Heat-resistant aluminum alloys are widely used in aerospace and automotive fields for manufacturing hot components due to their advantages in lightweight design and energy conservation.However,the high-temperature str...Heat-resistant aluminum alloys are widely used in aerospace and automotive fields for manufacturing hot components due to their advantages in lightweight design and energy conservation.However,the high-temperature strength of existing cast aluminum alloys is always limited to about 100 MPa at 350℃due to coarsening and transformation of strengthening phases.Here,we reveal that the yield strength and ultimate tensile strength of the T6 state Al-8.4Cu-2.3Ce-1.0Mn-0.5Ni-0.2Zr alloy at 400◦C increase by 34%and 44%after re-aging at 300℃for 100 h,and its thermal strength exhibits distinguished ad-vantage over traditional heat-resistant aluminum alloys.The enhanced elevated-temperature strength is attributed to the reprecipitation of the Ni-bearing T-Al_(20)Cu_(2)Mn_(3)phase,whose number density increases over one time.The significant segregation of Ni,Ce,and Zr elements at the interfaces helps improve the thermal stability of the T phase.The thermostable T phase effectively strengthens the matrix by in-hibiting dislocation motion.Meanwhile,a highly interconnected 3D intermetallic network along the grain boundaries can still remain after long-term re-aging at 300℃,which is conducive to imposing a drag on the grain boundaries at high temperatures.This finding offers a viable route for enhancing the elevated-temperature strength of heat-resistant aluminum alloys,which could provide expanded opportunities for higher-temperature applications.展开更多
This study investigates the impact of Zn alloying on the dispersion of the reinforcing particle in Mg_(2)Sn/Mg composites.In the composite,Zn manifests in three distinct forms:Zn segregation layer between Mg–Mg_(2)Sn...This study investigates the impact of Zn alloying on the dispersion of the reinforcing particle in Mg_(2)Sn/Mg composites.In the composite,Zn manifests in three distinct forms:Zn segregation layer between Mg–Mg_(2)Sn,the solid solution and the MgZn_(2)phase.First-principles calculations confirm that the formation of Zn segregation layer decreases the interfacial energy of the Mg–Mg_(2)Sn.Importantly,this segregation layer significantly enhances the comigration capability of Mg_(2)Sn particles with Mg matrix during sintering flow,effectively hindering the agglomeration and coarsening of the nano-sized reinforcing phase.The dense and uniformly distributed nano-sized Mg_(2)Sn significantly increases the activity of non-basal slip,ensuring good elongation of the composite while enhancing strength.It can be concluded that enhancing the comigration-ability of reinforcing particles with the matrix is an effective strategy for achieving controlled dispersion of high-volume reinforcing particles and an excellent combination of strength and ductility in magnesium matrix composites.展开更多
Dopamine polymerization reaction and hydrothermal method were used to prepare nickel coated Al_(2)O_(3)reinforcement phase(Ni/Al_(2)O_(3)).Ni/Al_(2)O_(3)reinforced Sn_(1.0)Ag_(0.5)Cu(SAC105)composite solder was prepar...Dopamine polymerization reaction and hydrothermal method were used to prepare nickel coated Al_(2)O_(3)reinforcement phase(Ni/Al_(2)O_(3)).Ni/Al_(2)O_(3)reinforced Sn_(1.0)Ag_(0.5)Cu(SAC105)composite solder was prepared using traditional casting method.The result shows that the nickel coating layer is continuous with uneven thickness.The interface between nickel and aluminum oxide exhibits a metallurgical bonding with coherent interface relationship.The strength,toughness and wettability of the SAC105 solder on the substrate are improved,while the conductivity is not decreased significantly.The fracture mode of composites transitions from a mixed toughness-brittleness mode to a purely toughness-dominated mode,characterized by many dimples.The prepared composite brazing material was made into solder paste for copper plate lap joint experiments.The maximum shear strength is achieved when the doping amount was 0.3wt%.The growth index of intermetallic compound at the brazing interface of Ni/Al_(2)O_(3)reinforced SAC105 composite solder is linearly fitted to n=0.39,demonstrating that the growth of intermetallic compound at the interface is a combined effect of grain boundary diffusion and bulk diffusion.展开更多
High entropy alloy composites(HEACs)are a new class of metal matrix composites involving a second phase,such as carbides,borides,and nitrides in high entropy alloy matrices.In recent years,HEACs have attracted wide at...High entropy alloy composites(HEACs)are a new class of metal matrix composites involving a second phase,such as carbides,borides,and nitrides in high entropy alloy matrices.In recent years,HEACs have attracted wide attention due to their outstanding properties.However,the preparation of HEACs encounters great challenges when using conventional casting approaches due to serious composition segregation.3D printing techniques solved this problem and produced components with complex geometry.Therefore,3D printing techniques have been applied to fabricating HEAC components,and a few works on this topic have been published.To accommodate the rapid development of 3D printing of HEACs,we present a state-of-the-art overview of the recent progress of HEAC 3D printing.The article begins with an introduction of HEAs and 3D-printed HEACs.The processes of HEAC powders development,including gas atomization and mechanical alloying,are presented.The 3D printing processes of HEAC powders,such as powder bed fusion and directed metal deposition,and their microstructures are discussed.The mechanical properties of 3D-printed HEACs are discussed and compared with 3D-printed HEAs and their casting counterparts,and their hardness,resistance to wear,corrosion,and oxidation are discussed.Finally,new perspectives are outlined for future research.展开更多
