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Title: Focused Acoustic Beam Evaluation of Aluminum - Lithium Friction Stir Weld

Abstract

Local elastic variations were measured across a friction stir welded zone in Al-Li alloy with the use of a focused acoustic beam. The near surface microstructure was investigated by measuring both the amplitude and the local velocity of the Rayleigh Surface Waves (RSW). Both the amplitude and velocity of the focused longitudinal acoustic waves propagating through the thickness of the sample has been used for examination of the variations in the localized bulk elastic properties. The variations observed across the weld zone are explained based on microstructure and residual stress variations.

Authors:
; ;  [1];  [2]
  1. University of Dayton Research Institute, 300 College Park, Dayton, OH 45469-0127 (United States)
  2. Air Force Research Laboratory, Metals, Ceramics and NDE Division, 2230 Tenth St., Wright Patterson AFB, Dayton, OH 45433-7817 (United States)
Publication Date:
OSTI Identifier:
21054928
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 894; Journal Issue: 1; Conference: Conference on review of progress in quantitative nondestructive evaluation, Portland, OR (United States), 30 Jul - 4 Aug 2006; Other Information: DOI: 10.1063/1.2718089; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM; AMPLITUDES; ELASTICITY; EVALUATION; FRICTION; INTERMETALLIC COMPOUNDS; LITHIUM; MICROSTRUCTURE; RAYLEIGH WAVES; RESIDUAL STRESSES; SOUND WAVES; SURFACES; THICKNESS; VARIATIONS; WAVE PROPAGATION; WELDED JOINTS

Citation Formats

Sathish, Shamachary, Martin, Richard W., Reibel, Richard, and Jata, Kumar V. Focused Acoustic Beam Evaluation of Aluminum - Lithium Friction Stir Weld. United States: N. p., 2007. Web. doi:10.1063/1.2718089.
Sathish, Shamachary, Martin, Richard W., Reibel, Richard, & Jata, Kumar V. Focused Acoustic Beam Evaluation of Aluminum - Lithium Friction Stir Weld. United States. doi:10.1063/1.2718089.
Sathish, Shamachary, Martin, Richard W., Reibel, Richard, and Jata, Kumar V. Wed . "Focused Acoustic Beam Evaluation of Aluminum - Lithium Friction Stir Weld". United States. doi:10.1063/1.2718089.
@article{osti_21054928,
title = {Focused Acoustic Beam Evaluation of Aluminum - Lithium Friction Stir Weld},
author = {Sathish, Shamachary and Martin, Richard W. and Reibel, Richard and Jata, Kumar V.},
abstractNote = {Local elastic variations were measured across a friction stir welded zone in Al-Li alloy with the use of a focused acoustic beam. The near surface microstructure was investigated by measuring both the amplitude and the local velocity of the Rayleigh Surface Waves (RSW). Both the amplitude and velocity of the focused longitudinal acoustic waves propagating through the thickness of the sample has been used for examination of the variations in the localized bulk elastic properties. The variations observed across the weld zone are explained based on microstructure and residual stress variations.},
doi = {10.1063/1.2718089},
journal = {AIP Conference Proceedings},
number = 1,
volume = 894,
place = {United States},
year = {Wed Mar 21 00:00:00 EDT 2007},
month = {Wed Mar 21 00:00:00 EDT 2007}
}
  • The precipitation sequence in friction stir weld of 6063 aluminum during postweld aging, associated with Vickers hardness profiles, has been examined by transmission electron microscopy. Friction stir welding produces a softened region in the weld, which is characterized by dissolution and growth of the precipitates. The precipitate-dissolved region contains a minimum hardness region in the as-welded condition. In the precipitate-dissolved region , postweld aging markedly increases the density of strengthening precipitates and leads to a large increase in hardness. On the other hand, aging forms few new precipitates in the precipitate-coarsened region, which shows a slight increase in hardness. Themore » postweld aging at 443 K for 43.2 ks (12 hours) gives greater hardness in the overall weld than in the as-received base material and shifts the minimum hardness from the as-welded minimum hardness region t the precipitate-coarsened region. These hardness changes are consistent with the subsequent precipitation behavior during postweld aging. The postweld solution heat treatment (SHT) and aging achieve a high density of strengthening precipitates and bring a high hardness homogeneously in the overall weld.« less
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  • Tool wear for threaded steel pin tools declines with decreasing rotation speed and increasing traverse or weld speeds for the friction-stir welding (FSW) of Al 359+20% SiC metal-matrix composite (MMC). Less than 10% tool wear occurs when the threaded tool erodes to a self-optimized shape resembling a pseudo-hour glass at weld traverse distances in excess of 3 m. There is only a 7% reduction in the SiC mean particle size in the weld zone for self-optimized pin tools with no threads as compared with a 25% variation for threaded tools wearing significantly at the start of welding. The weld zonemore » becomes more homogeneous for efficient welding with self-optimized tools, and there is a reduction in the weld zone grain size due to dynamic recrystallization, which facilitates the solid-state flow. Transmission electron microscopy shows little difference in the dislocation density from the base material to the weld zone, but there is a propensity of dislocation loops in the weld zone. The weld zone is observed to harden by as much as 30%, in contrast to the base material, as a consequence of the recrystallized grain size reduction and the SiC particles distributed therein.« less
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