First-principles thermodynamic calculations were carried out at the interface level for understanding the precipitation of coherent L12-phase nano-structures in dilute Al–Sc–Er alloys.All energetics,relevant to bulk...First-principles thermodynamic calculations were carried out at the interface level for understanding the precipitation of coherent L12-phase nano-structures in dilute Al–Sc–Er alloys.All energetics,relevant to bulk substitution,interface formation,interfacial coherent strain and segregation,were calculated and used to evaluate the nucleation and relative stabilities of various possible L12 nano-structures.Only matrix-dissolved solute Er(or Sc)can substitute Sc(or Er)in L12-Al3Sc(or Al3Er).The inter-substitution between L12-Al3Sc and Al3Er is not energy feasible.Ternary L12-Al3(Er x Sc 1.x)precipitates tend to form the Al3Er-core and Al3Sc-shell structure with a sharp core/shell interface.Three possible formation mechanisms were proposed and examined.The eff ects of Er/Sc ratio and aging temperature on the relative stabilities of L12-phase nanostructures in Al were also discussed.展开更多
Precipitation-hardening in fcc-based high-entro py alloys(HEAs)have usually been realized by introducing complex intermetallic compounds.In this study,enhanced strength is ascribed to the existence of L1_(2) precipita...Precipitation-hardening in fcc-based high-entro py alloys(HEAs)have usually been realized by introducing complex intermetallic compounds.In this study,enhanced strength is ascribed to the existence of L1_(2) precipitates and B2/bcc conjoint phases in the fcc matrix.The nano-size particles in the Al_(0.5)CoCrFeNi HEA are produced by cold-rolling,followed by intermediate-temperature-annealing at 650℃.For L1_(2) ordering,the initial granular structure has transformed into lamella structure and then kept stable when the holding time prolonged to 200 h.The formation of this conjoint B2/bcc driven by the concentration profiles takes place when the diffusion process of elements is sufficient after long-time aging.Based on the microstructure analysis,changes in mechanical properties are associated with the shape,size scale and volume fraction of the precipitates.The peak ultimate tensile stress reaches 1221.5 MPa,1.97 times compared with the as-cast alloy,remaining plasticity of 21.3%.展开更多
Precipitation strengthening is a pivotal mechanism for enhancing the mechanical properties of low-density alloys.A detailed analysis of microstructural evolution during thermal processing is imperative to thoroughly u...Precipitation strengthening is a pivotal mechanism for enhancing the mechanical properties of low-density alloys.A detailed analysis of microstructural evolution during thermal processing is imperative to thoroughly understand its strengthening behavior.This study employed the Bähr D805L quenching dilatometer system to study the formation,evolution,and impact on the contribution of nano-precipitates on the mechanical behavior of Fe-21Mn-10Al-5Ni-C(nominal composition)low-density alloy during continuous cooling.The study unveiled the precipitation mechanism of nano-particles within the austenite(γ)matrix at cooling rates in the range of 40-0.1℃·s^(-1).Moreover,the addition of Ni in Fe-21Mn-10Al-5Ni-C low-density alloy enhances the atomic size factor,promoting alloy spinodal decomposition and ordering.During slow cooling,B2 phases precipitate along grain boundaries,accompanied by the formation of a precipitation-free zone(PFZ)near the boundaries and the dissolution of some later nucleated small particles.These phenomena are a primary mechanism that suppresses the precipitation of B2 phases within theγmatrix.展开更多
