funding from Guangxi University of Science and Technology(No.03200150)the Middle-aged and Young Teachers’Basic Ability Promotion Project of Guangxi(No.2022KY0329)。
文摘In this study,a comprehensive analysis of microstructural features,morphology,crystal structures,and interface structures of long-period stacking ordered(LPSO)structures in a non-equilibrium Mg_(97)Zn_(1)Y_(16)Ca_(0.4)alloy cast in a steel mold was carried out.The addition of Ca element plays an important role in the refinement of LPSO structure.The result reveals new poly-types including 20H F2F2F4,60R(F2F3F3)_(3),and 66H F2F3F3F2(F6)_(4)featuring a 6-Mg structure,alongside the prevalent 18R and 14H LPSO structures.The incoherent interface between 20H and the Mg matrix is split into two dislocation arrays,leading to the formation of a segment of 60R_(1).Moreover,the superstructure 116L,designated as(F2)_(18)F4,is formed through the ordered distribution of F4 stacking faults in 18R.
基金supported by the National Key Research and Development Program of China(No.2024YFE0100600)the National Natural Science Foundation of China(No.52373303)+1 种基金the Shanghai Municipal Science and Technology Major Project(No.2021SHZDZX0100)the Fundamental Research Funds for the Central Universities and the Interdisciplinary Joint Research and Development Project of Tongji University(No.2022-4-ZD-01).
文摘Weak interactions prevent the magnetic particles from achieving excellent electromagnetic wave absorp-tion(EMA)at a low filler loading(FL).The construction of one-dimensional magnetic metal fibers(1D-MMFs)contributes to the formation of an electromagnetic(EM)coupling network,enhancing EM properties at a low FL.However,precisely controlling the length of 1D-MMFs to regulate permittivity at low FL poses a challenge.Herein,a novel magnetic field-assisted growth strategy was used to fabricate Co-based fibers with adjustable permittivity and aspect ratios.With a variety of FL changes,centimeter-level Co long fibers(Co-lf)consistently exhibited higher permittivity than Co particles and Co short fibers due to the enhancement of the effective EM coupling.The Co-lf exhibits excellent EMA performance(-54.85 dB,5.8 GHz)at 10 wt.%FL.Meanwhile,heterogeneous interfaces were introduced to increase the interfacial polarization through a fine phosphorylation design,resulting in elevated EMA performances(-51.50 dB,6.6 GHz)at 10 wt.%FL for Co_(2)P/Co long fibers.This study improves the orderliness of the particle arrangement by regulating the length of 1D-MMFs,which affects the behavior of electrons inside the fibers,providing a new perspective for improving the EMA properties of magnetic materials at a low FL.
基金supported by the National Natural Science Foundation of China(Nos.52072127,52201297,U21A2055,and U22A20160)the China Postdoctoral Science Foundation(No.2022M711200)the Royal Society(No.IEC/NSFC/191344)(UK).
文摘Mimicking the electric microenvironment of natural tissue is a promising strategy for developing biomedical implants. However, current research has not taken biomimetic electrical functional units into consideration when designing biomedical implants. In this research, ordered structures with Schottky heterojunction functional unit (OSSH) were constructed on titanium implant surfaces for bone regeneration regulation. The Schottky heterojunction functional unit is composed of periodically distributed titanium microdomain and titanium oxide microdomain with different carrier densities and surface potentials. The OSSH regulates the M2-type polarization of macrophages to a regenerative immune response by activating the PI3K-AKT-mTOR signal pathway and further promotes osteogenic differentiation of rat bone marrow mesenchymal stem cells. This work provides fundamental insights into the biological effects driven by the Schottky heterojunction functional units that can electrically modulate osteogenesis.
基金Project (2009CB623704) supported by the National Basic Research Program of ChinaProject (50971076) supported by the National Natural Science Foundation of China
文摘14H, 18R and 24R long-period stacking ordered （LPSO） structures were observed in the as-cast Mg-3Cu-1Mn-2Zn-1Y damping alloy using transmission electron microscopy （TEM）. These LPSO structures contained Mg, Y, Cu and Zn and thus they were quaternary phases. Sharp diffraction pattern of the 24R structure was obtained and the angle between and g10024R was measured to be 5.03°. During high resolution TEM observations, lattice fringes with two characteristic spacings were observed within the 24R structure. Based on the experimental results, 6H, 7H and three 8H are suggested as the building blocks of 18R, 14H and 24R structures, respectively. The 24R unit cell can be interpreted as the stacking of 8H building blocks in the same shear direction with a shear angle of about 5.03°. The imperfect 24R structures are in order or disorder arrangements of principal 8H and minor 6H blocks. This double-block structure model is also applicable to other reported defects in LPSO structures.