Copper matrix composites(CMCs)offer promising applications by combining the functional characteristics of copper with composite phases.With the rapid advancement in aerospace,microelectronics,and intelligent terminal ...Copper matrix composites(CMCs)offer promising applications by combining the functional characteristics of copper with composite phases.With the rapid advancement in aerospace,microelectronics,and intelligent terminal engineering,the demand for CMCs with superior mechanical and electrical properties has become increasingly critical.This paper reviews the design principles,preparation methods,microstructures and properties of some typical CMCs.The existing form of composite phases in the Cu matrix and their effects on microstructure evolution and comprehensive properties are summarised.Key underlying mechanisms governing these enhancements are discussed.The results provide a systematic understanding of the relationship between reinforcement phases and properties,offering insights for the future development of CMCs aimed to achieve much better comprehensive properties.The paper concludes by outlining the development trends and future outlook for the application of CMCs.展开更多
Municipal solid waste （MSW） and its disposal are gaining significant importance in geotechnical and geoenvironmental engineering. However, conventional research is primarily focused on fresh MSW or MSW that is compa...Municipal solid waste （MSW） and its disposal are gaining significant importance in geotechnical and geoenvironmental engineering. However, conventional research is primarily focused on fresh MSW or MSW that is compacted under its own weight in the landfill. In this work, a series of tests to study the properties of a densified MSW after ground treatment were presented. The tests involved oedometer test, simple shear test, triaxial shear test, and permeability test, which were conducted to investigate the compressibility, shear strength, creep behavior and permeability of the MSW. The results show that the compressibility modulus of the MSW increases as the dry density increases. However, the influence of density on modulus decreases once the density reaches a certain value. Like most soils, the stress-strain curve of the densified MSW can be approximated by a hyperbola in the triaxial shear test. Fibrous components provide additional cohesion for MSW, but have a relatively smaller effect on friction angle. Permeability is also found to be closely related to the dry density of the MSW, i.e., MSW with a higher dry density has a smaller permeability. The permeability coefficient may be less than 10 7 cm/s if the density is high enough.展开更多
文摘Heat-resistant aluminum alloys are widely used in aerospace and automotive fields for manufacturing hot components due to their advantages in lightweight design and energy conservation.However,the high-temperature strength of existing cast aluminum alloys is always limited to about 100 MPa at 350℃due to coarsening and transformation of strengthening phases.Here,we reveal that the yield strength and ultimate tensile strength of the T6 state Al-8.4Cu-2.3Ce-1.0Mn-0.5Ni-0.2Zr alloy at 400◦C increase by 34%and 44%after re-aging at 300℃for 100 h,and its thermal strength exhibits distinguished ad-vantage over traditional heat-resistant aluminum alloys.The enhanced elevated-temperature strength is attributed to the reprecipitation of the Ni-bearing T-Al_(20)Cu_(2)Mn_(3)phase,whose number density increases over one time.The significant segregation of Ni,Ce,and Zr elements at the interfaces helps improve the thermal stability of the T phase.The thermostable T phase effectively strengthens the matrix by in-hibiting dislocation motion.Meanwhile,a highly interconnected 3D intermetallic network along the grain boundaries can still remain after long-term re-aging at 300℃,which is conducive to imposing a drag on the grain boundaries at high temperatures.This finding offers a viable route for enhancing the elevated-temperature strength of heat-resistant aluminum alloys,which could provide expanded opportunities for higher-temperature applications.
基金support provided by the National Natural Science Foundation of China(No.52174357)Fundamental Research Funds for the Central Universities(No.DUT21LAB132)The Basic and Applied Basic Research Major Programme of Guangdong Province,China(No.2021B0301030003)。
文摘This study investigates the impact of Zn alloying on the dispersion of the reinforcing particle in Mg_(2)Sn/Mg composites.In the composite,Zn manifests in three distinct forms:Zn segregation layer between Mg–Mg_(2)Sn,the solid solution and the MgZn_(2)phase.First-principles calculations confirm that the formation of Zn segregation layer decreases the interfacial energy of the Mg–Mg_(2)Sn.Importantly,this segregation layer significantly enhances the comigration capability of Mg_(2)Sn particles with Mg matrix during sintering flow,effectively hindering the agglomeration and coarsening of the nano-sized reinforcing phase.The dense and uniformly distributed nano-sized Mg_(2)Sn significantly increases the activity of non-basal slip,ensuring good elongation of the composite while enhancing strength.It can be concluded that enhancing the comigration-ability of reinforcing particles with the matrix is an effective strategy for achieving controlled dispersion of high-volume reinforcing particles and an excellent combination of strength and ductility in magnesium matrix composites.