为了探讨C和Cu元素对Al0.3CoFeNi高熵合金微观组织及性能的影响,采用非自耗型真空电弧熔炼法制备了Al0.3CoFeNi,Al0.3CoFeNiC 0.1,(Al0.3CoFeNi)99.9 Cu 0.1和(Al0.3CoFeNiC 0.1)99.9 Cu 0.14种成分的高熵合金。运用X射线衍射仪测量合...为了探讨C和Cu元素对Al0.3CoFeNi高熵合金微观组织及性能的影响,采用非自耗型真空电弧熔炼法制备了Al0.3CoFeNi,Al0.3CoFeNiC 0.1,(Al0.3CoFeNi)99.9 Cu 0.1和(Al0.3CoFeNiC 0.1)99.9 Cu 0.14种成分的高熵合金。运用X射线衍射仪测量合金的晶体结构,采用扫描电镜和透射电镜观察合金的表面形貌和微观组织,利用万能试验机和维氏显微硬度计分别测试合金的压缩力学性能和显微硬度。试验结果表明:Al0.3CoFeNi高熵合金为单一的FCC结构,分别添加1%C和0.1%Cu(原子百分比y/%)均未改变其晶体结构,但合金中析出了纳米相L12相,且0.1%Cu的添加会使L12相的尺寸减小。仅添加1%C时,L12相的颗粒尺寸约为30nm,再添加0.1%Cu后,L12相的颗粒尺寸减小到10nm。力学性能测试结果表明,(Al0.3CoFeNiC 0.1)99.9 Cu 0.1合金的综合力学性能最好,其压缩屈服强度、抗压强度、压缩率和显微硬度分别可达为974 MPa、2532 MPa、51.9%和511.7HV。展开更多
Phase field model was employed to study the variations of interatomic potentials of Ni 3 Al (L1 2 phase) and Ni 3 V (DO 22 phase) as a function of temperature and concentration. The long-range order (LRO) parameter re...Phase field model was employed to study the variations of interatomic potentials of Ni 3 Al (L1 2 phase) and Ni 3 V (DO 22 phase) as a function of temperature and concentration. The long-range order (LRO) parameter related interatomic potentials equations formulated by Khachaturyan were utilized to establish the inversion equations for L1 2 and DO 22 phases, with which interatomic potentials could be calculated. The interatomic potentials of Ni-Al and Ni-V exhibited approximately linear increases and decreases, individually, with enhanced Al concentration. Substituting the inverted interatomic potentials into the microscopic phase field equations led to three cases of precipitation sequence: the DO 22 phase preceded L1 2 phase precipitating at the interatomic potentials of Ni-V > Ni-Al; the vice cases; and two phases precipitated simultaneously at interatomic potentials of Ni-V and Ni-Al were equal.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51971249)the National MCF Energy R&D Program of China(Project No.2018YFE0306100)the Key Research and Development Projects of Shandong Province(No.2017GGX20130)。
文摘First-principles thermodynamic calculations were carried out at the interface level for understanding the precipitation of coherent L12-phase nano-structures in dilute Al–Sc–Er alloys.All energetics,relevant to bulk substitution,interface formation,interfacial coherent strain and segregation,were calculated and used to evaluate the nucleation and relative stabilities of various possible L12 nano-structures.Only matrix-dissolved solute Er(or Sc)can substitute Sc(or Er)in L12-Al3Sc(or Al3Er).The inter-substitution between L12-Al3Sc and Al3Er is not energy feasible.Ternary L12-Al3(Er x Sc 1.x)precipitates tend to form the Al3Er-core and Al3Sc-shell structure with a sharp core/shell interface.Three possible formation mechanisms were proposed and examined.The eff ects of Er/Sc ratio and aging temperature on the relative stabilities of L12-phase nanostructures in Al were also discussed.
基金supported financially by the National Natural Science Foundation of China(Nos.51774240 and 51571161)the fund of the State Key Laboratory of Solidification Processing in NWPU(No.2019-TS-04)the National Training Program of Innovation and Entrepreneurship for Undergraduates(No.201910699109)。
文摘Precipitation-hardening in fcc-based high-entro py alloys(HEAs)have usually been realized by introducing complex intermetallic compounds.In this study,enhanced strength is ascribed to the existence of L1_(2) precipitates and B2/bcc conjoint phases in the fcc matrix.The nano-size particles in the Al_(0.5)CoCrFeNi HEA are produced by cold-rolling,followed by intermediate-temperature-annealing at 650℃.For L1_(2) ordering,the initial granular structure has transformed into lamella structure and then kept stable when the holding time prolonged to 200 h.The formation of this conjoint B2/bcc driven by the concentration profiles takes place when the diffusion process of elements is sufficient after long-time aging.Based on the microstructure analysis,changes in mechanical properties are associated with the shape,size scale and volume fraction of the precipitates.The peak ultimate tensile stress reaches 1221.5 MPa,1.97 times compared with the as-cast alloy,remaining plasticity of 21.3%.
