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In the eutectic structures of an alloy containing 0.5 % Mg one may wit 
observe already on an optical microscope (Fig. 7b) the presence of pre 
eut 
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Fig. 7a: Changes in zinc, aluminium, copper concentration in as-cast 
A1Zn70Mg0.5 alloy, 
b: Microstructure of as-cast AlZn70MgO0.5 alloy. The bright 7 
large spot with fine globular inclusions correspond to 
Lg + 2 MgZn; ) eutectic. Pictures taken with back-scatte- 
red electrons, compo mode, with microprobe trace of 
csizinc, 
d: magnesium. 
the brighter spots of the binary ols + 2 (MgZng) eutectic - of a 
540