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Effect of pre-straining and bake hardening on the microstructure and mechanical properties of CMnSi trip steels

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journal contribution
posted on 2009-06-01, 00:00 authored by L Zhang, Ilana Timokhina, A La Fontaine, S Ringer, Peter HodgsonPeter Hodgson, E Pereloma
The effects of pre-straining and bake hardening on the mechanical behaviour and microstructural changes were studied in two CMnSi TRansformation-Induced Plasticity (TRIP) steels with different microstructures after intercritical annealing. The TRIP steels before and after pre-straining and bake hardening were characterised by X-ray diffraction, optical microscopy, transmission electron microscopy, three dimensional atom probe and tensile tests. Both steels exhibited discontinuous yielding behaviour and a significant strength increase with some reduction in ductility after pre-straining and bake hardening treatment. The following main microstructural changes are responsible for the observed mechanical behaviours: a decrease in the volume fraction of retained austenite, an increase in the dislocation density and the formation of cell substructure in the polygonal ferrite, higher localized dislocation density in the polygonal ferrite regions adjacent to martensite or retained austenite, and the precipitation of fine iron carbides in bainite and martensite. The mechanism for the observed yield point phenomenon in both steels after treatment was analysed.

History

Journal

Metallurgia Italiana

Volume

101

Issue

6

Pagination

49 - 55

Publisher

Assoc Italiana Metallurgia

Location

Milan, Italy

ISSN

0026-0843

Language

eng

Publication classification

C1 Refereed article in a scholarly journal; C Journal article

Copyright notice

2009, Associazione Italiana Di Metallurgia