基金Projects(51871195,51501015)supported by the National Natural Science Foundation of ChinaProject(TC170A5SU-1)supported by Ministry of Industry and Information Technology of China。
文摘The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr(wt.%)alloy with fine plate-like 14H-LPSO structures aged at 240℃were investigated using transmission electron microscopy(TEM)and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).Fine plate-like 14H-LPSO structures precipitate after heat treatment at 500℃for 2 h,andβ-type phases precipitate after the alloy is aged at 240℃.The long-period atomic stacking sequence of 14H-LPSO structures along the[0001]αdirection is ABABCACACACBABA.After being aged at 240℃for 2 h,theβ-type phases are the ordered solution clusters,zig-zag GP zones,and a small number ofβ′phases.The peak hardness is obtained at 240℃for 18 h with a Brinell hardness of 112,theβ-type phases areβ’phases and local RE-rich structures.After being aged at 240℃for 100 h,theβ-type phases areβ’,β1 andβ’F phases.β′phases nucleate from the zig-zag GP zones directly withoutβ″phases,and then transform intoβ1 phase byβ’→β’F→β1 transformations.The Zn not only can form LPSO structure,but also is the constituent element ofβ1 phases.LPSO structures have a certain hindrance to the coarsening ofβ’andβ1 along<0001>α.
基金supported by the Opening Project of Jiangsu Key Laboratory of Advanced Metallic Materials (No. AMM201007)the Natural Science Foundation of Jiangsu Province of China (No. BK2010521)
文摘The recent development of high-strength magnesium alloys is focused on the role of the strengthening phases with a novel long-period stacking-ordered (LPSO) structure. This review detailed the main factors influencing the formation of LPSO phases, including alloying ele-ments, preparation methods, and heat treatments. Furthermore, process control in structure types, formation and transformation behavior, strengthening and toughening mechanisms of the LPSO phase were discussed. Finally, the current problems and development trends of high-strength Mg-Zn-RE alloys were also put forward.
基金support of the National Natural Science Foundation of China (No.50571073)the Ph.D. Programs Foundation of Ministry of Education of China (No. 20111402110004)the Natural Science Foundation of Shanxi Province, China (No.2009011028-3)
文摘Mg-Zn-Y alloys with long-period stacking ordered structures were prepared by an ingot casting method. The corrosion performance of Mg-Zn-Y alloys was studied by combining gas-collecting test, immersion test and electrochemical measurements in order to determine the corrosion rate and mechanism of the alloys. The results showed that the volume fraction of Mg（12）YZn phase increased and the shape of the Mg（12）YZn phase changed from discontinuous to continuous net-like with increasing Zn and Y content. The corrosion rate of the alloys greatly depended on the distribution and volume fraction of the Mg（12）YZn phase. Corrosion products appeared at the junction of Mg phase and Mg（12）YZn phase, indicating that the Mg（12）YZn phase accelerated galvanic corrosion of Mg matrix. Mg（97）Zn1Y2 alloy shows the lowest corrosion rate due to the continuous distribution of Mg（12）YZn phase.
基金supported by the National Natural Science Foundation of China(Grant No.51801214 and 51871222)。
文摘Formation of β’ phase in long-period stacking ordered(LPSO) structures in an Mg;Co;Y;(at.%) alloy after aging at 200 °C for 24 h or electron beam(EB) irradiation has been studied by high-angle annular dark-field scanning transmission electron microscopy(HAADFSTEM). β’ phase was precipitated only in the Mg matrix but not in LPSO structures after aging at 200 °C for 24 h. LPSO structure containing stacking defects transforms into the β’-long phase during EB irradiation, which plays a key role in accelerating solute atoms’ diffusion. New complex β’(LPSO) structures formed in the alloy after EB irradiation, such as β’(12 H) structure with an orthorhombic lattice(Mg;Y, Cmcm,a = 2 _(a0)= 0.642 nm, b=4√3_(a0), c = 6 _(c0)= 3.12 nm).
基金National Natural Science Foundation of China(51471031,U1660115)the State Key Laboratory for Advanced Metals and Materials(2016Z-17)are gratefully acknowledged.
