Low-density superalloys often exhibit low yield strength in the intermediate temperature range(300−650℃).To enhance yield performance in this range,the CALPHAD method was used to design a new Co-based superalloy.The ...Low-density superalloys often exhibit low yield strength in the intermediate temperature range(300−650℃).To enhance yield performance in this range,the CALPHAD method was used to design a new Co-based superalloy.The Co−30Ni−10Al−3V−6Ti−2Ta alloy,designed based onγʹphase dissolution temperature and phase fraction,was synthesized via arc melting and heat treatment.Phase transition temperatures,microstructure evolution,and hightemperature mechanical properties were characterized by differential scanning calorimetry,scanning electron microscopy,dual-beam TEM,and compression tests.Results show that the alloy has low density(8.15 g/cm^(3))and highγʹdissolution temperature(1234℃),along with unique yield strength retention from room temperature to 650℃.The yield strength anomaly(YSA)is attributed to high stacking fault energy and activation of the Kear−Wilsdorf locking mechanism,contributing to superior high-temperature stability of the alloy.The yield strength of this alloy outperforms other lowdensity Co-based superalloys in the temperature range of 23−650℃.展开更多
The phase equilibria in the Co-Ti-Re ternary system at 800,1000,1100 and 12000C were studied combined with electron probe microanalyzer(EPMA),X-ray diffraction(XRD),scanning electron microscope(SEM)and transmission el...The phase equilibria in the Co-Ti-Re ternary system at 800,1000,1100 and 12000C were studied combined with electron probe microanalyzer(EPMA),X-ray diffraction(XRD),scanning electron microscope(SEM)and transmission electron microscope(TEM).The new phaseτwith a large solubility was discovered at all four isothermal sections,and its structure still needs a further study.A large solubility of Re in the CoTi phase was observed.The solubility of Re in the Co_(3)Ti phase is6.1%at 800℃,8.7%at 1000℃and 7.7%at 1100℃.The present work could be significant for alloy design of Co-based alloys and thermodynamic analysis of the Co-TiRe ternary system.展开更多
In order to investigate the formation mechanisms of the layered growth phenomena in diffusion couples with spinodal decomposition,a phase field model combined with elastic strain field was employed.Microstructure evol...In order to investigate the formation mechanisms of the layered growth phenomena in diffusion couples with spinodal decomposition,a phase field model combined with elastic strain field was employed.Microstructure evolutions of diffusion couple with spinodal decomposition in binary alloys were numerically simulated by considering concentration fluctuation and elastic anisotropy.The simulation results indicate that the number of the periodical layers decreases with the increase of initial concentration fluctuation,even with large elastic anisotropy.The growth of layered microstructures can be attributed to the directional diffusion enhanced by initially discontinuous chemical potential at the interface.展开更多
Phase diagrams of two isothermal sections of the Ni-Ti-Ta ternary system at 1000 and 1200℃in a full composition range were determined by X-ray diffraction and electron probe microanalysis.The experimental results ind...Phase diagrams of two isothermal sections of the Ni-Ti-Ta ternary system at 1000 and 1200℃in a full composition range were determined by X-ray diffraction and electron probe microanalysis.The experimental results indicated a ternary compoundτphase with low solid solubility and composition ranges of(16.3-22.4)at.%Ta,(15.9-24.1)at.%Ti and(58.5-60.0)at.%Ni at 1000℃.The two terminal solid solutions(bcc-(Ta)andβ-Ti)formed a continuous solid solution at 1000 and 1200℃.A certain amount of Ti can dissolve into Ni-Ta intermetallic compounds near the Ni-Ta side,with the highest value of 21.9 at.%observed in the Ni;Ta compound at 1000℃.展开更多
Isothermal sections of the Co−Al−Re ternary system at 1100 and 1300℃ were determined experimentally by electron probe microanalysis and X-ray diffraction.The results show that there are seven three-phase regions in t...Isothermal sections of the Co−Al−Re ternary system at 1100 and 1300℃ were determined experimentally by electron probe microanalysis and X-ray diffraction.The results show that there are seven three-phase regions in the 1100℃ isothermal section and five three-phase regions in the 1300℃ isothermal section.The solid solubilities ofαCo,εRe and CoAl increase a little with temperature increasing from 1100 to 1300℃.The solubility of Co in compounds AlRe2,Al11Re4 and Al4Re is negligible,<1.5 at.%.And no ternary compounds are found.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51831007,52101135)the Shenzhen Science and Technology Program,China(No.SGDX20210823104002016)the Guangdong Basic and Applied Basic Research Foundation,China(Nos.2021B1515120071,JCYJ20220531095217039)。
文摘Low-density superalloys often exhibit low yield strength in the intermediate temperature range(300−650℃).To enhance yield performance in this range,the CALPHAD method was used to design a new Co-based superalloy.The Co−30Ni−10Al−3V−6Ti−2Ta alloy,designed based onγʹphase dissolution temperature and phase fraction,was synthesized via arc melting and heat treatment.Phase transition temperatures,microstructure evolution,and hightemperature mechanical properties were characterized by differential scanning calorimetry,scanning electron microscopy,dual-beam TEM,and compression tests.Results show that the alloy has low density(8.15 g/cm^(3))and highγʹdissolution temperature(1234℃),along with unique yield strength retention from room temperature to 650℃.The yield strength anomaly(YSA)is attributed to high stacking fault energy and activation of the Kear−Wilsdorf locking mechanism,contributing to superior high-temperature stability of the alloy.The yield strength of this alloy outperforms other lowdensity Co-based superalloys in the temperature range of 23−650℃.
