Fatigue Behavior of High Manganese TWIP Steels and of Low Alloy Q&P Steels for Car-Body Applications

Abstract:

The automotive TWIP steels are high-Mn austenitic steels, with a relevant C content, which exhibit a promising combination of strength and toughness, arising from the ductile austenitic structure, which is strengthened by C, and from the TWIP (TWinning Induced Plasticity) effect. The microstructure of the low-alloy Q&P steels consists of martensite and austenite and is obtained by the Quenching and Partitioning (Q&P) heat treatment, which consists of: austenitizing; quenching to the T_q temperature, comprised between M_s and M_f; soaking at the T_p partitioning temperature (T_p being equal to or slightly higher than T_q) to allow carbon to diffuse from martensite to austenite; and quenching to room temperature. The fatigue behavior of these steels is examined both in the as-fabricated condition and after pre-straining and welding operations, which are representative of the cold forming and assembling operations performed to fabricate the car-bodies. Moreover, the microscopic fracture mechanisms are assessed by means of fractographic examinations.

• Periodical: Materials Science Forum (Volumes 783-786)
• Pages: 713-720
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.783-786.713
• Online since: May 2014
• Authors: Paolo Matteis*, Giorgio Scavino, R. Sesana, F. D’Aiuto, Donato Firrao
• Keywords: Automotive, Partitioning, Quenching, Steel Sheets, TWIP

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