Fifth European Symposium on Martensitic Transformations and Shape Memory Alloys

J. Phys. IV France 11 (2001) Pr8-223-Pr8-228
DOI: 10.1051/jp4:2001838

On the influence of aluminium content on the stability of retained austenite in multiphase TRIP-assisted steels

A. Mertens¹, P. Jacques^{1, 2}, R. Lazarova^{1, 3}, L. Zhao⁴, J. Sietsma⁴ and F. Delannay<sup>1

1</sup>  Université Catholique de Louvain, Département des Sciences des Matériaux et des Procédés, PCIM, place Sainte-Barbe 2, 1348 Louvain-la-Neuve, Belgium
²  McGill University, Department of Metallurgical Engineering, 3610 University Street, Montreal H3A 2B2, Quebec, Canada.
³  Bulgarian Academy of Sciences, Institute of Metal Science, Shipchensky Prohod St. 67, Bg-1574 Sofia, Bulgaria.
⁴  Delft University of Technology, Laboratory for Materials Science, Rotterdamseweg 137, 2628 AL Delft, The Netherlands

Abstract
TRIP-assisted multiphase steels show enhanced mechanical properties thanks to the strain-induced transformation of retained austenite to martensite (TRIP effect). Stabilization of austenite is made possible by the combination of appropriate chemical composition and heat-treatment. It has been shown recently that aluminium could be substituted to silicon, whose effect has been mainly studied in the literature so far, for this austenite retention. In this work, the influence of aluminium content and heat-treating conditions on the retention of carbon-enriched austenite is investigated in two 0.12 wt. % C - 1.5 wt. % Mn steels with 0.51 wt. % Al and 1.16 wt. % Al respectively. Special attention is given to the effect of aluminium on the phenomena developing during bainitic holding. The bainitic transformation kinetics is followed by dilatometry. Coupled with a characterization of the microstructures by X-ray diffraction, scanning electron microscopy and image analysis, these dilatometry experiments enabled us to draw transformation maps giving the volume fractions of the different phases. The retarding effect of aluminium on carbide precipitation during the bainitic transformation is highlighted, although Al appears less efficient than Si.

© EDP Sciences 2001