基金ational Natural Science Foundation of China(U1604132)Central Plains Talents Program-Fund of Central Plains Leading Talents(ZYYCYU002130)+1 种基金Key Technology Research and Development Program of Henan Province(222102230114)Major Scientific Research Foundation of Higher Education of Henan Province(23B430003)。
文摘Dopamine polymerization reaction and hydrothermal method were used to prepare nickel coated Al_(2)O_(3)reinforcement phase(Ni/Al_(2)O_(3)).Ni/Al_(2)O_(3)reinforced Sn_(1.0)Ag_(0.5)Cu(SAC105)composite solder was prepared using traditional casting method.The result shows that the nickel coating layer is continuous with uneven thickness.The interface between nickel and aluminum oxide exhibits a metallurgical bonding with coherent interface relationship.The strength,toughness and wettability of the SAC105 solder on the substrate are improved,while the conductivity is not decreased significantly.The fracture mode of composites transitions from a mixed toughness-brittleness mode to a purely toughness-dominated mode,characterized by many dimples.The prepared composite brazing material was made into solder paste for copper plate lap joint experiments.The maximum shear strength is achieved when the doping amount was 0.3wt%.The growth index of intermetallic compound at the brazing interface of Ni/Al_(2)O_(3)reinforced SAC105 composite solder is linearly fitted to n=0.39,demonstrating that the growth of intermetallic compound at the interface is a combined effect of grain boundary diffusion and bulk diffusion.
基金financially supported by the National Natural Science Foundation of China(No.52061160483)。
文摘High entropy alloy composites(HEACs)are a new class of metal matrix composites involving a second phase,such as carbides,borides,and nitrides in high entropy alloy matrices.In recent years,HEACs have attracted wide attention due to their outstanding properties.However,the preparation of HEACs encounters great challenges when using conventional casting approaches due to serious composition segregation.3D printing techniques solved this problem and produced components with complex geometry.Therefore,3D printing techniques have been applied to fabricating HEAC components,and a few works on this topic have been published.To accommodate the rapid development of 3D printing of HEACs,we present a state-of-the-art overview of the recent progress of HEAC 3D printing.The article begins with an introduction of HEAs and 3D-printed HEACs.The processes of HEAC powders development,including gas atomization and mechanical alloying,are presented.The 3D printing processes of HEAC powders,such as powder bed fusion and directed metal deposition,and their microstructures are discussed.The mechanical properties of 3D-printed HEACs are discussed and compared with 3D-printed HEAs and their casting counterparts,and their hardness,resistance to wear,corrosion,and oxidation are discussed.Finally,new perspectives are outlined for future research.
基金support by the Key-Area Research and Development Program of Guangdong Province,China(No.2024B0101080003)Hunan Provincial Natural Science Foundation of China(No.2024JJ2076)grants from the State Key Laboratory of Powder Metallurgy,Central South University,China.
文摘Copper matrix composites(CMCs)offer promising applications by combining the functional characteristics of copper with composite phases.With the rapid advancement in aerospace,microelectronics,and intelligent terminal engineering,the demand for CMCs with superior mechanical and electrical properties has become increasingly critical.This paper reviews the design principles,preparation methods,microstructures and properties of some typical CMCs.The existing form of composite phases in the Cu matrix and their effects on microstructure evolution and comprehensive properties are summarised.Key underlying mechanisms governing these enhancements are discussed.The results provide a systematic understanding of the relationship between reinforcement phases and properties,offering insights for the future development of CMCs aimed to achieve much better comprehensive properties.The paper concludes by outlining the development trends and future outlook for the application of CMCs.
基金Foundation item： Project（50979047） supported by the National Natural Science Foundation of China Project（2010CB732103） supported by the National Basic Research Program of China Project（2012-KY-02） supported by the State Key Laboratory of Hydroscience and Engineering （Tsinghua University）, China
文摘Municipal solid waste （MSW） and its disposal are gaining significant importance in geotechnical and geoenvironmental engineering. However, conventional research is primarily focused on fresh MSW or MSW that is compacted under its own weight in the landfill. In this work, a series of tests to study the properties of a densified MSW after ground treatment were presented. The tests involved oedometer test, simple shear test, triaxial shear test, and permeability test, which were conducted to investigate the compressibility, shear strength, creep behavior and permeability of the MSW. The results show that the compressibility modulus of the MSW increases as the dry density increases. However, the influence of density on modulus decreases once the density reaches a certain value. Like most soils, the stress-strain curve of the densified MSW can be approximated by a hyperbola in the triaxial shear test. Fibrous components provide additional cohesion for MSW, but have a relatively smaller effect on friction angle. Permeability is also found to be closely related to the dry density of the MSW, i.e., MSW with a higher dry density has a smaller permeability. The permeability coefficient may be less than 10 7 cm/s if the density is high enough.
