The origin of the onion ring structure is an important issue in friction stir welding process but has not been firmly established yet. This paper peresents optical macro- and micrographs of friction stir welds on a copper alloy produced by a non-threaded tool pin. It is shown that onion ring structure can be created by non-threaded tool pin in transverse cross-section of friction stir weld of copper plate. The macrographs of transverse cross-sections exhibit contrasting bands. A microstructural study shows that the weld has lamellar structure, and the bands are sections of weld layers.
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2.
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3.
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4.
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5.
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KrishnanK. N.: ‘On the formation of onion rings in friction stir welds’, Mater. Sci. Eng. A, 2002, A327, 246–251.
7.
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8.
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AttallahM. M., DavisC. L. and Strang WoodM.: ‘Influence of base metal microstructure on microstructural development in aluminium based alloy friction stir welds’, Sci. Technol. Weld. Join., 2007, 12, 361–369.
10.
XieG. M., MaZ. Y. and GengL.: ‘Development of a fine-grained microstructure and the properties of a nugget zone in friction stir welded pure copper’, J. Scr. Mater., 2007, 57, 73–76.
11.
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CuiG. R., MaZ. Y. and LiS. X.: ‘Periodical plastic flow pattern in friction stir processed Al–Mg alloy’, J. Scr. Mater., 2008, 58, 1082–1085.
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