In situ investigation of the iron carbide precipitation process in a Fe-C-Mn-Si Q&P steel

Sébastien Allain (1) , Samy Aoued (2, 3) , Angeline Poulon-Quintin (2) , Mohamed Gouné (2) , Frederic Danoix (3) , Jean-Christophe Hell (4) , Magali Bouzat (4) , Michel Soler (4) , Guillaume Geandier (1)

1 IJL - Institut Jean Lamour
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
3 GPM - Groupe de physique des matériaux
4 ArcelorMittal Maizières Research SA

Quenching and Partitioning (Q&P) steels are promising candidates for automotive applications because of their lightweight potential. Their properties depend on carbon enrichment in austenite which, in turn, is strongly influenced by carbide precipitation in martensite during quenching and partitioning treatment. In this paper, by coupling in situ High Energy X-Ray Diffraction (HEXRD) experiments and Transmission Electron Microscopy (TEM), we give some clarification regarding the precipitation process of iron carbides in martensite throughout the Q&P process. For the first time, precipitation kinetics was followed in real time. It was shown that precipitation starts during the reheating sequence for the steel studied. Surprisingly, the precipitated fraction remains stable all along the partitioning step at 400 °C. Furthermore, the analyses enable the conclusion that the iron carbides are most probably eta carbides. The presence of cementite was ruled out, while the presence of several epsilon carbides cannot be strictly excluded.

Mots clés: steel; Q&P; transition carbide; precipitation; HEXRD; TEM; steel

Domaines: Matériaux

Sébastien Allain, Samy Aoued, Angeline Poulon-Quintin, Mohamed Gouné, Frederic Danoix, et al.. In situ investigation of the iron carbide precipitation process in a Fe-C-Mn-Si Q&P steel. Materials, 2018, 11 (7), 1087 (11 p.). ⟨10.3390/ma11071087⟩. ⟨hal-01827552⟩