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Title: Influence of Various Material Design Parameters on Deformation Behaviors of TRIP Steels

Abstract

In this paper, the microstructure-based finite element modeling method is used as a virtual design tool in investigating the respective influence of various material design parameters on the deformation behaviors of transformation induced plasticity (TRIP) steels. For this purpose, the separate effects of several different material design parameters, such as the volume fraction and stability of austenite phase and the strengths of the constituent phases, on the ultimate tensile strength (UTS) and ductility/formability of TRIP steels are quantitatively examined using different representative volume elements (RVEs) representing different TRIP steels. The computational results suggest that higher austenite stability is helpful in enhancing the ductility and formability of TRIP steels by delaying the martensitic transformation to a later stage, whereas increase of austenite volume fraction and/or ferrite strength alone is not beneficial to improve the performance of TRIP steels. The results in this study also indicate that various material design parameters must be adjusted concurrently to develop high performance TRIP steels. For example, the austenite strength should increase over the ferrite strength in order to induce the gradual/smooth martensitic transformation, and the strength disparity between the ferrite and the freshly-formed martensite phases should decrease in order to avoid higher stress/strain concentration alongmore » the phase boundaries. The modeling approach and results presented in this paper can be helpful in providing the deformation fundamentals for the development of high performance TRIP steels.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1222175
Report Number(s):
PNNL-SA-72448
VT0505000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Computational Materials Science, 50(2):720-730
Country of Publication:
United States
Language:
English
Subject:
TRIP steels; Austenite stability; Austenite volume fraction; Microstructure; Finite element analysis; Material design parameters

