No abstract

The present investigation aims at a better understanding of the aging microstructure of a high‐nitrogen (0.11%N) 12%Cr steel with a view of optimizing the mechanical properties. The precipitation behaviour is rather complex. The dissolution of the numerous kinds of precipitates and their precipitation are studied by transmission electron microscopy for a wide temperature treatment domain between 200 and 1150°C. The microstructural evolutions are correlated to hardness measurements with the outcome of the determination of heat treatment parameters required to achieve the maximum of secondary hardening.

No 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.