Interfacial bonding mechanism in Al/coated steel dissimilar refill friction stir spot welds |
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| Affiliation: | 1. State Key Laboratory of Solidification Processing, Shaanxi Key Laboratory of Friction Welding Technologies, Northwesltern Polytechnical University, Xi''an 710072, Shaanxi, PR China;2. Mechanical Engineering Department, TEI of Crete, Heraklion, Crete 71004, Greece;3. Beijing Aeronautical Manufacturing Technology Research Institute, Beijing 100024, PR China;1. Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240, P.R. China;2. The State Key Lab of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, P.R. China;3. Beijing FSW Technology Co., Ltd, Beijing 101107, P.R. China |
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| Abstract: | Defect-free dissimilar Al/zinc coated steel and Al/AlSi coated steel welds were successfully fabricated by refill friction stir spot welding. However, Al alloy and uncoated steel could not be welded under the same welding condition. Al-Zn eutectic layer formed at the Al/zinc coated steel interface showed non-uniformity in thickness and nanoscale intermetallic (IMC) produced was discontinuous. The bonding formation between the Al-Zn layer and the surrounding materials was attributed to a liquid/solid reaction mechanism. Bonding formation at Al alloy and AlSi coated steel interface was attributed to a solid/solid reaction mechanism, as the joining process did not involve with melting of base metals or AlSi coating materials. Kissing bond formed at the weld boundary acted as a crack initiation and propagation site, and the present study showed that weld strength of Al 5754/AlSi coated steel was greatly influenced by properties of original IMC layer. |
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| Keywords: | Refill friction stir spot welding Al alloy Steel Coated materials Joining mechanism |
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