基金the Shenzhen Science and Technology Project,China(No.JCYJ20190809162401686)the Guangdong Basic and Applied Basic Research Foundation,China(No.2020A1515010069).
基金financially supported by the National Natural Science Foundation of China(No.51831007)the Key-area Research and Development Program of Guangdong Province(No.2019B010943001)。
文摘The phase equilibria in the Co-Ti-Re ternary system at 800,1000,1100 and 12000C were studied combined with electron probe microanalyzer(EPMA),X-ray diffraction(XRD),scanning electron microscope(SEM)and transmission electron microscope(TEM).The new phaseτwith a large solubility was discovered at all four isothermal sections,and its structure still needs a further study.A large solubility of Re in the CoTi phase was observed.The solubility of Re in the Co_(3)Ti phase is6.1%at 800℃,8.7%at 1000℃and 7.7%at 1100℃.The present work could be significant for alloy design of Co-based alloys and thermodynamic analysis of the Co-TiRe ternary system.
基金Project(2017YFB0702401) supported by the National Key R&D Program of ChinaProject(51301146) supported by the National Natural Science Foundation of ChinaProjects(20720170038,20720170048) supported by the Fundamental Research Funds for the Central Universities,China
文摘In order to investigate the formation mechanisms of the layered growth phenomena in diffusion couples with spinodal decomposition,a phase field model combined with elastic strain field was employed.Microstructure evolutions of diffusion couple with spinodal decomposition in binary alloys were numerically simulated by considering concentration fluctuation and elastic anisotropy.The simulation results indicate that the number of the periodical layers decreases with the increase of initial concentration fluctuation,even with large elastic anisotropy.The growth of layered microstructures can be attributed to the directional diffusion enhanced by initially discontinuous chemical potential at the interface.
基金financially supported by the National Natural Science Foundation of China(No.51831007)National Key R&D Program of China(No.2017YFB0702901)。
文摘Phase diagrams of two isothermal sections of the Ni-Ti-Ta ternary system at 1000 and 1200℃in a full composition range were determined by X-ray diffraction and electron probe microanalysis.The experimental results indicated a ternary compoundτphase with low solid solubility and composition ranges of(16.3-22.4)at.%Ta,(15.9-24.1)at.%Ti and(58.5-60.0)at.%Ni at 1000℃.The two terminal solid solutions(bcc-(Ta)andβ-Ti)formed a continuous solid solution at 1000 and 1200℃.A certain amount of Ti can dissolve into Ni-Ta intermetallic compounds near the Ni-Ta side,with the highest value of 21.9 at.%observed in the Ni;Ta compound at 1000℃.
基金financial supports from the National Natural Science Foundation of China(No.51831007)the National Key Research&Development Program of China(No.2017YFB0702901)。
文摘Isothermal sections of the Co−Al−Re ternary system at 1100 and 1300℃ were determined experimentally by electron probe microanalysis and X-ray diffraction.The results show that there are seven three-phase regions in the 1100℃ isothermal section and five three-phase regions in the 1300℃ isothermal section.The solid solubilities ofαCo,εRe and CoAl increase a little with temperature increasing from 1100 to 1300℃.The solubility of Co in compounds AlRe2,Al11Re4 and Al4Re is negligible,<1.5 at.%.And no ternary compounds are found.
