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Title: Stability of the grain structure in 2219-O aluminum alloy friction stir welds during solution treatment

Abstract

The stability of the grain structure in 2219-O aluminum alloy friction stir welds during solution treatment has been investigated. Experimental results show that the solution treatment causes drastic grain growth, Grain growth initiates at the surface and the bottom of the weld and then extends to the weld centre within several minutes. The solution treatment temperature and the welding heat input have a significant effect on grain growth. The higher the solution temperature, or the higher the welding heat input, the greater the grain growth. The instability of the grains is attributed to an imbalance between thermodynamic driving forces for grain growth and the pinning forces impeding grain boundary migration during solution treatment.

Authors:
 [1];  [2];  [2]
  1. National Key Laboratory of Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001 (China) and National Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001 (China). E-mail: armstrong@hit.edu.cn
  2. National Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001 (China)
Publication Date:
OSTI Identifier:
21003531
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 58; Journal Issue: 2; Other Information: DOI: 10.1016/j.matchar.2006.04.015; PII: S1044-5803(06)00114-8; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM ALLOYS; FRICTION; GRAIN BOUNDARIES; GRAIN GROWTH; HEAT; INSTABILITY; MAGNETIC FLUX; STABILITY; WELDED JOINTS; WELDING

Citation Formats

Chen, Y.C., Feng, J.C., and Liu, H.J. Stability of the grain structure in 2219-O aluminum alloy friction stir welds during solution treatment. United States: N. p., 2007. Web. doi:10.1016/j.matchar.2006.04.015.
Chen, Y.C., Feng, J.C., & Liu, H.J. Stability of the grain structure in 2219-O aluminum alloy friction stir welds during solution treatment. United States. doi:10.1016/j.matchar.2006.04.015.
Chen, Y.C., Feng, J.C., and Liu, H.J. Thu . "Stability of the grain structure in 2219-O aluminum alloy friction stir welds during solution treatment". United States. doi:10.1016/j.matchar.2006.04.015.
@article{osti_21003531,
title = {Stability of the grain structure in 2219-O aluminum alloy friction stir welds during solution treatment},
author = {Chen, Y.C. and Feng, J.C. and Liu, H.J.},
abstractNote = {The stability of the grain structure in 2219-O aluminum alloy friction stir welds during solution treatment has been investigated. Experimental results show that the solution treatment causes drastic grain growth, Grain growth initiates at the surface and the bottom of the weld and then extends to the weld centre within several minutes. The solution treatment temperature and the welding heat input have a significant effect on grain growth. The higher the solution temperature, or the higher the welding heat input, the greater the grain growth. The instability of the grains is attributed to an imbalance between thermodynamic driving forces for grain growth and the pinning forces impeding grain boundary migration during solution treatment.},
doi = {10.1016/j.matchar.2006.04.015},
journal = {Materials Characterization},
number = 2,
volume = 58,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}
  • Aluminum alloy 2219-T6 was friction stir processed using a novel submerged processing technique to facilitate cooling. Processing was conducted at a constant tool traverse speed of 200 mm/min and spindle rotation speeds in the range from 600 to 800 rpm. The microstructural characteristics of the base metal and processed zone, including grain structure and precipitation behavior, were studied using optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Microhardness maps were constructed on polished cross sections of as-processed samples. The effect of tool rotation speed on the microstructure and hardness of the stir zone was investigated. Themore » average grain size of the stir zone was much smaller than that of the base metal, but the hardness was also lower due to the formation of equilibrium θ precipitates from the base metal θ′ precipitates. Stir zone hardness was found to decrease with increasing rotation speed (heat input). The effect of processing conditions on strength (hardness) was rationalized based on the competition between grain refinement strengthening and softening due to precipitate overaging. - Highlights: • SZ grain size (∼ 1 μm) is reduced by over one order of magnitude relative to the BM. • Hardness in the SZ is lower than that of the precipitation strengthened BM. • Metastable θ′ in the base metal transforms to equilibrium θ in the stir zone. • Softening in the SZ results from a decrease of precipitation strengthening.« less
  • The dislocation density and grain structure of a friction stir welded 6061-T6 aluminum alloy was determined as a function of distance from the weld centerline using high-resolution micro-beam x-ray diffraction. The results of the x-ray peak profile analysis show that the dislocation density is about 1.2 x 10^14 m-2 inside and 4.8 x 10^14 m-2 outside of the weld region. The average subgrain size is about 180 nm in both regions. Compared to the base material, the dislocation density was significantly decreased in the dynamic recrystallized zone of the friction stir welds, which is a good correlation with the TEMmore » observations. The influence of the dislocation density on the strain hardening behavior during tensile deformation is also discussed.« less
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