Characterization of the interfacial-microstructure evolution and void shrinkage of Ti-22Al-25Nb orthorhombic alloy with different surface roughness during diffusion bonding |
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| Affiliation: | 1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical Unersity, Xi''an, Shaanxi, 710072, China;2. National & Local Joint Engineering Research Center for Precision Thermal Forming Technology of Advanced Metal Materials, Northwestern Polytechnical Unersity, Xi''an, Shaanxi, 710072, China;1. National Institute of Technology, Tiruchirappalli, Tamilnadu, India;2. Alagappa Chettiar College of Engineering and Technology, Karaikudi, Tamilnadu, India;3. SRM University, Chennai, Tamilnadu, India;1. Science and Technology on Thermostructural Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an, Shaanxi 710072, PR China;2. Institute of Advanced Structure Technology, Beijing Institute of Technology, Haidian District Beijing, 100081, PR China;1. School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China;2. Beijing Institute of Control Engineering, Beijing 100190, China;3. National Engineering Research Center of Powder Metallurgy of Titanium & Rare Metals, Guangdong Institute of Materials and Processing, Guangzhou 510650, China;4. Beijing Engineering Research Center of Propulsion Technology, Beijing 100190, China;1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi''an, 710072, PR China;2. Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi''an, 710072, PR China |
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| Abstract: | Ti-22Al-25Nb alloy specimens with different surface roughness were joined, through diffusion bonding at 975 °C at 12.5 MPa. The interfacial-microstructure evolution during this process was characterized via scanning electron microscopy combined with electron probe microanalysis and electron backscatter diffraction analysis. Further, the interfacial void-shrinkage mechanism and the quality of the bonded joints were determined through atomic force microscopy, which revealed the three-dimensional morphologies of the surfaces, and shear strength testing of the joints. The results revealed that fine equiaxed α2 grains are precipitated in the bonding interface of specimens with ground surfaces. These interfacial α2 grains were formed via phase transformation and recrystallization processes, which were triggered by asperity deformation at the contact plane and unavoidable oxygen contamination. Two types of fracture occurred during the shear strength tests, where the bonds generated from (i) polished surfaces failed predominantly along the bond line, and (ii) ground surfaces failed predominantly in the base material away from the bond line. This indicated that the mechanism controlling the void-shrinkage process associated with the contact between two rough surfaces during diffusion bonding varied with the surface roughness: the void-shrinkage process of specimens with (i) polished surfaces is controlled by diffusion, and (ii) ground surfaces was controlled by both diffusion and plastic deformation. |
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| Keywords: | Ti2AlNb alloy Diffusion bonding Interfacial microstructure characterization Shear strength Void shrinkage process |
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