WE, 
volume fraction to low volume fraction, i.e. from bottom to top (fig. 2b). After approximately 1h, 
the former mushy zone has resolidified completely, and a stationary concentration profile is attained 
: (fig. 2.c). The measured concentrations correspond to the solidus concentrations as given by the 
: phase diagram at the local temperature. 
am Y temperature [°C] 
. | 500 550 575 600 625 650 
He uy So liquidus line |. oo solidus ~~, 
liduid solidus 
ERE electron 650 NT N q ! concentration | 
_ A 5 2 | temperature 
Co . ; / 
625 % solidus line 3 . * 
— 4 \ = . 
75 600 o + liduid Z NES 
vw °c, = 5 To 
ly illustrated © . ) Co 
ing 2 stationary ‘5 575 B 6. 
ems Tn te ; eutectic | 6-7 _- 
ton forms (fie r i % X 
’ m (fig, + 550 ı line 2 oo, 
ey um © 8 ' ’ - 
Xoo the 4 = 
Ww dBi a 525} x +ALCu 9 - = “a - 
y diffusion and x columnar So 
¢ solute cent : 10 ; a 
Ve en ; 2, » equiaxed su 
“2000s of hich 500Lu™ A | CL 14 ' co 
Al 1 2 3 45 6 7 8 9 o * 23 4 5 5 
concentration of Cu [wt%)] concentration of Cu [wt%)] 
Fig.3: Al-rich corner of the Al-Cu Fig.4: Temperature gradient and 
phase diagram concentration profiles 
Results 
Significant changes of grain structure and concentration distribution along the cylinder axis are 
already observed after a few minutes. In the directionally solidified samples, the grain structure 
remains columnar. Elongated grains with concentrations between maximum solubility (5.7wt%Cu) 
and approx. 0.8wt%Cu extend over the ranges of the former mushy zone (i.e. approx. 10mmThe 
lowest concentration in the solid at the plane interface corresponds approximately to the solid 
concentration in the phase diagram at liquidus temperature (fig. 4).). The length scale of the initial 
microstructure, particularly the primary dendrite spacing is not maintained during the process. As 
o 
315