Refractory high-entropy alloys have recently emerged as promising candidates for high-temperature structural applications.However,their performance is compromised by the trade-off required between strength and ductili...Refractory high-entropy alloys have recently emerged as promising candidates for high-temperature structural applications.However,their performance is compromised by the trade-off required between strength and ductility.Here,a novel W30Ta5(FeNi)65 refractory high-entropy alloy with an outstanding combination of strength and plasticity at both room and elevated temperatures is designed,based on the multi-phase transitions design strategy.The alloy comprises a body-centered cubic dendrite phase,a topologically close-packed μ rhombohedral phase,and a high-density coherent nano-precipitate γ"phase with the D0_(22)structure(Ni3Ta type)embedded in a continuous face-centered cubic matrix.Owing to pre-cipitation strengthening of D0_(22),the yield stress of the alloy is determined as high as 1450 MPa,which is a significant improvement(~100%)in comparison with the D0_(22)-free alloy,without a loss of ductil-ity.This alloy exhibits an excellent high-temperature strength,with the yield strengths of 1300 MPa at 600 ℃ and 320 MPa at 1000 ℃.Detailed microstructural characterization using transmission electron mi-croscopy,high-angle annular dark-field imaging,and three-dimensional atom probe tomography analyses indicated that this superior strength-plasticity combination stems from the synergy of a multiple-phase structure.These results provide a new insight into the design of RHEAs and other advanced alloys.展开更多
To improve the yield strength of metallic materials at low temperatures,a strategy of combining the calculation of phase diagrams(CALPHAD)technique with the overall valence electron concentration(OVEC)principle is app...To improve the yield strength of metallic materials at low temperatures,a strategy of combining the calculation of phase diagrams(CALPHAD)technique with the overall valence electron concentration(OVEC)principle is applied,and a Ni_(2)CoCrNb_(0.2)medium-entropy alloy(MEA)with D022 superlattice(noted as theγ″phase)is designed.Bulk MEA samples without defects were successfully fabricated using laser additive manufacturing(AM),followed by solution treatment at 1200℃for 1 h and then aging at 650℃for 120 h.The nanoscaleγ″phase precipitated.The tensile results indicated that the MEA had superior yield strengths of∼1180 MPa and∼1320 MPa and tensile strengths of∼1335 MPa and∼1552 MPa at 293 K and 77 K,respectively.The yield strength obtained was superior to that of currently reported medium/high-entropy alloys and typical advanced cryogenic steel.The mechanical properties of the Ni_(2)CoCrNb_(0.2)MEA demonstrated a strong temperature dependence,and the increased yield strength was mainly attributed to the increase in lattice friction stress at low temperatures.This research provides a new strategy for producing materials with ultrastrong cryogenic yield strengths by AM.展开更多
基金National Natural Science Foundation of China(Nos.11790292,11972346,12102433,U2141204 and 11988102)National Key Research and Development Program of China(No.2017YFB0702003)+4 种基金Strategic Priority Research Program(Nos.XDB22040302 and XDB22040303)Key Research Program of Frontier Sciences(No.QYZDJSSW-JSC011)Science Challenge Project(No.TZ2016001)Key Research Program of the Chinese Academy of Sciences(No.ZDRW-CN-2021-2-3)Opening Project of State Key Laboratory of Explosion Science and Technology(No.KFJJ21-01Z).
文摘Refractory high-entropy alloys have recently emerged as promising candidates for high-temperature structural applications.However,their performance is compromised by the trade-off required between strength and ductility.Here,a novel W30Ta5(FeNi)65 refractory high-entropy alloy with an outstanding combination of strength and plasticity at both room and elevated temperatures is designed,based on the multi-phase transitions design strategy.The alloy comprises a body-centered cubic dendrite phase,a topologically close-packed μ rhombohedral phase,and a high-density coherent nano-precipitate γ"phase with the D0_(22)structure(Ni3Ta type)embedded in a continuous face-centered cubic matrix.Owing to pre-cipitation strengthening of D0_(22),the yield stress of the alloy is determined as high as 1450 MPa,which is a significant improvement(~100%)in comparison with the D0_(22)-free alloy,without a loss of ductil-ity.This alloy exhibits an excellent high-temperature strength,with the yield strengths of 1300 MPa at 600 ℃ and 320 MPa at 1000 ℃.Detailed microstructural characterization using transmission electron mi-croscopy,high-angle annular dark-field imaging,and three-dimensional atom probe tomography analyses indicated that this superior strength-plasticity combination stems from the synergy of a multiple-phase structure.These results provide a new insight into the design of RHEAs and other advanced alloys.
基金National Natural Science Foundation of China(No.52164044)the Natural Science Foundation of Guizhou Province of China(No.2022[053])+1 种基金the Talent growth plan of Guizhou education department of China(No.[2022]137)the Plan of Key Laboratory of Advanced Manufacturing Technology of the Ministry of Education of Guizhou University,China(No.GZUAMT2021KF[12]).
文摘To improve the yield strength of metallic materials at low temperatures,a strategy of combining the calculation of phase diagrams(CALPHAD)technique with the overall valence electron concentration(OVEC)principle is applied,and a Ni_(2)CoCrNb_(0.2)medium-entropy alloy(MEA)with D022 superlattice(noted as theγ″phase)is designed.Bulk MEA samples without defects were successfully fabricated using laser additive manufacturing(AM),followed by solution treatment at 1200℃for 1 h and then aging at 650℃for 120 h.The nanoscaleγ″phase precipitated.The tensile results indicated that the MEA had superior yield strengths of∼1180 MPa and∼1320 MPa and tensile strengths of∼1335 MPa and∼1552 MPa at 293 K and 77 K,respectively.The yield strength obtained was superior to that of currently reported medium/high-entropy alloys and typical advanced cryogenic steel.The mechanical properties of the Ni_(2)CoCrNb_(0.2)MEA demonstrated a strong temperature dependence,and the increased yield strength was mainly attributed to the increase in lattice friction stress at low temperatures.This research provides a new strategy for producing materials with ultrastrong cryogenic yield strengths by AM.
