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Title: Microstructural characterisation of friction stir welding joints of mild steel to Ni-based alloy 625

Abstract

In this study, 6-mm-thick mild steel and Ni-based alloy 625 plates were friction stir welded using a tool rotational speed of 300 rpm and a travel speed of 100 mm·min{sup −1}. A microstructural characterisation of the dissimilar butt joint was performed using optical microscopy, scanning and transmission electron microscopy, and energy dispersive X-ray spectroscopy (XEDS). Six different weld zones were found. In the steel, the heat-affected zone (HAZ) was divided into three zones and was composed of ferrite, pearlite colonies with different morphologies, degenerated regions of pearlite and allotriomorphic and Widmanstätten ferrite. The stir zone (SZ) of the steel showed a coarse microstructure consisting of allotriomorphic and Widmanstätten ferrite, degenerate pearlite and MA constituents. In the Ni-based alloy 625, the thermo-mechanically affected zone (TMAZ) showed deformed grains and redistribution of precipitates. In the SZ, the high deformation and temperature produced a recrystallised microstructure, as well as fracture and redistribution of MC precipitates. The M{sub 23}C{sub 6} precipitates, present in the base material, were also redistributed in the stir zone of the Ni-based alloy. TMAZ in the steel and HAZ in the Ni-based alloy could not be identified. The main restorative mechanisms were discontinuous dynamic recrystallisation in the steel, and discontinuousmore » and continuous dynamic recrystallisation in the Ni-based alloy. The interface region between the steel and the Ni-based alloy showed a fcc microstructure with NbC carbides and an average length of 2.0 μm. - Highlights: • Comprehensive microstructural characterisation of dissimilar joints of mild steel to Ni-based alloy • Friction stir welding of joints of mild steel to Ni-based alloy 625 produces sound welds. • The interface region showed deformed and recrystallised fcc grains with NbC carbides and a length of 2.0 μm.« less

Authors:
 [1]
  1. Brazilian Nanotechnology National Laboratory (LNNano), P.O. Box 6192, Campinas, SP (Brazil)
Publication Date:
OSTI Identifier:
22587064
Resource Type:
Journal Article
Journal Name:
Materials Characterization
Additional Journal Information:
Journal Volume: 110; Other Information: Copyright (c) 2015 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; 77 NANOSCIENCE AND NANOTECHNOLOGY; FCC LATTICES; FERRITE; FERRITES; HEAT AFFECTED ZONE; MICROSTRUCTURE; NIOBIUM CARBIDES; OPTICAL MICROSCOPY; PRECIPITATION; STEELS; WELDED JOINTS; WELDING; X-RAY SPECTROSCOPY

Citation Formats

Rodriguez, J., University of Campinas, Ramirez, A.J., E-mail: ramirezlondono.1@osu.edu, University of Campinas, and Department of Materials Science and Engineering, The Ohio State University — OSU, Columbus, OH 43221. Microstructural characterisation of friction stir welding joints of mild steel to Ni-based alloy 625. United States: N. p., 2015. Web. doi:10.1016/J.MATCHAR.2015.10.023.
Rodriguez, J., University of Campinas, Ramirez, A.J., E-mail: ramirezlondono.1@osu.edu, University of Campinas, & Department of Materials Science and Engineering, The Ohio State University — OSU, Columbus, OH 43221. Microstructural characterisation of friction stir welding joints of mild steel to Ni-based alloy 625. United States. doi:10.1016/J.MATCHAR.2015.10.023.
Rodriguez, J., University of Campinas, Ramirez, A.J., E-mail: ramirezlondono.1@osu.edu, University of Campinas, and Department of Materials Science and Engineering, The Ohio State University — OSU, Columbus, OH 43221. Tue . "Microstructural characterisation of friction stir welding joints of mild steel to Ni-based alloy 625". United States. doi:10.1016/J.MATCHAR.2015.10.023.
@article{osti_22587064,
title = {Microstructural characterisation of friction stir welding joints of mild steel to Ni-based alloy 625},
author = {Rodriguez, J. and University of Campinas and Ramirez, A.J., E-mail: ramirezlondono.1@osu.edu and University of Campinas and Department of Materials Science and Engineering, The Ohio State University — OSU, Columbus, OH 43221},
abstractNote = {In this study, 6-mm-thick mild steel and Ni-based alloy 625 plates were friction stir welded using a tool rotational speed of 300 rpm and a travel speed of 100 mm·min{sup −1}. A microstructural characterisation of the dissimilar butt joint was performed using optical microscopy, scanning and transmission electron microscopy, and energy dispersive X-ray spectroscopy (XEDS). Six different weld zones were found. In the steel, the heat-affected zone (HAZ) was divided into three zones and was composed of ferrite, pearlite colonies with different morphologies, degenerated regions of pearlite and allotriomorphic and Widmanstätten ferrite. The stir zone (SZ) of the steel showed a coarse microstructure consisting of allotriomorphic and Widmanstätten ferrite, degenerate pearlite and MA constituents. In the Ni-based alloy 625, the thermo-mechanically affected zone (TMAZ) showed deformed grains and redistribution of precipitates. In the SZ, the high deformation and temperature produced a recrystallised microstructure, as well as fracture and redistribution of MC precipitates. The M{sub 23}C{sub 6} precipitates, present in the base material, were also redistributed in the stir zone of the Ni-based alloy. TMAZ in the steel and HAZ in the Ni-based alloy could not be identified. The main restorative mechanisms were discontinuous dynamic recrystallisation in the steel, and discontinuous and continuous dynamic recrystallisation in the Ni-based alloy. The interface region between the steel and the Ni-based alloy showed a fcc microstructure with NbC carbides and an average length of 2.0 μm. - Highlights: • Comprehensive microstructural characterisation of dissimilar joints of mild steel to Ni-based alloy • Friction stir welding of joints of mild steel to Ni-based alloy 625 produces sound welds. • The interface region showed deformed and recrystallised fcc grains with NbC carbides and a length of 2.0 μm.},
doi = {10.1016/J.MATCHAR.2015.10.023},
journal = {Materials Characterization},
issn = {1044-5803},
number = ,
volume = 110,
place = {United States},
year = {2015},
month = {12}
}