Metallurgical design of high strength austenitic Fe-C-Mn steels with excellent formability

AUTHOR/S: A. Ferraiuolo, A. Smith PAPER PRESENTED TO: RFSR-CT-2005-00030 DATE: March 2010

ABSTRACT

Twinning induced plasticity (TWIP) steels are austenitic steels characterised by good combination between high tensile properties and high ductility. This behaviour is due to the characteristic high work hardening rate determined by the occurrence of deformation induced twinning during deformation. These properties are extremely attractive for automobile applications expecially for parts devoted to energy absorption (crashworthiness) and for structural reinforcement (body in white). TWIP steels are characterised by  • Austenite phase stability obtained with carbon and high manganese content (typically >16%). • Low stacking fault energies (SFE) leading to the ability to be deformed by means of both dislocation slip and mechanical twinning. The relative intensity of deformation mechanisms depends upon the chemical composition (mainly the carbon and manganese contents). . The main objectives of this project are:  1. To complete the understanding of the TWIP steel metallurgy particularly for what regard the following fields: • Solidification microstructure; • Recrystallization behaviour (dynamic and static) and texture formation.  • Tensile properties and work hardening ability, precipitation behaviour as a function of the steel chemical composition and its influence on the strip properties. • Influence of steel chemical composition on microstructure, mechanical properties, strain hardening behaviour as well as on application properties such as formability, weldability and coatability.  2. To design a metallurgically based manufacturing route (hot/cold rolling process, annealing treatment) taking into account the specific capability of the DUFERCO plants.

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