基金supported by the CNPC Scientific Research and Technology Development Project(Nos.2021ZZ03,2023ZZ11,2022DQ03-02 and 2020B-4020).
文摘Precipitation strengthening is a pivotal mechanism for enhancing the mechanical properties of low-density alloys.A detailed analysis of microstructural evolution during thermal processing is imperative to thoroughly understand its strengthening behavior.This study employed the Bähr D805L quenching dilatometer system to study the formation,evolution,and impact on the contribution of nano-precipitates on the mechanical behavior of Fe-21Mn-10Al-5Ni-C(nominal composition)low-density alloy during continuous cooling.The study unveiled the precipitation mechanism of nano-particles within the austenite(γ)matrix at cooling rates in the range of 40-0.1℃·s^(-1).Moreover,the addition of Ni in Fe-21Mn-10Al-5Ni-C low-density alloy enhances the atomic size factor,promoting alloy spinodal decomposition and ordering.During slow cooling,B2 phases precipitate along grain boundaries,accompanied by the formation of a precipitation-free zone(PFZ)near the boundaries and the dissolution of some later nucleated small particles.These phenomena are a primary mechanism that suppresses the precipitation of B2 phases within theγmatrix.
文摘为了探讨C和Cu元素对Al0.3CoFeNi高熵合金微观组织及性能的影响,采用非自耗型真空电弧熔炼法制备了Al0.3CoFeNi,Al0.3CoFeNiC 0.1,(Al0.3CoFeNi)99.9 Cu 0.1和(Al0.3CoFeNiC 0.1)99.9 Cu 0.14种成分的高熵合金。运用X射线衍射仪测量合金的晶体结构,采用扫描电镜和透射电镜观察合金的表面形貌和微观组织,利用万能试验机和维氏显微硬度计分别测试合金的压缩力学性能和显微硬度。试验结果表明:Al0.3CoFeNi高熵合金为单一的FCC结构,分别添加1%C和0.1%Cu(原子百分比y/%)均未改变其晶体结构,但合金中析出了纳米相L12相,且0.1%Cu的添加会使L12相的尺寸减小。仅添加1%C时,L12相的颗粒尺寸约为30nm,再添加0.1%Cu后,L12相的颗粒尺寸减小到10nm。力学性能测试结果表明,(Al0.3CoFeNiC 0.1)99.9 Cu 0.1合金的综合力学性能最好,其压缩屈服强度、抗压强度、压缩率和显微硬度分别可达为974 MPa、2532 MPa、51.9%和511.7HV。
基金supported by the National Natural Science Foundation of China (10902086, 51075335 and 50875217)the Basic Research Fund of the Northwestern Polytechnical University (JC201005)the Doctoral Foundation of Northwestern Polytechnical University
文摘Phase field model was employed to study the variations of interatomic potentials of Ni 3 Al (L1 2 phase) and Ni 3 V (DO 22 phase) as a function of temperature and concentration. The long-range order (LRO) parameter related interatomic potentials equations formulated by Khachaturyan were utilized to establish the inversion equations for L1 2 and DO 22 phases, with which interatomic potentials could be calculated. The interatomic potentials of Ni-Al and Ni-V exhibited approximately linear increases and decreases, individually, with enhanced Al concentration. Substituting the inverted interatomic potentials into the microscopic phase field equations led to three cases of precipitation sequence: the DO 22 phase preceded L1 2 phase precipitating at the interatomic potentials of Ni-V > Ni-Al; the vice cases; and two phases precipitated simultaneously at interatomic potentials of Ni-V and Ni-Al were equal.