文摘Large-scale Fe-6.5 wt.%Si ingot with excellent formability is required for a pilot line producing sheets through hot/cold rolling.The variation of the as-cast microstructure,ordered structures and the formability of the Fe-6.5 wt.%Si alloy ingots with the cooling rate during casting was investigated.Under air-cooling condition,inhomogeneous microstructures with a low proportion of equiaxed grains were formed,but the formation of ordered structures was partially inhibited,especially DO3.Homogeneous microstructures with a high proportion of equiaxed grains were observed under the condition of furnace cooling,but the ordered structures were fully generated,and the degree of order is high.It is generally believed that high degree of order is the main factor of brittleness,but the homogeneous microstructure(including grain morphology and size)of the furnace-cooled sample helps to improve the formability.The influence of these two aspects on formability is contradictory.Therefore,the formability is tested through the flow stress during the compression and the microstructure after the compression.The results show that the furnace-cooled sample has better formability.For large-scale ingots,the control of as-cast microstructure becomes more significant than the control of degree of order.Slow cooling during casting is important for the large-scale ingots to have good formability meeting the requirements of direct hot rolling.
文摘Discovering publication hierarchically-ordered contexts is the main task in context-based searching paradigm. The proposed techniques to discover publication contexts relies on the availability of domain-specific inputs, namely a pre-specified ontology terms. A problem with this technique is that the needed domain-specific inputs may not be available in some scientific disciplines. In this paper, we propose utilizing a powerful input that is naturally available in any scientific discipline to discover the hierarchically-ordered contexts of it, namely paper citation and co-authorship graphs. More specifically, we propose a set of domain-specific bibliometry-aware features that are automatically computable instead of domain-specific inputs that need experts’ efforts to prepare. Another benefit behind considering bibliometric-features to adapt to the special characteristics of the literature environment being targeted, which in turn facilitates contexts membership decision making. One key advantage of our proposal is that it considers temporal changes of the targeted publication set.
基金supported by National Natural Science Foundation of China(Nos.12102280,12172238,12332012)Postdoctoral Fellowship Program of CPSF(No.GZB20230473)+1 种基金Support of Ultramicroscopy Research Center(URC,Kyushu University)are highly acknowledged.Yao Chen acknowledges the support of JSPS Fellowship(No.JP22F22720)JSPS KAKENHI(No JP22K03828).
文摘Both solute-segregated long-period stacking ordered(LPSO)structure and stacking faults(SFs)are essential in strengthening rare-earth(RE)Mg alloys.Herein,LPSO-enriched Mg and SFs-enriched Mg are fabricated and comparably investigated for fatigue performances.During fatigue,the Mg nanolayers between LPSO lamellae or SFs act as the gliding channels of dislocations.However,SFs-enriched Mg exhibits outstanding fatigue strength due to solute strengthening within Mg nanolayers.Solute strengthening is assumed to contribute to the local accumulation of basal dislocations and the activation of non-basal dislocations.Dislocations are restricted locally and cannot glide long distances to specimen surfaces,which mitigates fatigue-induced extrusions and slip markings,ultimately leading to an increase in fatigue strength.These findings guide the development of RE-Mg alloys towards a synergy between high tensile and high fatigue performances.
基金Supported by National Natural Science Foundation of China(Grant No.52175401)Hunan Provincial Postgraduate Scientific Research Innovation Project(Grant No.QL20230244)+1 种基金Enterprise Innovation and Development Joint Program of National Natural Science Foundation of China(Grant No.U20B2032)Hunan Provincial Science and Technology Innovation Program(Grant No.2022RC1050).
文摘Because the grinding temperature is high when grinding using conventional disordered grinding wheels,the grinding quality improvement is limited when using single abrasive ordered grinding wheels,and the wheel preparation process is complex and costly when using microstructured grinding wheels,abrasive groups ordered grinding wheels are widely investigated.However,there is a paucity of systematic analyses and comprehensive reviews focused on abrasive groups ordered grinding wheels.Therefore,this paper defines abrasive groups ordered grinding wheels and classifies them,based on their unique characteristics,into groups such as abrasive blocks ordered grinding wheel,fine grain structured grinding wheel,abrasive clusters ordered grinding wheel,and abrasive fibers ordered grinding wheel.We provide an overview of the latest advances in wheel structures,preparation methods,and abrasive selection for various types of abrasive groups ordered grinding wheels.Furthermore,we conduct a comparative analysis of the existing types,significant advantages,and challenges associated with the four types of abrasive groups ordered grinding wheels.Looking ahead,given the potential of abrasive groups ordered grinding wheels in reducing grinding force and temperature,we recommend further exploration of their application in combination with special processing techniques.This could pave the way for the development of machining processes that are more environmentally friendly,energy-efficient,and precise.
