Prakt. Met. Sonderband 38 (2006) 89 
Analysis of merged LOM and SEM pictures using innovative 
- image processing methods 
containing 
ha a Corinna Thomser*, Michael Unger**, Zifang Zhang**, Jens Rainer Ohm**, Wolfgang Bleck* 
PALA * Institute of Ferrous Metallurgy, RWTH Aachen University, Germany 
** Institute of Communications Engineering, RWTH Aachen University, Germany 
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Multiphase steels play an important role for the automotive industry. Their mechanical 
properties are strongly influenced by the microstructure. A quantitative description of the 
microstructure is necessary to optimise the properties of multiphase steels through a 
precise microstructure design. Using only light optical microscopy (LOM), the 
characterisation of multiphase steels cannot be achieved sufficiently due to the fact that 
Sei very fine metallographic constituents are present, which are smaller than the optical 
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resolution limit. This problem can be avoided by using scanning electron microscope 
(SEM) images in addition to the light optical images. Common commercial pixel - based 
software tools for metallographic applications are not able to analyze the phases in 
multiphase steels sufficiently. 
Within this work, we describe a method for automatic composing LOM and SEM images 
. into a single feature image. In addition, we present a novel segment based approach, 
fob on which classifies different phases in images of multiphase steels. Thereby we use several 
¥ Seminar, features of the derived segments for the classification process. 
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1. INTRODUCTION 
3, p. 1-9 Multiphase steels play an important role for the automotive industry, e.g. if we look at 
cep international projects like the ULSAB project, especially dual phase steels are favourable 
s”, In: used for modern cars (Figure 1). Dual phase steels are composed of a soft ferritic matrix 
with hard inclusions of martensite which causes a good formability and a high strength 
level. 
ULSAB-AVC PNOV-Class Boddy Structure 
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Figure 1: Future steel application in car bodies, according to international projects