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Structural work-hardening : martensitic steels

Microstructure and deformation mechanisms in last generation martensitic steels

Staff: Armand Coujou, Joël Douin, Florence-Pettinari-Sturmel, Vanessa Vidal

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(a) STEM image of the ML1014 steel. (b) EELS spectrum obtained in the area noted (1) located in a carbide (a noticeable peak indicates the presence of Cr) and in the area noted (2), i.e. within the Fea matrix.

This work, which is linked to the research program AMARAGE financially supported by the ANR (Agence Nationale de la Recherche), participates to the development of new high performance steels combining high mechanical resistance and improved toughness for aeronautic applications, in collaboration with the Aubert & Duval industrial group.

A double precipitation of carbides and intermetallic phases has been developed to increase the strength of the steels. This solution greatly improves the mechanical performance of steels.

Up to now, no fundamental research has been carried out in this area, which is just emerging, and a lot of fundamental investigations must be done.


As the mechanical properties are controlled by the interactions between the dislocations and the complex microstructure, an effort is made to obtain a precise characterization of the precipitation, the kinetic of this precipitation and of course the deformation micromechanisms associated with this precipitation. A better understanding of the precipitation and its effect on the mechanical properties is an essential step in the development of new generation steels.

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MEHR images of a nanometric carbide (a) ; deformation field map around a carbide; MEHR images of several carbides (c)
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Interaction dislocations / precipitates interaction. Evidence of dislocation loops around the precipitates.