Formabilities of C-Si-Al-Mn Transformation-Induced Plasticity-Aided Martensitic Sheet Steel

Abstract:

The substitution of Si with Al in 0.2%C-1.5%Si-1.25%Mn-0.2%Cr ultrahigh strength transformation-induced plasticity (TRIP)-aided martensitic (TM) sheet steel improves galvanization. The effect of Al content on the microstructure and formabilities of the TM steel was therefore investigated. Replacement of Si with Al maintained the high volume fraction of the retained austenite and the high stretch-formability and stretch-flangeability, whereas it decreased the tensile strength. Complex addition of Si and Al yielded the best formabilities with 1.5 GPa tensile strength grade. The superior formabilities of Si-Al bearing TM steel were attributed to the strain-induced transformation of the metastable retained austenite and the relatively soft lath-martensite structure matrix. The former leads to plastic relaxation of the localized stress concentrations, thus suppressing void formation.

• Periodical: Materials Science Forum (Volumes 838-839)
• Pages: 546-551
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.838-839.546
• Online since: January 2016
• Authors: Junya Kobayashi*, Yumenori Nakashima, Koh Ichi Sugimoto, Goroh Itoh
• Keywords: Formability, Martensite, Retained Austenite, TRIP Steel

References

[1] K. Sugimoto, J. Sakaguchi, T. Iida, T. Kashima, Stretch-flangeability of a high-strength TRIP type bainitic sheet steel, ISIJ Int., 40 (2000) 920–926.

DOI: 10.2355/isijinternational.40.920

[2] H. Aydin, E. Essadiqi, I. Jung, S. Yue, Development of 3rd generation AHSS with medium Mn content alloying compositions, Mater. Sci. Eng. A, 564 (2013) 501–508.

DOI: 10.1016/j.msea.2012.11.113

[3] J.G. Speer, D.V. Edmonds, F.C. Rizzo, D.K. Matlock, Partitioning of carbon from supersaturated plates of ferrite, with application to steel processing and fundamentals of the bainite transformation, Solid State Mater. Sci., 8 (2004) 219–237.

DOI: 10.1016/j.cossms.2004.09.003

[4] V.F. Zackay, E.R. Parker, D. Fahr, B. Bush, The enhancement of ductility in high-strength steels, Trans. Am. Soc. Met., 60 (1967) 252–259.

[5] K. Sugimoto, M. Murata, S-M. Song, Formability of Al–Nb bearing ultra high-strength TRIP-aided sheet Steels with bainitic ferrite and/or martensite matrix, ISIJ Int., 50 (2010) 162–168.

DOI: 10.2355/isijinternational.50.162

[6] K. Sugimoto, J. Kobayashi, Newly developed TRIP-aided martensitic steels, Proc. Materials Science & Technology 2010 Conference & Exhibition (Recent Developments in Steel Processing), TMS, Warrendale, PA, 1639–1649.

[7] J. Kobayashi, D.V. Pham, K. Sugimoto: Stretch-flangeability of 1. 5GPa grade TRIP-aided martensitic cold rolled sheet steels, Steel Res. Int. (Special Edition), 81 (2011), 598-603.