Diffusion bonding is a near net shape forming process that can join dissimilar materials through atomic diffusion under a high pressure at a high temperature.Titanium alloy TC4（Ti-6 Al-4 V）and 4 J29 Kovar alloy（Fe-...Diffusion bonding is a near net shape forming process that can join dissimilar materials through atomic diffusion under a high pressure at a high temperature.Titanium alloy TC4（Ti-6 Al-4 V）and 4 J29 Kovar alloy（Fe-29 Ni-17 Co）were diffusely bonded by a vacuum hot-press sintering process in the temperature range of 700-850°C and bonding time of 120 min,under a pressure of 34.66 MPa.Interfacial microstructures and intermetallic compounds of the diffusion-bonded joints were characterized by optical microscopy,scanning electron microscopy,X-ray diffraction（XRD）and energy dispersive spectroscopy（EDS）.The elemental diffusion across the interface was revealed by electron probe microanalysis.Mechanical properties of joints were investigated by micro Vickers hardness and tensile strength.Results of EDS and XRD indicated that（Fe,Co,Ni）-Ti,TiNi,Ti_2Ni,TiNi_2,Fe_2 Ti,Ti_（17） Mn_3 and Al_6 Ti_（19） were formed at the interface.When the bonding temperature was raised from 700 to 850°C,the voids of interface were reduced and intermetallic layers were widened.Maximum tensile strength of joints at 53.5 MPa was recorded by the sintering process at 850°C for 120 min.Fracture surface of the joint indicated brittle nature,and failure took place through interface of intermetallic compounds.Based on the mechanical properties and microstructure of the diffusion-bonded joints,diffusion mechanisms between Ti-6 Al-4 Vtitanium and Fe-29 Ni-17 Co Kovar alloys were analyzed in terms of elemental diffusion,nucleation and growth of grains,plastic deformation and formation of intermetallic compounds near the interface.展开更多
Micro-structure related behavior of diffusion bonding joints is a crucial issue in device and reactor fabrication of Micro Chemo Mechanical Systems.However,the previous studies have been focused on the macro mechanica...Micro-structure related behavior of diffusion bonding joints is a crucial issue in device and reactor fabrication of Micro Chemo Mechanical Systems.However,the previous studies have been focused on the macro mechanical performance of diffusion bonded joint,especially diffusion bonding conditions effects on tensile strength,shearing strength and fatigue strength.The research of interfacial micro-voids and microstructures evolution for failure mechanism has not been carried out for diffusion-bonded joints.An interfacial electrical resistance measuring method is proposed to evaluate the quality of bonded joints and verified by using two-dimensional finite-element simulation.The influences of micro void geometry on increments of resistance are analyzed and the relationship between bonded area fraction and resistance increment is established by theoretical analysis combined with simulated results.Metallographic inspections and micro-hardness testing are conducted near the interface of diffusion bonded joints.For the purpose of identifying the failure mechanisms of the joints,both microscopic tensile and fatigue tests are conducted on the self-developed in-situ microscopic fatigue testing system.Based on the microscopic observations,the mechanism of interfacial failure is addressed.The observation result shows that for 316LSS diffusion-bonded joints,microstructure evolution and effect of micro-voids play a key role in interfacial failure mechanism.Finally,a new life prediction model in terms of the increment of electrical resistance is developed and confirmed by the experimental results.The proposed study is initiated that constituted a primary interfacial failure mechanism on micron scale and provide the life prediction for reliability of components sealed by diffusion bonding.展开更多
基金supported by National Natural Science Foundation of China(No.51201143)Fundamental Research Funds for the Central Universities (No.2682015CX001)+5 种基金China Postdoctoral Science Foundation(No.2015M570794)Key Laboratory of Infrared Imaging Materials and Detectors,Shanghai Institute of Technical Physics,Chinese Academy of Sciences(No.IIMDKFJJ-14-04)Sichuan Science and Technology Support Program(No.2016FZ0079)R&D Projects Funding from the Research Council of Norway(No.263875/H30)supported by the U.S. National Science Foundation No.1436120supported by DoD W911NF14-1-0060
文摘Diffusion bonding is a near net shape forming process that can join dissimilar materials through atomic diffusion under a high pressure at a high temperature.Titanium alloy TC4（Ti-6 Al-4 V）and 4 J29 Kovar alloy（Fe-29 Ni-17 Co）were diffusely bonded by a vacuum hot-press sintering process in the temperature range of 700-850°C and bonding time of 120 min,under a pressure of 34.66 MPa.Interfacial microstructures and intermetallic compounds of the diffusion-bonded joints were characterized by optical microscopy,scanning electron microscopy,X-ray diffraction（XRD）and energy dispersive spectroscopy（EDS）.The elemental diffusion across the interface was revealed by electron probe microanalysis.Mechanical properties of joints were investigated by micro Vickers hardness and tensile strength.Results of EDS and XRD indicated that（Fe,Co,Ni）-Ti,TiNi,Ti_2Ni,TiNi_2,Fe_2 Ti,Ti_（17） Mn_3 and Al_6 Ti_（19） were formed at the interface.When the bonding temperature was raised from 700 to 850°C,the voids of interface were reduced and intermetallic layers were widened.Maximum tensile strength of joints at 53.5 MPa was recorded by the sintering process at 850°C for 120 min.Fracture surface of the joint indicated brittle nature,and failure took place through interface of intermetallic compounds.Based on the mechanical properties and microstructure of the diffusion-bonded joints,diffusion mechanisms between Ti-6 Al-4 Vtitanium and Fe-29 Ni-17 Co Kovar alloys were analyzed in terms of elemental diffusion,nucleation and growth of grains,plastic deformation and formation of intermetallic compounds near the interface.
基金supported by National Natural Science Foundation of China(Grant No.50475068)
文摘Micro-structure related behavior of diffusion bonding joints is a crucial issue in device and reactor fabrication of Micro Chemo Mechanical Systems.However,the previous studies have been focused on the macro mechanical performance of diffusion bonded joint,especially diffusion bonding conditions effects on tensile strength,shearing strength and fatigue strength.The research of interfacial micro-voids and microstructures evolution for failure mechanism has not been carried out for diffusion-bonded joints.An interfacial electrical resistance measuring method is proposed to evaluate the quality of bonded joints and verified by using two-dimensional finite-element simulation.The influences of micro void geometry on increments of resistance are analyzed and the relationship between bonded area fraction and resistance increment is established by theoretical analysis combined with simulated results.Metallographic inspections and micro-hardness testing are conducted near the interface of diffusion bonded joints.For the purpose of identifying the failure mechanisms of the joints,both microscopic tensile and fatigue tests are conducted on the self-developed in-situ microscopic fatigue testing system.Based on the microscopic observations,the mechanism of interfacial failure is addressed.The observation result shows that for 316LSS diffusion-bonded joints,microstructure evolution and effect of micro-voids play a key role in interfacial failure mechanism.Finally,a new life prediction model in terms of the increment of electrical resistance is developed and confirmed by the experimental results.The proposed study is initiated that constituted a primary interfacial failure mechanism on micron scale and provide the life prediction for reliability of components sealed by diffusion bonding.
