1) To understand the phenomenon of dynamic strain ageing (DSA) in high Mn twinning-induced plasticity (TWIP) steels, one has to study the effect of point defect complexes (i.e., vacancy-C) and their interaction with partial dislocations and also with stacking faults in TWIP steels. Further, examine how this interaction can explain the suppression of DSA in Al alloyed TWIP steels (Al alloying addition increases the stacking fault energy of TWIP steels).  

2) Please see whether my draft notes on Portevin–Le Chatelier effect/serrated flow and dynamic strain ageing may be of help to your work (please attachment). 

The following papers on DSA in TWIP steels may be useful to you:

1) "Effects of Static and Dynamic Strain Aging on Hydrogen Embrittlement in TWIP Steels Containing Al", Motomichi KOYAMA et al., ISIJ International, Vol. 53 (2013), No. 7, pp. 1268–1274.

2) "Work hardening associated with ε-martensitic transformation, deformation twinning and dynamic strain aging in Fe–17Mn–0.6C and Fe–17Mn–0.8C TWIP steels", Motomichi Koyama et al, Materials Science and Engineering A 528 (2011) 7310– 7316.

3) "On the origin of dynamic strain aging in twinning-induced plasticity steels", Seok-Jae Lee et al, Acta Materialia 59 (2011) 6809–6819.

4) "Localized Deformation due to Portevin–LeChatelier Effect in 18Mn–0.6C TWIP Austenitic Steel", Lei CHEN et al, ISIJ International, Vol. 47 (2007), No. 12, pp. 1804–1812.

Best wishes.

Thanks very muchu for your kind reply! I will study these issues now.

Thanks so much for you Prof. Phaniraj. 

To add on further, the high Mn steels such as TWIP steels have an excellent combination of strength and uniform ductility in addition to wear resistance. Addition of Al suppresses DSA,  and improves its resistance to hydrogen delayed fracture. You may also see these Reviews in this subject on TWIP steels and DSA effect in these steels.

1) "High manganese austenitic twinning induced plasticity steels: A review of the microstructure properties relationships", O. Bouaziz et al, Current Opinion in Solid State and Materials Science 15 (2011) 141–168.

2)"Performance and Characterization of TWIP Steels for Automotive Applications", R. W. Neu, Materials Performance and Characterization, Vol. 2, No. 1, 2013, pp. 244-284, doi: 10.1520/MPC20130009. ISSN2165-3992.

3) In Book: "Advanced Steels: The Recent Scenario in Steel Science and Technology" Springer 2011, Edited by Yuqing Weng, Han Dong, Yong Gan :- Please see Chapter on "Microstructure and Mechanical Properties of  Al-Added High Mn austenitic  Steel" by Jae-Eun Jin and Young-Kook Lee.

Dear  Prof. Phaniraj, I think that the DSA effect may facilitate the work hardening behavior. Because the C in TWIP steel can increase its ultimate strength and elongation. Although the C atom increase its Stacking fault energy. So how about others to figure out this controversy?

Though I have not worked on DSA in TWIP steels, I have conducted research on DSA and serrated flow behavior in Alloy D9 (Ti modified Type 316 stainless steel). Serrated flow is one of the manifestation of DSA; DSA is the interaction of diffusive solute species and mobile dislocations, and it is well recognized in all the models of DSA that  the strain rate sensitivity becomes negative in the DSA domain of strain rate and temperature.  

Generally in the DSA regime where serrations are observed, it is noticed that the work-hardening rate will show a peak, while the flow stress (yield stress or tensile strength) exhibits either a plateau or a peak. The elongation measured as total ductility or uniform ductility exhibits a minima (a trough). Strain rate sensitivity of  the flow stress decreases and exhibits negative (negative SRS: please see paper by P. Penning, Acta Metall., 1972, 20, p. 1169) in the region of PLC effect/DSA and this is a crucial factor to recognize the signature of DSA. 

