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Title: Effects of Retained Austenite Volume Fraction, Morphology, and Carbon Content on Strength and Ductility of Nanostructured TRIP-assisted Steels

Abstract

With a suite of multi-modal and multi-scale characterization techniques, the present study unambiguously proves that a substantially-improved combination of ultrahigh strength and good ductility can be achieved by tailoring the volume fraction, morphology, and carbon content of the retained austenite (RA) in a transformation-induced-plasticity (TRIP) steel with the nominal chemical composition of 0.19C-0.30Si-1.76Mn-1.52Al (weight percent, wt.%). After intercritical annealing and bainitic holding, a combination ultimate tensile strength (UTS) of 1,100 MPa and true strain of 50% has been obtained, as a result of the ultrafine RA lamellae, which are alternately arranged in the bainitic ferrite around junction regions of ferrite grains. For reference, specimens with a blocky RA, prepared without the bainitic holding, yield a low ductility (35%) and a low UTS (800 MPa). The volume fraction, morphology, and carbon content of RA have been characterized using various techniques, including magnetic probing, scanning electron microscopy (SEM), electron-backscatter-diffraction (EBSD), and transmission electron microscopy (TEM). Interrupted tensile tests, mapped using EBSD in conjunction with the kernel average misorientation (KAM) analysis, reveal that the lamellar RA is the governingmicrostructure component responsible for the higher mechanical stability, compared to the blocky one. By coupling these various techniques, we quantitatively demonstrate that in addition tomore » the RA volume fraction, its morphology and carbon content are equally important in optimizing the strength and ductility of TRIP-assisted steels.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1194286
Report Number(s):
PNNL-SA-110616
VT0505000
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Materials Science and Engineering. A. Structural Materials: Properties, Microstructure and Processing, 636:551-564
Additional Journal Information:
Journal Name: Materials Science and Engineering. A. Structural Materials: Properties, Microstructure and Processing, 636:551-564
Country of Publication:
United States
Language:
English

Citation Formats

Shen, Yongfeng, Qiu, LN, Sun, Xin, Zuo, Liang, Liaw, Peter K., and Raabe, Dierk. Effects of Retained Austenite Volume Fraction, Morphology, and Carbon Content on Strength and Ductility of Nanostructured TRIP-assisted Steels. United States: N. p., 2015. Web. doi:10.1016/j.msea.2015.04.030.
Shen, Yongfeng, Qiu, LN, Sun, Xin, Zuo, Liang, Liaw, Peter K., & Raabe, Dierk. Effects of Retained Austenite Volume Fraction, Morphology, and Carbon Content on Strength and Ductility of Nanostructured TRIP-assisted Steels. United States. https://doi.org/10.1016/j.msea.2015.04.030
Shen, Yongfeng, Qiu, LN, Sun, Xin, Zuo, Liang, Liaw, Peter K., and Raabe, Dierk. 2015. "Effects of Retained Austenite Volume Fraction, Morphology, and Carbon Content on Strength and Ductility of Nanostructured TRIP-assisted Steels". United States. https://doi.org/10.1016/j.msea.2015.04.030.
@article{osti_1194286,
title = {Effects of Retained Austenite Volume Fraction, Morphology, and Carbon Content on Strength and Ductility of Nanostructured TRIP-assisted Steels},
author = {Shen, Yongfeng and Qiu, LN and Sun, Xin and Zuo, Liang and Liaw, Peter K. and Raabe, Dierk},
abstractNote = {With a suite of multi-modal and multi-scale characterization techniques, the present study unambiguously proves that a substantially-improved combination of ultrahigh strength and good ductility can be achieved by tailoring the volume fraction, morphology, and carbon content of the retained austenite (RA) in a transformation-induced-plasticity (TRIP) steel with the nominal chemical composition of 0.19C-0.30Si-1.76Mn-1.52Al (weight percent, wt.%). After intercritical annealing and bainitic holding, a combination ultimate tensile strength (UTS) of 1,100 MPa and true strain of 50% has been obtained, as a result of the ultrafine RA lamellae, which are alternately arranged in the bainitic ferrite around junction regions of ferrite grains. For reference, specimens with a blocky RA, prepared without the bainitic holding, yield a low ductility (35%) and a low UTS (800 MPa). The volume fraction, morphology, and carbon content of RA have been characterized using various techniques, including magnetic probing, scanning electron microscopy (SEM), electron-backscatter-diffraction (EBSD), and transmission electron microscopy (TEM). Interrupted tensile tests, mapped using EBSD in conjunction with the kernel average misorientation (KAM) analysis, reveal that the lamellar RA is the governingmicrostructure component responsible for the higher mechanical stability, compared to the blocky one. By coupling these various techniques, we quantitatively demonstrate that in addition to the RA volume fraction, its morphology and carbon content are equally important in optimizing the strength and ductility of TRIP-assisted steels.},
doi = {10.1016/j.msea.2015.04.030},
url = {https://www.osti.gov/biblio/1194286}, journal = {Materials Science and Engineering. A. Structural Materials: Properties, Microstructure and Processing, 636:551-564},
number = ,
volume = ,
place = {United States},
year = {Mon Jun 01 00:00:00 EDT 2015},
month = {Mon Jun 01 00:00:00 EDT 2015}
}