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
The effects of various hot deformation states on the evolution of microstructures and mechanical properties in diffusion bonded TC4 alloys were investigated using the hot bending of thick plates.Finite element simulat...The effects of various hot deformation states on the evolution of microstructures and mechanical properties in diffusion bonded TC4 alloys were investigated using the hot bending of thick plates.Finite element simulations were conducted to characterize the deformation states during bending at 750℃ with angles of 17°and 32°.The microstructures and mechanical properties of the bonding interface were then analyzed.The joint subjected to uniaxial stress exhibited the highest ultimate tensile strength,which was attributed to the significant accumulation of dislocation density and the low-angle grain boundaries within the grains.The texture strengthening in the basal{0001}plane was also observed,along with a relatively low Schmid factor corresponding to the primary slip systems aligned with the deformation direction.In contrast,the joint under stress-free conditions showed a slip direction that was less favorable for deformation,resulting in an ultimate tensile strength higher than that of the joint under biaxial stress conditions.展开更多
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.
基金the financial support from Fundamental Research Funds for the Central Universities,China(No.YWF-23-L-1012)the National Natural Science Foundation of China(No.52005020).
文摘The effects of various hot deformation states on the evolution of microstructures and mechanical properties in diffusion bonded TC4 alloys were investigated using the hot bending of thick plates.Finite element simulations were conducted to characterize the deformation states during bending at 750℃ with angles of 17°and 32°.The microstructures and mechanical properties of the bonding interface were then analyzed.The joint subjected to uniaxial stress exhibited the highest ultimate tensile strength,which was attributed to the significant accumulation of dislocation density and the low-angle grain boundaries within the grains.The texture strengthening in the basal{0001}plane was also observed,along with a relatively low Schmid factor corresponding to the primary slip systems aligned with the deformation direction.In contrast,the joint under stress-free conditions showed a slip direction that was less favorable for deformation,resulting in an ultimate tensile strength higher than that of the joint under biaxial stress conditions.