Thanks for your kind reply, I think that the C atom in TWIP steel is very interesting. Because the DSA effect combined with the extraordinary mechanical property.

Yes but Al effect in suppressing DSA is important to understand the mechanism of DSA.

That's all right. I focus on the strain rate sensitivity of Al-added TWIP steel, I find that DSA contributes to the negative SRS. But I want to observe the evolution of C atoms with DSA. except the tensile curves, is there existing any other method?

Please see the paper by R. A. Mulford and U. F. Kooks, Acta metallurgica, 1979, vol. 27, p. 1125.

Thanks, I hope we can get a coopearation in the future.

Thanks for your kindness and do hope so. 

For general introduction of Serrated Yielding, Models of DSA : Please see my notes that I had attached and the paper by P. Rodriguez. 

In my notes on PLC effect and DSA,  I have described what are the various manifestations of DSA. In this notes, I have also given the chronological development of the subject of DSA. In case you have difficulty, you may start with the Short and Excellent Review by P. Rodriguez on serrated plastic flow.

1) "Serrated Plastic Flow" by P. Rodriguez, Bulletin of  Material Science, September 1984, vol. 6, No. 4 pages 653-663 (This is a short and well written review).

For 'activation energy determination for serrated flow by various methods': please see: 

2) "Activation energy for serrated flow in a 15Cr-5Ni Ti-modified austenitic stainless steel" by S. Venkadeasn, C. Phaniraj, P.V. Sivaprasad and P. Rodriguez, Acta Metallurgica Et  Materialia, 1992, Vol. 40, No. 3, pp. 569-580.

For nucleation and propagation of PLC bands in TWIP steel (PLC bands can be continuously propagating band as in the case of Type A serrations or discontinuous hopping band as in the case of Type B serrations): please see:

3) "Nucleation and Propagation of Portevin-Le Châtelier Bands in Austenitic Steel with Twinning Induced Plasticity" by Louis G. Hector, Pablo D.   Zavattieri, Experimental and Applied Mechanics, Volume 6,  Conference Proceedings of the Society for Experimental Mechanics Series 2011, pp 855-863. 

4) For PLC bands and on collective behavior of dislocations: please see: 

(a) "TOPICAL REVIEW: The Portevin–Le Chatelier effect: a review of experimental findings", by Ahmet Yilmaz, Sci. Technol. Adv. Mater. 12 (2011) 063001 (16pp): doi:10.1088/1468 6996/12/6/063001.

(b) "Spatiotemporal analysis of Portevin–Le Chaˆtelier deformation bands: Theory, simulation, and experiment", P. Hahner et al., PHYSICAL REVIEW B, 2002, VOLUME 65, 134109. (DOI: 10.1103/PhysRevB.65.134109).

(c) "Investigating the Portevin–Le Châtelier effect by the acoustic emission and laser extensometry techniques", František Chmelı́k et al., Materials Science and Engineering: A, Volume 324, Issues 1–2, 15 February 2002, Pages 200–207.

(d) "Current theoretical approaches to collective behavior of dislocations", by G. Ananthakrishna, Physics Reports 440 (2007) 113 – 259.

Best wishes.

Happy Chinese new year for you, Dear Professor Raabe. Sorry for the late reply, because we have the winter holiday last month. Thanks for your kind and fruitful suggestion. Recently I find that the DSA effect can influence the twinning evolution in FeMnC TWIP steel, and you can find the attachment here. But I do not know what kind of measurement can observe the interaction between them. Maybe after reading your paper, I can find the effective observation method. Best regards!

The paper by Prof. Dierk Raabe's group (Acta Mater. 2015) on DSA at atomic scale in Al - 4.8 at. % Mg is educative and very interesting. And thanks Dr. Omid Majidi for your encouraging words.

Best wishes Dr  Hao Kun Yang for your research.

Thanks so much for your blessing, Professor Phaniraj!