Interfacial Microstructure And Mechanical Properties Of TC11 Alloy And Ti₃SiC₂ Ceramic Diffusion Bonded Joint

Ti₃SiC₂ ceramic has the excellent characteristics of ceramics and metals,good electrical and thermal conductivity,thermal shock resistance and excellent corrosion resistance,which has been considered as promising materials in aerospace and nuclear energy fields.TC11 alloy is widely used in aerospace and nuclear energy fields because of its low modulus of elasticity and high corrosion resistance.Well-bonded Ti₃SiC₂ceramic and TC11 alloy joint can widen the application fields of the two materials.In this paper,a method of diffusion bonding of Tiand Cu intermediate layers is proposed to obtain a joint diffusion bonded with excellent mechanical properties.The formation process and mechanism of the diffusion joint are analyzed.When the Ti₃SiC₂ ceramic are bonded using a Tiintermediate layer,it is found that microcracks appear at the joint interface with the increase of diffusion temperature and holding time.The shear strength first increases then decreases with the increase of bonding temperature,holding time and the thickness of Tiinterlayer.The typical microstructure of the Ti₃SiC₂/Ti/Ti₃SiC₂joint was obtained at 1100℃with a 60-μm thick Tifoil for 60min under 20MPa consisted of Ti₃SiC₂/Ti₅Si₃C_x/TiSi/Ti₅Si₄/TiAl₂/TiAl/Ti₃Al/α-Ti/Ti₃Al/TiAl/TiAl₂/Ti₅Si₄/TiSi/Ti₅Si₃C_x/Ti₃SiC₂,the maximum shear strength,174MPa,and the fracture occurs in the Ti-Si compound layer and the base material.When the Ti₃SiC₂ ceramic and the TC11 alloy are diffusion-bonded,it is difficult to form a joint diffusion bonded without defects by direct diffusion bonding.When the diffusion bonding using a Tiintermediate layer is adopted,the shear strength of the joint increases with the increase of the bonding temperature and the holding time,and then increases and decreases.When the diffusion temperature was 950℃,the typical interface structure of the joint obtained by diffusion bonding using a 60μm thick Tiintermediate layer is:TC11/α-Ti/Ti₃Al/TiAl/TiAl₂/TiAl₃/Ti₅Si₄/TiSi/Ti₅Si₃C_x/Ti₃SiC₂.The joint obtained by diffusion bonding has the highest shear strength,143MPa.After shearing,the fracture occurs in the Ti₅Si₄ and TiSi diffusion layers.In order to eliminate the weak Ti-Si diffusion layer,a Cu intermediate layer is used for diffusion bonding of the Ti₃SiC₂ ceramic and the TC11 alloy.The diffusion bonding temperature is lowered to prevent coarsening of the TC11 alloy structure.A typical interfacial organization can be divided into three regions,a Ti-Cu compound region,a Ti-Si compound region,and a Cu（s,s）region.With the increase of bonding temperature and the prolonging of holding time,the shear strength of joints first increases and then decreases.The maximum shear strength,251MPa,obtained by the joint diffusion bonded at 850°C for 60min under 10MPa using a 50-μm Cu interlayer.The fracture occurred in the Cu（s,s）layer.