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
Femtosecond laser welding,a novel technique for material joining,faces challenges such as stringent pre-welding requirements and low joint strength when directly welding ceramics.In this study,we addressed the issues ...Femtosecond laser welding,a novel technique for material joining,faces challenges such as stringent pre-welding requirements and low joint strength when directly welding ceramics.In this study,we addressed the issues associated with the direct welding of yttria-stabilized zirconia(YSZ)and sapphire by first depositing a nanometer-thick Ti layer on the ceramic surface,followed by femtosecond laser welding.Notably,we observed for the first time that femtosecond laser pulses induced the formation of a honeycomb structure at the interface,forming a YSZ/sapphire micro-welding joint characterized by a continuous structure,a honeycomb structure,and Ti-rich phases.This specific joint distribution significantly enhanced the interface transition and improved the joint strength.Under conditions of 8 W laser power,scanning speed of 50 mm/s,and pulse frequency of 200 kHz,the micro-welding joint exhibited optimal interface performance,achieving a maximum shear strength of approximately 79 MPa.Through calculations of the temperature distribution of the interface and the surface energy of the crystal,we conclude that the honeycomb structure arises from the Ti layer,the temperature gradient distribution,and the tendency of sapphire to melt along directions with lower surface energy.The honeycomb structure effectively enriched the transition between the micro-welding interface and the substrate.The new findings of this study offer valuable insights and potential pathways for the reliable and efficient welding of advanced ceramics.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 National Natural Science Foundation of China(No.52275301)the Beijing Nova Program(No.20230484311)the Beijing Natural Science Foundation(No.3242002).
文摘Femtosecond laser welding,a novel technique for material joining,faces challenges such as stringent pre-welding requirements and low joint strength when directly welding ceramics.In this study,we addressed the issues associated with the direct welding of yttria-stabilized zirconia(YSZ)and sapphire by first depositing a nanometer-thick Ti layer on the ceramic surface,followed by femtosecond laser welding.Notably,we observed for the first time that femtosecond laser pulses induced the formation of a honeycomb structure at the interface,forming a YSZ/sapphire micro-welding joint characterized by a continuous structure,a honeycomb structure,and Ti-rich phases.This specific joint distribution significantly enhanced the interface transition and improved the joint strength.Under conditions of 8 W laser power,scanning speed of 50 mm/s,and pulse frequency of 200 kHz,the micro-welding joint exhibited optimal interface performance,achieving a maximum shear strength of approximately 79 MPa.Through calculations of the temperature distribution of the interface and the surface energy of the crystal,we conclude that the honeycomb structure arises from the Ti layer,the temperature gradient distribution,and the tendency of sapphire to melt along directions with lower surface energy.The honeycomb structure effectively enriched the transition between the micro-welding interface and the substrate.The new findings of this study offer valuable insights and potential pathways for the reliable and efficient welding of advanced ceramics.
