Material Interactions in a Novel Pinless Tool Approach to Friction Stir Spot Welding Thin Aluminum Sheet

The requirement for a probe, or pin, in friction stir spot welding (FSSW) leads to an undesirable keyhole and “hooking,” which can influence the fracture path and weld strength. Furthermore, the full weld cycle for FSSW is typically longer than ideal for the automotive industry, being 2 to 5 seconds...

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Bibliographic Details
Published inMetallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 42; no. 5; pp. 1266 - 1282
Main Authors Bakavos, Dimitrios, Chen, Yingchun, Babout, Laurent, Prangnell, Phil
Format Journal Article
LanguageEnglish
Published Boston Springer US 01.05.2011
Springer Nature B.V
Subjects
Aluminum
Automobile industry
Bond strength
Characterization and Evaluation of Materials
Chemistry and Materials Science
Cost control
Materials Science
Metallic Materials
Nanotechnology
Shear strength
Shear tests
Structural Materials
Surfaces and Interfaces
Thin Films
Welding
Weld Interface
Weld Line
Friction Stir Spot Welding
Weld Zone
Weld Time
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Summary:The requirement for a probe, or pin, in friction stir spot welding (FSSW) leads to an undesirable keyhole and “hooking,” which can influence the fracture path and weld strength. Furthermore, the full weld cycle for FSSW is typically longer than ideal for the automotive industry, being 2 to 5 seconds. Here, it is shown that using a novel pinless tool design it is possible to achieve high lap shear strength (~3.4 kN) in thin aluminum sheet (~1 mm thick), with short weld cycle times (<1 second). Several techniques have been exploited to study the material flow and mechanisms of weld formation in pinless FSSW, including high-resolution X-ray tomography, to understand the role of the tool design and weld parameters. Despite the “simple” nature of a pinless tool, material flow in the weld zone was found to be surprisingly complex and strongly influenced by surface features on the tool, which greatly increased the penetration of the plastic zone into the bottom sheet. Because of the rapid thermal cycle and high level of grain refinement, the weld zone was found to develop a higher strength than the parent material with little evidence of a heat affected zone (HAZ) after postweld natural aging.
ISSN:1073-5623
1543-1940
DOI:10.1007/s11661-010-0514-x