An extremely high-strength TiAl/Ni-based superalloy dissimilar joint was obtained using a designed Ni_(25)Zr_(25)Sn_(20)Cu_(10)Hf_(10)Cr_(5)Fe_(5)multi-principal element interlayer via contact reaction brazing.It was ...An extremely high-strength TiAl/Ni-based superalloy dissimilar joint was obtained using a designed Ni_(25)Zr_(25)Sn_(20)Cu_(10)Hf_(10)Cr_(5)Fe_(5)multi-principal element interlayer via contact reaction brazing.It was found that a joint mainly composed of eutectic structure of(Ni)ss,(Ni,Cr,Fe)ss,and(Cr,Ni,Fe,Mo)ss,as well as micro-nano precipitates of(Ti)ss and(Hf,Zr)ss,could be achieved through the interaction between the interlayer and the base metals.The joint exhibited a shear strength of 498 MPa when brazed at 1190°C for 10 min,while the fracture occurred within the TiAl base metal,and the retention rate of high-temperature(HT)strength(650°C)was∼100%.The strengthening mechanism of the brazed joint was systematically discussed by transmission electron microscopy(TEM).It was shown that high-density dis-locations existed in each phase of the seam as well as twinning and stacking faults existed in the micro-nano precipitates,caused by a mass of solute atoms,greatly strengthened the joint.At HTs,the dislocation strengthening effect weakened due to grain recovery and recrystallization,but the joint could be addi-tionally toughened by multi-cracking.Meanwhile,granular(Ti)ss dispersed through the seam and ductile reticular structure(Ni)ss toughened the joint via the mechanism of crack termination and bridging.The proposed method provides a new approach for high strength and heat resistance joining of TiAl/Ni-based superalloy in aeroengine components.展开更多
In the present paper, the influence of carbon nanofiber on interlaminar fracture toughness of CFRP investigated using MMB（Mixed Mode Bending） tests. Vapor grown carbon fiber VGCF and VGCF-S, and multi-walled carbon ...In the present paper, the influence of carbon nanofiber on interlaminar fracture toughness of CFRP investigated using MMB（Mixed Mode Bending） tests. Vapor grown carbon fiber VGCF and VGCF-S, and multi-walled carbon nanotube MWNT-7 has been employed for the toughener of the interlayer on the CFRP laminates. In order to evaluate the fracture toughness and mixed mode ratio of it, double cantilever beam （DCB） tests, end notched fracture （ENF） tests and mixed mode bending （MMB） tests have been carried out. Boundary element analysis was applied to the CFRP model to compute the interlaminar fracture toughness, where extrapolation method was used to determine the fracture toughness and mixed mode ratio. The interlaminar fracture toughness and mixed mode ratio can be extrapolated by stress distribution in the vicinity of the crack tip of the CFRP laminate. It was found that the interlaminar fracture toughness of the CFRP laminates was improved inserting the interlayer made by carbon nanofiber especially in the region where shear mode deformation is dominant.展开更多
基金the financial support from the“National Natural Science Foundation of China(NSFC,Grant Nos.51974101,51975150,U21A20128,52175302 and U22A20185)”“National MCF Energy R&D Program(No.2019YFE03100100)”+1 种基金“Fundamental Research Funds for the Central Universities(Nos.2022FRFK060009 and HIT.DZJJ.2023011)”“Natural Science Foundation of Heilongjiang Province,China(No.JQ2020E003)”.
文摘An extremely high-strength TiAl/Ni-based superalloy dissimilar joint was obtained using a designed Ni_(25)Zr_(25)Sn_(20)Cu_(10)Hf_(10)Cr_(5)Fe_(5)multi-principal element interlayer via contact reaction brazing.It was found that a joint mainly composed of eutectic structure of(Ni)ss,(Ni,Cr,Fe)ss,and(Cr,Ni,Fe,Mo)ss,as well as micro-nano precipitates of(Ti)ss and(Hf,Zr)ss,could be achieved through the interaction between the interlayer and the base metals.The joint exhibited a shear strength of 498 MPa when brazed at 1190°C for 10 min,while the fracture occurred within the TiAl base metal,and the retention rate of high-temperature(HT)strength(650°C)was∼100%.The strengthening mechanism of the brazed joint was systematically discussed by transmission electron microscopy(TEM).It was shown that high-density dis-locations existed in each phase of the seam as well as twinning and stacking faults existed in the micro-nano precipitates,caused by a mass of solute atoms,greatly strengthened the joint.At HTs,the dislocation strengthening effect weakened due to grain recovery and recrystallization,but the joint could be addi-tionally toughened by multi-cracking.Meanwhile,granular(Ti)ss dispersed through the seam and ductile reticular structure(Ni)ss toughened the joint via the mechanism of crack termination and bridging.The proposed method provides a new approach for high strength and heat resistance joining of TiAl/Ni-based superalloy in aeroengine components.
基金supported by the Program for Fostering Regional Innovation in Nagano, granted by MEXT, Japan
文摘In the present paper, the influence of carbon nanofiber on interlaminar fracture toughness of CFRP investigated using MMB（Mixed Mode Bending） tests. Vapor grown carbon fiber VGCF and VGCF-S, and multi-walled carbon nanotube MWNT-7 has been employed for the toughener of the interlayer on the CFRP laminates. In order to evaluate the fracture toughness and mixed mode ratio of it, double cantilever beam （DCB） tests, end notched fracture （ENF） tests and mixed mode bending （MMB） tests have been carried out. Boundary element analysis was applied to the CFRP model to compute the interlaminar fracture toughness, where extrapolation method was used to determine the fracture toughness and mixed mode ratio. The interlaminar fracture toughness and mixed mode ratio can be extrapolated by stress distribution in the vicinity of the crack tip of the CFRP laminate. It was found that the interlaminar fracture toughness of the CFRP laminates was improved inserting the interlayer made by carbon nanofiber especially in the region where shear mode deformation is dominant.
