corresponding to the equilibrium concentration lying on the liquidus line at the actual I0 jue 
temperature. Because of very fine dispersed intermetallic particles in the starting rapidly solidified 1 
ribbons the microstructure in the UTPZ consists of acy solid solution and fine dispersed liquid 4 
phase inside the matrix (200 to 500 nm in size). The size of such "islands of liquid" (IL) in the 
matrix and the distance between them depend on the IO temperature. The higher the temperature, 
the bigger are IL and the shorter is the mean distance between them. 
Conclust 
The presen 
microstrud 
mechanısm 
Internal © 
Oxidation ( 
In the sem 
i 
Fig. 3: Optical micrograph of the alloy B after partial IO at 1073 K. He 
Referens 
NAS 
MIEN 
mA Ay 
(4) J R G 
(5) L Ani 
6)W. 
Fig. 4: SEM chemical mapping of oxide particles in the region of former IL. 
In such a system the IO process starts with the dissolution of atomic oxygen into the oc, matrix and 
its diffusion in the sample interior. At the solid/liquid interface the oxygen atoms dissolve in the 
melt and afterwards the solubility product for the RE oxide is exceeded and the critical 
supersaturation for homogeneous precipitation is attained, the RE oxide particles precipitates from 
the liquid phase at the solid liquid interface. Since the RE alloying element is removed by oxidation 
process, the melt around the particles becomes undercooled. Degree of undercooling increases with 
time of precipitation i. e. with lowering the concentration of alloying element. At the critical value 
the melt at the oxide particles solidifies and creates the layer of oc, (marked with the arrow in Fig. 
248