基金Projects(51304135,50971089)supported by the National Natural Science Foundation of ChinaProject(A1420110045)supported by National Defense Basic Research Plan,China+1 种基金Project(11QH1401200)supported by the Shanghai Phospherus Program,ChinaProject(NCET-11-0329)supported by the New Century Excellent Talents in University of Ministry of Education of China
文摘A Mg-14.28Gd-2.44Zn-0.54Zr （mass fraction, %） alloy was prepared by conventional ingot metallurgy （I/M）. The microstructure differences in as-cast and solution-treated alloys were investigated. Sliding tribological behaviors of the as-cast and solution-treated alloys were investigated under oil lubricant condition by pin-on-disc configuration. The wear loss and friction coefficients were measured at a load of 40 N and sliding speeds of 30-300 mm/s with a sliding distance of 5000 m at room temperature. The results show that the as-cast alloy is mainly composed ofα-Mg solid solution, the lamellar 14H-type long period stacking ordered （LPSO） structure within matrix, andβ-[（Mg,Zn）3Gd] phase. However, most of theβ-phase transforms to X-phase with 14H-type LPSO structure after solution heat treatment at 773 K for 35 h （T4）. The solution-treated alloy presents low wear-resistance, because the hard β-phase is converted into thermally-stable, ductile and soft X-Mg12GdZn phase with LPSO structure in the alloy.
基金supported by the National Natural Science Foundation of China(21325731,21221004 and 51478241)~~
文摘Three-dimensional（3D）ordered mesoporous MnO2 was prepared using KIT-6 mesoporous molecular sieves as a hard template.The material was used for catalytic oxidation of HCHO.The material has high surface areas and the mesoporous characteristics of the template,with cubic symmetry（ia3d）.It consists of a β-MnO2 crystalline phase corresponding to pyrolusite,with a rutile structure.Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the 3D-MnO2 catalyst has a large number of exposed Mn4＋ ions on the（110）crystal plane surfaces,with a lattice spacing of 0.311 nm; this enhances oxidation of HCHO.Complete conversion of HCHO to CO2 and H2O was achieved at 130 °C on 3D-MnO2; the same conversions on α-MnO2 and β-MnO2 nanorods were obtained at 140 and 180 °C,respectively,under the same conditions.The specific mesoporous structure,high specific surface area,and large number of surface Mn4＋ ions are responsible for the catalytic activity of 3D-MnO2 in HCHO oxidation.
基金Projects(50861002,51071053)supported by the National Natural Science Foundation of ChinaProject(0991051)supported by NaturalScience Foundation of Guangxi Province,China+1 种基金Project(KF0803)supported by Open Project of Key Laboratory of Materials Design and Preparation Technology of Hunan Province,ChinaProject(X071117)supported by Scientific Research Foundation of Guangxi University,China
文摘The microstructure of the 18R-type long period stacking ordered （LPSO） phase in Mg 97 Y 2 Zn 1 alloy was investigated by the first principles calculation. The arrangement rule of Zn and Y atoms in the LPSO structure is determined theoretically. The calculation results reveal that the additive atoms are firstly located in the fault layers at the two ends of the 18R-type LPSO structure, and then extend to fault layers in the interior, which is in good agreement with the experimental observations. This feature also implies the microstructural relationship between 18R and other LPSO structures. The cohesive energy and the formation heat indicate the dependence of the stability of 18R LPSO structure on contents of Y and Zn atoms. The calculated electronic structures reveal the underlying mechanism of microstructure and the stability of 18R LPSO structure.
文摘综述了国内外几种制备Mg_(97)ZnY_2合金的工艺特点和研究现状,分析了该合金中几种不同长周期结构(Long period stacking ordered structure,简称LPSO)的形成机制及堆跺方式,提出了Mg_(97)ZnY_2合金当前研究的主要问题,并展望了Mg_(97)ZnY_2合金应用于现实生产的前景。
基金Project (BK2010392) supported by the Natural Science Foundation of Jiangsu Province of ChinaProject (3212000502) supported by the Innovation Foundation of Southeast University,China
文摘The microstructure and mechanical properties of Mg94Zn2Y4 extruded alloy containing long-period stacking ordered structures were systematically investigated by SEM and TEM analyses. The results show that the 18R-LPSO structure and α-Mg phase are observed in cast Mg94Zn2Y4 alloy. After extrusion, the LPSO structures are delaminated and Mg-slices with width of 50-200 nm are generated. By ageing at 498 K for 36 h, the ageing peak is attained andβ′phase is precipitated. Due to this novel precipitation, the microhardness ofα-Mg matrix increases apparently from HV108.9 to HV129.7. While the microhardness for LPSO structure is stabilized at about HV145. TEM observations and SAED patterns indicate that the β′ phase has unique orientation relationships betweenα-Mg and LPSO structures, the direction in the close-packed planes ofβ′precipitates perpendicular to that ofα-Mg and LPSO structures. The ultimate tensile strength for the peak-aged alloy achieves 410.7 MPa and the significant strength originates from the coexistence ofβ′precipitates and 18R-LPSO structures.
