NDLI: Study of Embrittled Friction-Stir-Welds

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Muhammad, A. Wahab Taylor, David Meletis, Efstathios
Copyright Year	2009
Abstract	A reduction in mechanical properties has been observed in Friction-Stir-Welded (FSW) Aluminum panels. This reduction in strength has generally been attributed to Residual Oxide Defect (ROD). From NASA experience it was also found that certain processing parameters would yield these reduced mechanical properties. The strength of FSW Aluminum panels generally decreases with increasing tool travel rate, decreasing rotation speed, and offset of the weld seam to the retreating side of the FSW tool. The microstructure of welds exhibiting these strength reduction as well as welds that behaved as expected were examined to determine microstructural effects of processing parameters. Therefore the evolutions of microstructural properties are immensely important to understand and evaluate to avoid any catastrophic failures due to the defects arising from welding operations. Scanning Electron Microscopy shows that these weld conditions are accompanied by large precipitates along the grain boundary for both AA-2219 and AA-2195 FSW welded samples. Transmission Electron Microscopy (TEM) also shows the precipitates to be “theta particles (Al2Cu)” and intermetallics in the AA-2219; and T1 (Al2CuLi), and TB particles in the AA-2195. The large size and heavy distributions of these precipitates, especially on the advancing side of the weld seam may influence these properties. It is determined that the existence of ROD in the samples must be analyzed systematically and carefully through the evolutions of microstructures, if catastrophic failures are to be avoided during service conditions. A more complete understanding of this phenomenon is necessary to ensure consistent and predictable weld properties thereby reducing or eliminating the risk of unforeseen failures.
Starting Page	161
Ending Page	167
Page Count	7
File Format	PDF
ISBN	9780791843871
DOI	10.1115/IMECE2009-13086
e-ISBN	9780791838631
Volume Number	Volume 14: Processing and Engineering Applications of Novel Materials
Conference Proceedings	ASME 2009 International Mechanical Engineering Congress and Exposition
Language	English
Publisher Date	2009-11-13
Publisher Place	Lake Buena Vista, Florida, USA
Access Restriction	Subscribed
Subject Keyword	Friction-stir-welding (fsw) Microstructural evolution Residual oxide defect Aluminum alloys aa-2219 and aa-2195 Precipitates Friction Welding Welded joints
Content Type	Text
Resource Type	Article

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