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A high entropy interlayer (TiZrHfNb)95Al5 was successfully designed for vacuum diffusion bonding of GH4169 superalloy to Ti2AlNb alloy. The relationships between grain size, grain boundary, lattice mismatch and microhardness, elastic modulus, shear strength and fracture behaviors were revealed. The typical microstructure was Ti2AlNb/B2/Solid solution/(Ti, Zr, Hf)2(Ni, Nb)+(Ti, Zr, Hf)(Ni, Nb) + Solid solution/(Ti, Zr, Hf)(Ni, Nb) + (Cr, Ni, Fe)ss/(Cr, Ni, Fe)ss/Cr-rich(Cr, Ni, Fe)ss/Ni-rich(Cr, Ni, Fe)ss/GH4169. With the holding time increased, the shear strength overall increased and decreased sharply, and the highest shear strength reached 384 MPa at 980 °C for 90 min. The microstructure had anisotropic crystal orientation, and the joints of Zone Ш for 90 min consisted of 92.08 % HAGBs and 7.92 % LAGBs. The residual strains and stresses decreased when the holding time increased. Meanwhile, recrystallisation appeared in Zone Ш, and the increase in the recrystallisation rate led to grain refinement. The lattice mismatch between (Ti, Zr, Hf)(Ni, Nb) and (Cr, Ni, Fe)ss phases was 25.05 %, indicating that the interface was non-coherent, and (Ti, Zr, Hf)(Ni, Nb)+(Cr, Ni, Fe)ss phases were located at an elastic modulus dramatically changed interface. Thus, the cracks easily formed in this interface and led to joint fracture. Moreover, the fracture mechanism was brittle fracture.

[Display omitted] • A high entropy interlayer (TiZrHfNb) 95 Al 5 was successfully designed for diffusion bonding of GH4169 to Ti 2 AlNb. • The relationships between grain characteristics, lattice mismatch and mechanical properties, fracture mechanisms were revealed. • The major cracks located at the elastic modulus dramatically changed interface, i.e., the no-coherent interface. • The highest shear strength reached 384 MPa at 980 °C for 90 min. A high entropy interlayer (TiZrHfNb) 95 Al 5 was successfully designed for vacuum diffusion bonding of GH4169 superalloy to Ti 2 AlNb alloy. The relationships between grain size, grain boundary, lattice mismatch and microhardness, elastic modulus, shear strength and fracture behaviors were revealed. The typical microstructure was Ti 2 AlNb/B2/Solid solution/(Ti, Zr, Hf) 2 (Ni, Nb)+(Ti, Zr, Hf)(Ni, Nb) + Solid solution/(Ti, Zr, Hf)(Ni, Nb) + (Cr, Ni, Fe) ss /(Cr, Ni, Fe) ss /Cr-rich(Cr, Ni, Fe) ss /Ni-rich(Cr, Ni, Fe) ss /GH4169. With the holding time increased, the shear strength overall increased and decreased sharply, and the highest shear strength reached 384 MPa at 980 °C for 90 min. The microstructure had anisotropic crystal orientation, and the joints of Zone Ш for 90 min consisted of 92.08 % HAGBs and 7.92 % LAGBs. The residual strains and stresses decreased when the holding time increased. Meanwhile, recrystallisation appeared in Zone Ш, and the increase in the recrystallisation rate led to grain refinement. The lattice mismatch between (Ti, Zr, Hf)(Ni, Nb) and (Cr, Ni, Fe) ss phases was 25.05 %, indicating that the interface was non-coherent, and (Ti, Zr, Hf)(Ni, Nb)+(Cr, Ni, Fe) ss phases were located at an elastic modulus dramatically changed interface. Thus, the cracks easily formed in this interface and led to joint fracture. Moreover, the fracture mechanism was brittle fracture. [ABSTRACT FROM AUTHOR]

A high entropy interlayer (TiZrHfNb) 95 Al 5 was designed for vacuum diffusion bonding of Ti 2 AlNb to GH4169. The influence of bonding temperature on the interfacial microstructure morphology, mechanical properties and fracture behaviour of the resultant joints was investigated. The evolution of microstructure and fracture mechanism were revealed. The typical interface microstructure of Ti 2 AlNb/B2/Solid solution/(Ti, Zr, Hf) 2 (Ni, Nb)+(Ti, Zr, Hf)(Ni, Nb)+(Ti, Zr, Hf)(Ni, Nb) 2 +Solid solution/(Ti, Zr, Hf)(Ni, Nb)+(Cr, Ni, Fe) ss /(Cr, Ni, Fe) ss /Cr-rich(Cr, Ni, Fe) ss /Ni-rich(Cr, Ni, Fe) ss /GH4169 was formed. As the bonding temperature increased, the thickness of interfacial reaction layer gradually increased, and the shear strength gradually increased until 980 °C, then decreased sharply. The highest shear strength reached 376 MPa at 980 °C for 90 min. The highest microhardness region of 11.79 GPa existed on the GH4169 side, which was mainly composed of (Ti, Zr, Hf)(Ni, Nb) and (Cr, Ni, Fe) ss phases. Meanwhile, the elastic modulus dramatically changed interface formed near this region. The fracture surface morphology indicated typical brittle fracture characteristics such as cleavage steps, transgranular fracture and intergranular fracture. According to the fracture analyses, major cracks initiated in the (Ti, Zr, Hf)(Ni, Nb) phase+(Ti, Zr, Hf) 2 (Ni, Nb) phase and gradually extended to the (Cr, Ni, Fe) ss phase. Thus, the major crack emerged region was located at the elastic modulus dramatically changed interface. • Ti 2 AlNb alloy was diffusion bonded to GH4169 alloy by using (TiZrHfNb) 95 Al 5 high entropy interlayer. • The maximum shear strength of 376 MPa reached in the bonding temperature of 980 °C and holding time of 90 min. • The relationship between the interfacial microstructure and the fracture behaviour was examined. • The major crack emerged region was located at the elastic modulus dramatically changed interface. [ABSTRACT FROM AUTHOR]