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Title: Formation mechanisms of periodic longitudinal microstructure and texture patterns in friction stir welded magnesium AZ80

Abstract

Many studies of friction stir welding have shown that periodicity of metal flow around the tool pin may result in the formation of periodic differences in microstructure and texture in the weld nugget area correlated with the weld pitch. The current work investigates the periodicity of magnesium weld microtexture in the nugget region and its association with material flow using optical and electron microscopy. Two welds created in AZ80 at different processing conditions are presented in detail, one illustrating periodic longitudinal texture change, and one showing for the first time that periodic variations in texture, grain size, or composition are not defining features of periodic nugget flow. While nugget texture is dominated by shear deformation, it was found here to be affected to a lesser degree by compaction of material behind the welding tool, which led to reduction in intensity of the shear texture fiber. The decreased tendency for magnesium based alloys to form periodic patterns as compared to aluminum based alloys is explained with reference to the shear textures. - Highlights: •It is shown here that periodic material flow in the nugget does not necessitate longitudinal texture patterns. •Longitudinal texture patterns are shown to be present or absent inmore » Mg AZ80 based on processing conditions. •Texture in the nugget is mainly dictated by shear deformation, but has measurable effects from other deformation modes. •Explanation of why longitudinal texture change is frequently reported in aluminum but not magnesium alloys is provided. •A new vector visualization of material flow based on EBSD data analysis is shown.« less

Authors:
 [1]
  1. Depar
Publication Date:
OSTI Identifier:
22689663
Resource Type:
Journal Article
Journal Name:
Materials Characterization
Additional Journal Information:
Journal Volume: 122; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1044-5803
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM BASE ALLOYS; BACKSCATTERING; COMPARATIVE EVALUATIONS; DATA ANALYSIS; DEFECTS; DEFORMATION; ELECTRON DIFFRACTION; ELECTRON MICROSCOPY; FIBERS; FRICTION; GRAIN SIZE; MAGNESIUM; PERIODICITY; SHEAR; TEXTURE; VOIDS; WELDED JOINTS; WELDING

Citation Formats

Hiscocks, J., E-mail: j.hiscocks@queensu.ca. Formation mechanisms of periodic longitudinal microstructure and texture patterns in friction stir welded magnesium AZ80. United States: N. p., 2016. Web. doi:10.1016/J.MATCHAR.2016.10.004.
Hiscocks, J., E-mail: j.hiscocks@queensu.ca. Formation mechanisms of periodic longitudinal microstructure and texture patterns in friction stir welded magnesium AZ80. United States. doi:10.1016/J.MATCHAR.2016.10.004.
Hiscocks, J., E-mail: j.hiscocks@queensu.ca. Thu . "Formation mechanisms of periodic longitudinal microstructure and texture patterns in friction stir welded magnesium AZ80". United States. doi:10.1016/J.MATCHAR.2016.10.004.
@article{osti_22689663,
title = {Formation mechanisms of periodic longitudinal microstructure and texture patterns in friction stir welded magnesium AZ80},
author = {Hiscocks, J., E-mail: j.hiscocks@queensu.ca},
abstractNote = {Many studies of friction stir welding have shown that periodicity of metal flow around the tool pin may result in the formation of periodic differences in microstructure and texture in the weld nugget area correlated with the weld pitch. The current work investigates the periodicity of magnesium weld microtexture in the nugget region and its association with material flow using optical and electron microscopy. Two welds created in AZ80 at different processing conditions are presented in detail, one illustrating periodic longitudinal texture change, and one showing for the first time that periodic variations in texture, grain size, or composition are not defining features of periodic nugget flow. While nugget texture is dominated by shear deformation, it was found here to be affected to a lesser degree by compaction of material behind the welding tool, which led to reduction in intensity of the shear texture fiber. The decreased tendency for magnesium based alloys to form periodic patterns as compared to aluminum based alloys is explained with reference to the shear textures. - Highlights: •It is shown here that periodic material flow in the nugget does not necessitate longitudinal texture patterns. •Longitudinal texture patterns are shown to be present or absent in Mg AZ80 based on processing conditions. •Texture in the nugget is mainly dictated by shear deformation, but has measurable effects from other deformation modes. •Explanation of why longitudinal texture change is frequently reported in aluminum but not magnesium alloys is provided. •A new vector visualization of material flow based on EBSD data analysis is shown.},
doi = {10.1016/J.MATCHAR.2016.10.004},
journal = {Materials Characterization},
issn = {1044-5803},
number = ,
volume = 122,
place = {United States},
year = {2016},
month = {12}
}