Prakt. Met. Sonderband 38 (2006) 157 
supersaturated solid solution. The composition of the particles has been analyzed by 
energy-dispersive spectroscopy and was found close to the CusZr compound. Their volume 
is overestimated by the classical qualitative and quantitative metallography because of 
undesired overetching 
zn 
an 
Juiaxed 
Fig. 2: Banded structure in transverse (a) and horizontal (b) cross-section 
. 1c) with 
probably It can be seen also, that the appearance of the columnar-equiaxed transition strongly 
transition increases the degree of microsegregation. Nevertheless the zirconium intermetallic was 
“abruptly. mostly finer than 1 um. 
direction, The microstructural morphology is dependent on the local conditions at the solid liquid 
e ribbons interface. At all ribbons nucleation occurred along the surface in contact with the quenching 
reported substrate (outer equiaxed grains). After these grains nucleate, they grow towards the top of 
5 cellular the casting which leads to the so-called columnar zone. 
unstable. The transition from the outer equiaxed grains to the columnar zone, as well as the grain 
ıds which selection which occurs in a distance of a few hundreds nm from the contact surface is 
practically impossible to observe and analyze in the samples prepared by standard 
structure metallographic technique. The same problems exist during investigation of the upper edge 
Jaries. As of the equiaxed zone near the free surface. In both cases there was the problem to produce 
zone that good edge retention. Additionally, because of the small dimensions of the ribbons and 
rains and submicron grains the edge region of the samples contained artefacts that hindered the 
correct interpretation of the microstructure. Therefore we decided to use FIB preparation 
1at these with 3D microscopy. 
on where 
from the