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Title: Transient Microstructure Evolutions and Local Properties of Dual-Phase 980 MPa Grade Steel Via Friction Stir Spot Processing

Abstract

Friction stir processing is a novel solid-state process to modify microstructures and their properties by intense, localized plastic deformation. However, little research has been reported for microstructure evolutions of advanced high-strength steels during the process. The present work focuses on the study of transient microstructure changes and local mechanical properties for friction stir spot processed dual-phase (DP) 980 MPa grade steel (DP980) under different peak temperatures. A pinless silicon nitride ceramic tool was used to produce relatively simple material deformation and flow near the tool. Friction stir spot processed steel samples were characterized by optical and electron microscopies. Furthermore, Vickers microhardness and nano-indentation measurements were used to study local mechanical properties for correlation with microstructures. A swallow layer of refined grains (<0.6 µm) was obtained with a low peak temperature (under 400 °C), whereas higher peak temperatures (>Ac1) led to a change in grain size with different microstructures (fine-grained DP or martensite). Electron back-scattered diffraction characterizations revealed a large deformation in the as-received microstructures (mixture of ferrite and tempered martensite) induced by friction stir spot processing, leading to recrystallization and grain refinement around the stirred zone. Also, nano-indentation measurements showed a higher hardness than the hardness of the as-received DP980.more » Friction stir processing with different process conditions effectively changed microstructures and local mechanical properties.« less

Authors:
 [1]; ORCiD logo [2];  [2]; ORCiD logo [2]
  1. JFE Steel Corporation, Chiba (Japan)
  2. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE); JFE Steel Corporation
OSTI Identifier:
1669766
Grant/Contract Number:  
AC05-00OR22725; NFE-17-06928
Resource Type:
Accepted Manuscript
Journal Name:
Materials
Additional Journal Information:
Journal Volume: 13; Journal Issue: 19; Journal ID: ISSN 1996-1944
Publisher:
MDPI
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Friction stir processing; advanced high-strength steel; characterization; microstructures

Citation Formats

Taniguchi, Koichi, Lim, Yong Chae, Flores-Betancourt, Alexis, and Feng, Zhili. Transient Microstructure Evolutions and Local Properties of Dual-Phase 980 MPa Grade Steel Via Friction Stir Spot Processing. United States: N. p., 2020. Web. https://doi.org/10.3390/ma13194406.
Taniguchi, Koichi, Lim, Yong Chae, Flores-Betancourt, Alexis, & Feng, Zhili. Transient Microstructure Evolutions and Local Properties of Dual-Phase 980 MPa Grade Steel Via Friction Stir Spot Processing. United States. https://doi.org/10.3390/ma13194406
Taniguchi, Koichi, Lim, Yong Chae, Flores-Betancourt, Alexis, and Feng, Zhili. Fri . "Transient Microstructure Evolutions and Local Properties of Dual-Phase 980 MPa Grade Steel Via Friction Stir Spot Processing". United States. https://doi.org/10.3390/ma13194406. https://www.osti.gov/servlets/purl/1669766.
@article{osti_1669766,
title = {Transient Microstructure Evolutions and Local Properties of Dual-Phase 980 MPa Grade Steel Via Friction Stir Spot Processing},
author = {Taniguchi, Koichi and Lim, Yong Chae and Flores-Betancourt, Alexis and Feng, Zhili},
abstractNote = {Friction stir processing is a novel solid-state process to modify microstructures and their properties by intense, localized plastic deformation. However, little research has been reported for microstructure evolutions of advanced high-strength steels during the process. The present work focuses on the study of transient microstructure changes and local mechanical properties for friction stir spot processed dual-phase (DP) 980 MPa grade steel (DP980) under different peak temperatures. A pinless silicon nitride ceramic tool was used to produce relatively simple material deformation and flow near the tool. Friction stir spot processed steel samples were characterized by optical and electron microscopies. Furthermore, Vickers microhardness and nano-indentation measurements were used to study local mechanical properties for correlation with microstructures. A swallow layer of refined grains (<0.6 µm) was obtained with a low peak temperature (under 400 °C), whereas higher peak temperatures (>Ac1) led to a change in grain size with different microstructures (fine-grained DP or martensite). Electron back-scattered diffraction characterizations revealed a large deformation in the as-received microstructures (mixture of ferrite and tempered martensite) induced by friction stir spot processing, leading to recrystallization and grain refinement around the stirred zone. Also, nano-indentation measurements showed a higher hardness than the hardness of the as-received DP980. Friction stir processing with different process conditions effectively changed microstructures and local mechanical properties.},
doi = {10.3390/ma13194406},
journal = {Materials},
number = 19,
volume = 13,
place = {United States},
year = {2020},
month = {10}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Figures / Tables:

Figure 1 Figure 1: (a) Optical micrograph image of the base metal (BM) and (b) magnified SEM of the BM, showing mixture of ferrite (α) and martensite island (MI).

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