Mechanical Behavior of TWIP steels

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Introduction

Twinning Induced Plasticity (TWIP) steels are class of austenitic steels with mechanically induced twin deformations.TWIP steels have highly desirable properties for automotive applications exhibiting both high strength and large ductility.The composition of TWIP steels is mainly a high amount of Mn, from 20-35 wt.% with alloying additions that may include <3% Al, <3% Si, <1.5% C and some other microalloying elements. TWIP steels are face centered cubic (fcc) with a low stacking fault energy (SFE) that promotes deformation twinning. The twinning increases the strength via additional hardening and extends ductility. The strength and ductility of these high Mn TWIP steels are considerably greater than all other classes of steels for automotive applications as illustrated in Fig. 1.[1]

Fig. 1. Strength and ductility of steels for automotive applications[1]

Stress-strain plots for TWIP steels

Fig. 2. True stress true strain curve (a) and normalized strain hardening rate curve as a function of the true strain (b) of the Fe-22Mn-0.6C fine-grained TWIP steel[2]
Fig. 3. Engineering stress-strain response of different advanced high strength sheet steels with 980 TWIP being Fe-18Mn-1.5Al-0.6C[1]
Fig. 4. Effect of grain size on tensile response of Fe-22Mn-0.6C TWIP steels< ref name=ref1/
Fig. 5. Engineering stress-engineering strain curves for TWIP steel samples with different grain sizes[3]
Fig. 6. The representative engineering stress-strain curves of Fe-28Mn-9Al-0.8C with three different grain sizes tested at 25 C with the initial strain rate of 10^-3 s^-1 (a), and the true stress-strain curves and the corresponding strain hardening rate as a function of true strain (b)[3]
Fig. 7. Engineering stress-strain curves of Fe-23Mn-2Al-0.2 steel at different deformation temperatures [3]
Fig. 8. Mechanical properties of the Fe-23Mn-2Al-0.2C TWIP steel deformed at different strain rates[3]


Fig. 9. Typical ranges for the mechanical properties of TWIP steel[4]
Fig. 10. Stress-strain curves Fe-18Mn-0.6C TWIP steel with increasing Al alloying additions. The additions delay the onset of the serrations, and at 2.3% Al no serrations are observed.[4]
Fig. 11. Influence of N alloying additions on the stress-strain curve of Fe-22Mn-0.6C TWIP steel[4]
Fig. 12. True stress-strain curves of single hit compression testing of TWIP steel under strain rate of 0.1 s^-1.[5]

Fatigue Behavior of TWIP steels

Fig. 15. Stress amplitude–fatigue life data for the investigated steels. Data for annealed Type 301LN and 316L austenitic stainless steels are included for comparison[6]
Fig. 16. Cyclic behavior of the investigated TWIP steels at three initial stress amplitudes.[6]
Fig. 17. Stress amplitude-fatigue life data and plots for 301 LN and 6C22 Mn TWIP steels with (a) ultra-fine grain structures and (b) coarse grain structures [7]


References

  1. 1.0 1.1 1.2 Neu, R. W. "Performance and Characterization of TWIP Steels for Automotive Applications." Materials Performance and Characterization 2.1 (2013): 244-284.
  2. D. Barbier, N. Gey, S. Allain, N. Bozzolo, M. Humbert, Analysis of the tensile behavior of a TWIP steel based on the texture and microstructure evolutions, Materials Science and Engineering: A, Volume 500, Issues 1–2, 25 January 2009, Pages 196-206, ISSN 0921-5093, http://dx.doi.org/10.1016/j.msea.2008.09.031.
  3. 3.0 3.1 3.2 3.3 Chen, Liqing, Yang Zhao, and Xiaomei Qin. "Some aspects of high manganese twinning-induced plasticity (TWIP) steel, a review." Acta Metallurgica Sinica (English Letters) 26.1 (2013): 1-15.
  4. 4.0 4.1 4.2 De Cooman, B. C., Jinkyung Kim, and Kwang-geun Chin. High Mn TWIP steels for automotive applications. INTECH Open Access Publisher, 2011.
  5. J. Hajkazemi, A. Zarei-Hanzaki, M. Sabet, S. Khoddam, Double-hit compression behavior of TWIP steels, Materials Science and Engineering: A, Volume 530, 15 December 2011, Pages 233-238, ISSN 0921-5093, http://dx.doi.org/10.1016/j.msea.2011.09.080. (http://www.sciencedirect.com/science/article/pii/S0921509311010513)
  6. 6.0 6.1 A.S. Hamada, L.P. Karjalainen, J. Puustinen, Fatigue behavior of high-Mn TWIP steels, Materials Science and Engineering: A, Volume 517, Issues 1–2, 20 August 2009, Pages 68-77, ISSN 0921-5093, http://dx.doi.org/10.1016/j.msea.2009.03.039.(http://www.sciencedirect.com/science/article/pii/S0921509309003633)
  7. A.S. Hamada, L.P. Karjalainen, High-cycle fatigue behavior of ultrafine-grained austenitic stainless and TWIP steels, Materials Science and Engineering: A, Volume 527, Issues 21–22, 20 August 2010, Pages 5715-5722, ISSN 0921-5093, http://dx.doi.org/10.1016/j.msea.2010.05.035.
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