| Popis: |
TEM/STEM-EDS methods for the quantitative assessment of geometrical parameters, chemical composition and crystal structure of second phase particles are reviewed. Significant applications are discussed with regard to different ferritic steels : Interstitial Free (IF) steel for deep drawing, electrical 1%Si steel and enameling steel. After short term isothermal annealing, a Ti-containing IF steel exhibited Ti(C,N) precipitates that were finer and more frequent than Ti 4 C 2 S 2 . Ti(C,N) was a preferential site for Ti 4 C 2 S 2 nucleation. The experimental results were compared with calculations by a mathematical model of precipitation. Analysis of second phase particles in an electrical 1% Si steel after isothermal annealing allowed evaluation of the inhibition factor for grain growth. The abnormal grain growth in this steel was mainly due to dissolution of Cu 1.92 S and Ostwald ripening of (Mn,Cu)S and Ti(C,N) with AIN. Quantitative investigation of precipitates in an enameling steel, together with hydrogen permeation measurements, showed that interstitial sites at the surface of coherent e-Ti(C,N) precipitates act as efficient traps for hydrogen atoms. |