Citation Formats

Choi, Kyoo Sil, Soulami, Ayoub, Liu, Wenning N., Sun, Xin, and Khaleel, Mohammad A. Influence of Various Material Design Parameters on Deformation Behaviors of TRIP Steels. United States: N. p., 2010. Web. doi:10.1016/j.commatsci.2010.10.002.
Choi, Kyoo Sil, Soulami, Ayoub, Liu, Wenning N., Sun, Xin, & Khaleel, Mohammad A. Influence of Various Material Design Parameters on Deformation Behaviors of TRIP Steels. United States. doi:10.1016/j.commatsci.2010.10.002.
Choi, Kyoo Sil, Soulami, Ayoub, Liu, Wenning N., Sun, Xin, and Khaleel, Mohammad A. 2010. "Influence of Various Material Design Parameters on Deformation Behaviors of TRIP Steels". United States. doi:10.1016/j.commatsci.2010.10.002.
@article{osti_1222175,
title = {Influence of Various Material Design Parameters on Deformation Behaviors of TRIP Steels},
author = {Choi, Kyoo Sil and Soulami, Ayoub and Liu, Wenning N. and Sun, Xin and Khaleel, Mohammad A.},
abstractNote = {In this paper, the microstructure-based finite element modeling method is used as a virtual design tool in investigating the respective influence of various material design parameters on the deformation behaviors of transformation induced plasticity (TRIP) steels. For this purpose, the separate effects of several different material design parameters, such as the volume fraction and stability of austenite phase and the strengths of the constituent phases, on the ultimate tensile strength (UTS) and ductility/formability of TRIP steels are quantitatively examined using different representative volume elements (RVEs) representing different TRIP steels. The computational results suggest that higher austenite stability is helpful in enhancing the ductility and formability of TRIP steels by delaying the martensitic transformation to a later stage, whereas increase of austenite volume fraction and/or ferrite strength alone is not beneficial to improve the performance of TRIP steels. The results in this study also indicate that various material design parameters must be adjusted concurrently to develop high performance TRIP steels. For example, the austenite strength should increase over the ferrite strength in order to induce the gradual/smooth martensitic transformation, and the strength disparity between the ferrite and the freshly-formed martensite phases should decrease in order to avoid higher stress/strain concentration along the phase boundaries. The modeling approach and results presented in this paper can be helpful in providing the deformation fundamentals for the development of high performance TRIP steels.},
doi = {10.1016/j.commatsci.2010.10.002},
journal = {Computational Materials Science, 50(2):720-730},
number = ,
volume = ,
place = {United States},
year = 2010,
month =
}
  • In this paper, the separate effects of austenite stability and its volume fraction on the deformation behaviors of transformation-induced plasticity (TRIP) steels are investigated based on the microstructure-based finite element modeling method. The effects of austenite stability on the strength, ductility and formability of TRIP steels are first examined based on the microstructure of a commercial TRIP 800 steel. Then, the separate effects of the austenite volume fraction on the overall deformation behaviors of TRIP steels are examined based on the various representative volume elements (RVEs). The computational results suggest that the higher austenite stability is helpful to increase themore » ductility and formability, but not the UTS. However, the increase of austenite volume fraction alone is not helpful in improving the performance of TRIP steels. This may indicate that various other material factors should also be concurrently adjusted during thermo-mechanical manufacturing process in a way to increase the performance of TRIP steels, which needs further investigation.« less
  • Tensile behavior of two TRIP steels was investigated by in situ neutron diffraction. In the sample with a higher fraction of retained-austenite, the first load transfer was observed from the soft ferrite matrix to the hard retained austenite prior to martensitic transformation, while a second load transfer occurred from the austenite to the harder martensite as martensitic transformation was induced. In the sample with less retained-austenite, the martensitic transformation was limited, leading to significantly less tensile ductility.
  • The recrystallization behavior of three Nb-bearing, high-strength low-alloy (HSLA) steels was investigated during multipass deformation under continuous cooling conditions. The niobium concentrations of these steels varied from 0.05 to 0.09 wt pct. The specimens were tested on a computerized torsion machine using a simulation schedule of 17 passes. Deformation temperatures of 1,180 C to 700 C were employed, together with pass strains of 0.1 to 0.7, strain rates of 0.2 to 10 s[sup [minus]1]. and interpass times of 5 to 200 seconds. By means of mean flow stress vs 1,000/T diagrams, the effect of the deformation conditions on the no-recrystallizationmore » temperature (T[sub nr] ), the temperature at which recrystallization is no longer complete, was determined. It decreases with increasing strain and also decreases slightly with increasing strain rate. There is a T[sub nr] minimum at times of about 12 [approximately] 15 seconds, and both increases and decreases from this value raise this characteristic temperature. When the interpass times are short, solute atoms control the rate of recrystallization, the extent of which decreases as the time is decreased. When the interpass times are long, precipitation takes place and retards recrystallization, so that the extent of softening decreases.« less
  • A continuum model is developed to examine the influence of martensite shape, volume fraction, phase transformation strain, and thermal mismatch on the initial plastic state of the ferrite matrix following phase transformation and on the subsequent stress-strain behavior of the dual-phase steels upon loading. The theory is developed based on a relaxed constraint in the ductile matrix and an energy criterion to define its effective stress. In addition, it also assumes the martensite islands to possess a spheroidal shape and to be randomly oriented and homogeneously dispersed in the ferrite matrix. It is found that for a typical water-quenched processmore » from an intercritical temperature of 760 C, the critical martensite volume fraction needed to induce plastic deformation in the ferrite matrix is very low, typically below 1 pct, regardless of the martensite shape. Thus, when the two-phase system is subjected to an external load, plastic deformation commences immediately, resulting in the widely observed 'continuous yielding' behavior in dual-phase steels. The subsequent deformation of the dual-phase system is shown to be rather sensitive to the martensite shape, with the disc-shaped morphology giving rise to a superior overall response (over the spherical type). The stress-strain relations are also dependent upon the magnitude of the prior phase transformation strain. The strength coefficient h and the work-hardening exponent n of the smooth, parabolic-type stress-strain curves of the dual-phase system also increase with increasing martensite content for each selected inclusion shape. Comparison with an exact solution and with one set of experimental data indicates that the theory is generally within a reasonable range of accuracy.« less
  • As the result of features of their crystalline structure with a body-centered cubic lattice ferritic chromium corrosion-resistant steels, used primarily in the form of thin cold-rolled sheets for formed parts of industrial and domestic machinery, are very sensitive to a change in mechanical properties under the influence of plastic deformation. Three groups of corrosion resistant steels were investigated. 3 figs., 1 tab.