Etude des phénomènes de précipitation dans un acier austénitique à 19% de chrome et 19% de manganèse, et à très forte teneur en azote

Abstract

This paper describes the precipitation evolution that occurs in a not presûained 1 %N Mn-Cr austenitic steel aged in the [400°C-900°C] temperature range, and for various times up to 150 hours. Themal treatrnents carried out between 7W°C and 900°C lead to a discontinuous precipitation of plates of Cr2N at grain boundaries. The nucleation stage of this precipitation reaction arises fiom the migration of the grain boundary dong the high-energy interface, in order to reduce the interfacial energy of the primary surface between the plate and the grain boundary. On the contrary, the ce11 growth is characterized by numerous properties that differ from the hypotheses of usual theories. These non-steady state growth features arise from the continuous modifications of the diffusion-controlled mechanisms during isothermal aging. Beside this cellular precipitation, the sigma phase forms with significant volume fractions in the cells.

Automatic image segmentation for material microstructure characterization by optical microscopy

“…In our work, we used the three micrographic images at 200 magnification of 2205 duplex stainless steel heattreated at temperatures respectively:800•C, 850•C and 950•C. Clearly and obviously, after observing the Figure 1, we notice that the three micrographic images of steel contain three different zones: Ferrite, austenite and the third zone known as sigma phase [11][12]; with 30 atoms per mesh (Fig 2).…”