Wetting behavior and bonding characteristics of bismuth-based glass brazes used to join Li-Ti ferrite systems |
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| Affiliation: | 1. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China;2. Department of Mechanical Engineering, College of Engineering, University of Kentucky, Lexington, KY 40506, USA;1. Department of Materials & Metallurgical Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh;2. School of Materials Science & Engineering, Nanyang Technological University, Singapore 639798, Singapore;1. Key Laboratory of Inorganic Functional Material and Device, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. Department of materials, Chongqing University of Technology, Chongqing 400050, China;1. School of Materials Science and Engineering, Chang''an University, Xi''an, 710064, Shaanxi, PR China;2. Science and Technology on Thermostructural Composite Materials Laboratory, Northwestern Polytechnical University, Xi''an, 710072, Shaanxi, PR China |
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| Abstract: | A series of bismuth-based glass brazes were used to join Li-Ti ferrite. The wetting behavior and bonding characteristics of glass brazes utilized to join Li-Ti ferrite were systematically investigated. The glass brazes feature a good CTEs match, and a favorable wetting ability over Li-Ti ferrite mating surfaces. Upon brazing, the Bi-rich phases (Bi46Fe2O72, Bi12SiO2 and Bi24B2O39) and Zn-rich phase (ZnO) were observed in the Li-Ti ferrite/Bi40 and Li-Ti ferrite/Bi35 joints. The Zn2SiO4, ZnFe2O4 and Bi5Ti3FeO15 whiskers were detected in the Li-Ti ferrite/Bi25, Li-Ti ferrite/Bi20 and Li-Ti ferrite/Bi25-BC joints, respectively. No crystalline phase was detected in the Li-Ti ferrite/Bi30-BF joint. Multiple factors impact the joint strength, such as the three-point bending strength of glass brazes, the CTE match of the glass braze and the Li-Ti ferrite, as well as the crystal phases within the seam. The joint strength has the maximum value of 86 MPa for a Li-Ti ferrite/Bi25-Ba couples. The main impact is attributed to the strengthening effect of Bi5Ti3FeO15 whiskers. The dielectric properties of Li-Ti ferrite/glass braze joints show a stronger frequency dependence than that of Li-Ti ferrite at low frequency. This is attributed to the formation of new interfaces. The glass matrix or a crystal phase with a higher dielectric constant could counteract the decrease in the dielectric constant of heat-treated Li-Ti ferrite. Therefore, the dielectric constant of joint, especially that of Li-Ti ferrite/Bi25-BC joint, would be near that of the original Li-Ti ferrite at a high frequency. Meanwhile, no increase in the dielectric loss tangent of a joint takes place. |
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| Keywords: | Li-Ti ferrite Bismuth-based glass Wetting ability Microstructure Joint strength Dielectric constant Dielectric loss tangent |
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