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QUANTITATIVE ANALYSIS OF BANDED STRUCTURES IN DUAL-PHASE STEELS
June 2010
BENOIT KREBS, ALAIN HAZOTTE, LIONEL GERMAIN AND MOHAMED GOUNÉ
Dual-Phase (DP) steels are composed of martensite islands dispersed in a ductile ferrite matrix, which provides
a good balance between strength and ductility. Current processing conditions (continuous casting followed by
hot and cold rolling) generate ‘banded structures’ i.e., irregular, parallel and alternating bands of ferrite and
martensite, which are detrimental to mechanical properties and especially for in-use properties. We present an
original and simple method to quantify the intensity and wavelength of these bands. This method, based on
the analysis of covariance function of binary images, is firstly tested on model images. It is compared with
ASTM E-1268 standard and appears to be more robust. Then it is applied on real DP steel microstructures and
proves to be sufficiently sensitive to discriminate samples resulting from different thermo-mechanical routes.
Banded Structure, Covariance Function, Quantitative Microscopy, Steel
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