The intrinsic properties of theγ′phase are well known to be of critical importance for the targeted control of the mechanical performance ofγ/γ′high entropy alloys(HEAs).In the present work,a composition tuning s...The intrinsic properties of theγ′phase are well known to be of critical importance for the targeted control of the mechanical performance ofγ/γ′high entropy alloys(HEAs).In the present work,a composition tuning strategy is employed to modulate the thermal stability,elastic properties,and deformation mechanisms of theγ′phase in(FeCoNi)86Ti7Al7 HEAs using ab initio methods.Prior to tailoring the alloying elements,the temperature-dependent stability of theγ′phase is meticulously investigated by considering both enthalpic and entropic contributions.The findings reveal that the primary vibrational entropy can be effectively substituted by an empirical parameter(δ)to expedite the design of stable HEAs.Subsequently,based on the individual effects of elements on the order-disorder transformation temperatures(Tod)and practical considerations for high-temperature applications,eight substituting elements(Nb,Mo,Ta,W,V,Cr,Mn and Cu)are judiciously selected from the 3d,4d and 5d transition metal series.The results indicate that Nb and Ta are the most ideal substituting elements for theγ′phase,as they concurrently enhance the Tod,shear modulus,hardness,ductility,and antiphase boundary energy.These insights open a promising avenue for the innovative design of strong-yet-ductileγ/γ′HEAs.展开更多
High entropy alloy(HEA) of Fe Co Ni Ti Al and Inconel 718 superalloy were firstly transient liquid phase(TLP) bonded by BNi2 filler due to the diffusion of Si and B in the filler to the base metals. The effects of bon...High entropy alloy(HEA) of Fe Co Ni Ti Al and Inconel 718 superalloy were firstly transient liquid phase(TLP) bonded by BNi2 filler due to the diffusion of Si and B in the filler to the base metals. The effects of bonding time on microstructure evolution and mechanical properties of the TLP joints were investigated.Owing to the complete isothermal solidification of the joints bonded for 30 min 120 min at 1100°C,no athermally solidified zones(ASZs) formed by eutectic phases were observed in the welded zone. Thus the TLP joints were only composed by the isothermally solidified zone(ISZ) and two diffusion affected zone(DAZ) adjacent to the dissimilar base metals and the negative effect of the ASZ on joint properties can be avoided. In addition, the increase of the bonding time can also make the Ti B2 borides precipitated in the DAZ near HEA and the brittle borides or carbides in the DAZ near IN718 alloy decrease and reduce the possibility of the stress concentration happened in the joints under loading. Therefore, the highest shear strength(632.1 MPa) of the TLP joints was obtained at 1100°C for 120 min, which was higher than that of the joint bonded for 30 min, 404.2 MPa. Furthermore, the extension of the bonding time made the fracture mechanism of the joint be transformed from the intergranular fracture to the transgranular fracture. However, as the brittle borides in the DAZ near IN718 can not be eliminated completely and refining of grains also happened in such region, all the TLP joints fractured inner the DAZ near IN718 alloy.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52371014 and U22B20132)Shenzhen Science and Technology Program(No.JCYJ20230807091401004)+1 种基金Fundamental Research Funds for the Central Universities(No.20720230036)Guided Subject of Dean’s Fund(No.YZJJ-YDL-0004).
文摘The intrinsic properties of theγ′phase are well known to be of critical importance for the targeted control of the mechanical performance ofγ/γ′high entropy alloys(HEAs).In the present work,a composition tuning strategy is employed to modulate the thermal stability,elastic properties,and deformation mechanisms of theγ′phase in(FeCoNi)86Ti7Al7 HEAs using ab initio methods.Prior to tailoring the alloying elements,the temperature-dependent stability of theγ′phase is meticulously investigated by considering both enthalpic and entropic contributions.The findings reveal that the primary vibrational entropy can be effectively substituted by an empirical parameter(δ)to expedite the design of stable HEAs.Subsequently,based on the individual effects of elements on the order-disorder transformation temperatures(Tod)and practical considerations for high-temperature applications,eight substituting elements(Nb,Mo,Ta,W,V,Cr,Mn and Cu)are judiciously selected from the 3d,4d and 5d transition metal series.The results indicate that Nb and Ta are the most ideal substituting elements for theγ′phase,as they concurrently enhance the Tod,shear modulus,hardness,ductility,and antiphase boundary energy.These insights open a promising avenue for the innovative design of strong-yet-ductileγ/γ′HEAs.
基金supported by the research fund of the State Key Laboratory of Solidification Processing(NWPU,China)(Grant No.2019-TS-09)the National Natural Science Foundations of China(Grant Nos.51975480,51575451,51475376 and U1737205)。
文摘High entropy alloy(HEA) of Fe Co Ni Ti Al and Inconel 718 superalloy were firstly transient liquid phase(TLP) bonded by BNi2 filler due to the diffusion of Si and B in the filler to the base metals. The effects of bonding time on microstructure evolution and mechanical properties of the TLP joints were investigated.Owing to the complete isothermal solidification of the joints bonded for 30 min 120 min at 1100°C,no athermally solidified zones(ASZs) formed by eutectic phases were observed in the welded zone. Thus the TLP joints were only composed by the isothermally solidified zone(ISZ) and two diffusion affected zone(DAZ) adjacent to the dissimilar base metals and the negative effect of the ASZ on joint properties can be avoided. In addition, the increase of the bonding time can also make the Ti B2 borides precipitated in the DAZ near HEA and the brittle borides or carbides in the DAZ near IN718 alloy decrease and reduce the possibility of the stress concentration happened in the joints under loading. Therefore, the highest shear strength(632.1 MPa) of the TLP joints was obtained at 1100°C for 120 min, which was higher than that of the joint bonded for 30 min, 404.2 MPa. Furthermore, the extension of the bonding time made the fracture mechanism of the joint be transformed from the intergranular fracture to the transgranular fracture. However, as the brittle borides in the DAZ near IN718 can not be eliminated completely and refining of grains also happened in such region, all the TLP joints fractured inner the DAZ near IN718 alloy.
