Die entstehenden Spannungen beim Abkühlen nach dem Verschweißen wurden mit dem 
Polarisationsmikroskop untersucht. Anhand spannungsoptischer Aufnahmen wurde 
gezeigt, daß beim Verschweißen von gleichen Materialien keine meßbaren Spannungen 
auftreten (Fig. 3). Werden Gläser mit unterschiedlichen thermischen 
Ausdehnungskoeffizienten verbunden, lassen sich Aussagen über die Richtung der 
Hauptspannungen (Isoklinen) (Fig. 4) und die Höhe der maximalen Schubspannungen 
(Isochromaten) machen. Durch Verwendung eines A -Plattchens lassen sich die 
Isochromaten bei den verwendeten Materialien besonders gut zeigen. Die 
Isochromatenordnung an der Kante ist hoher als die im Bereich der Kerbspitze. 
Metallographic preparation and EDX measurements on glass —glass —composites. 
ABSTRACT 
Glass —glass composites have been diffusion bonded in order to investigate the influence of 
thermal stresses on bond strength (Tab. 1). In this work the metallographic preparation 
and experimental methods are reported. 
The preparation technique involved wet —grinding using SiC papers from grade 320 to 
4000 with subsequent polishing using 2 um ceriumoxide on a fine cloth. Removal of 
scratches during polishing was found to be easier on the harder glasses. 
The prepared specimens were bonded in a muffle furnace. The quality of the bond was 
investigated using an optical microscope either by viewing directly through the bond 
interface or by preparation of a transverse section. Pores and unbonded regions could be 
found easily. 
Diffusion zones in the interface region have been investigated by EDX and interference 
microscopy. The influence of a shorter hold time on the width of the diffusion zone was 
determined by EDX and it is demonstrated that interference microscopy is an additional 
way to estimate the width of the diffusion zone (Figs. 1, 2). 
Thermal stresses produced on cooling following bonding have been investigated with the 
aid of a polarisation microscope. It is shown that bonding two identical glasses produces 
no measurable stresses (Fig. 3). When two dissimilar glasses are bonded one can 
determine the directions of the equivalent stresses (isoclinic fringes) (Fig. 4) and 
magnitudes of the maximum shear stresses (isochromatic fringes). By using a A -plate one 
can readily observe the different isochromatic fringes. The order of the isochromatic 
fringes at the edge of the bond is higher than in the region of the notch. 
Prakt. Met. Sonderbd. 21 (1990) 
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