Free Access
Microsc. Microanal. Microstruct.
Volume 6, Number 5-6, October / December 1995
Page(s) 633 - 646
Microsc. Microanal. Microstruct. 6, 633-646 (1995)
DOI: 10.1051/mmm:1995153

TEM-EDS Characterization of Second Phases in Ferritic Steels

Susanna Matera et Ettore Anelli

Centro Sviluppo Materiali S.P.A, P.O. Box 10747, Roma-EUR, Italy

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 $\rm Ti_4C_2S_2$. Ti(C,N) was a preferential site for $\rm Ti_4C_2S_2$ 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 $\rm Cu_{1.92}S$ and Ostwald ripening of (Mn,Cu)S and Ti(C,N) with AlN. Quantitative investigation of precipitates in an enameling steel, together with hydrogen permeation measurements, showed that interstitial sites at the surface of coherent $\epsilon$-Ti(C,N) precipitates act as efficient traps for hydrogen atoms.

8130M - Precipitation.
8140G - Other heat and thermomechanical treatments.
6155H - Crystal structure of specific alloys.
6475 - Solubility, segregation, and mixing.
6480E - Stoichiometry and homogeneity.
6630F - Self diffusion in solid metals, semimetals, and alloys.

Key words
annealing -- crystal structure -- diffusion -- grain growth -- nucleation -- precipitation -- scanning transmission electron microscopy -- steel -- stoichiometry -- transmission electron microscopy -- X ray chemical analysis -- grain growth -- second phases -- ferritic steels -- TEM STEM EDS methods -- quantitative assessment -- geometrical parameter -- chemical composition -- crystal structure -- second phase particles -- review -- interstitial free steel -- deep drawing -- electrical steel -- enameling steel -- short term isothermal annealing -- Ti containing IF steel -- Ti C,N precipitates -- Ostwald ripening -- Ti sub 4 C sub 2 S sub 2 nucleation -- precipitation -- isothermal annealing -- inhibition factor

© EDP Sciences 1995