E: Procedure Metz 
Tt | Cu-1.3wt.%Yb (alloy A) and Cu-1.3wt.%Er (alloy B) alloys were prepared by te en 
in 1 melting using high purity elements as starting materials. The resulting bars (200 OZ or 
mm long and 40 mm diameter) were rapidly solidified by a Chill-Block Melt Spinning Technique STE A 
under an Ar atmosphere using a graphite crucible 48 mm in inner diameter and nozzle with an WE 
orifice diameter of 0.8 mm, followed by ejection with an Argon overpressure of 0.2-0.3 bars onto pe 
the surface of a copper-beryllium wheel rotating at speed of about 23 m/s. Continuous ribbons about ee 
3 mm in width and 60 to 100 pm in thickness were produced. The internal oxidation experiments fet 
were carried out at temperatures from 873 to 1273 K at an oxygen partial pressure equal to the ws 
decomposition pressure of cuprous oxide. To accomplish this the samples were packed in a mixture He 
of equal parts of cuprous oxide and copper metal powder and enclosed in a quarz ampoule. oe . 
Microstructure of the as-cast as well as internally oxidized samples was characterised in detail using 0 To 
optical microscopy (OM), scanning electron microscopy (SEM-Jeol JSM 840 A), scanning we in 
transmission electron microscopy (STEM-Jeol JEM 200 B) and EDX microanalysis (Link we 
Analytical AN 1000). The as-cast samples were prepared by electropolishing in a mixture of 60 7 ON 
vol.% H;PO4 and 40 vol.% HO, while the internally oxidized ribbons were etched in NH,OH-H,0, we 
solution. TEM foils of as-cast and completely internal oxidized ribbons were prepared by re : 
electropolishing in a solution CrO; in CH3COOH. oe 
Results and discussion 
The microstructures of the melt spun alloys A and B show very similar features as the 
microstructures of other rapidly solidified binary Cu-based alloys (5). The ribbons of both alloys 
consist of three different morphological zones - outer fine equiaxed zone, columnar grains and zone 
with coarse equiaxed grains - formed from the bottom to the upper surface of the ribbons (Fig. 1). 
In both rapidly solidified alloys the microstructure consists of supersaturated solid solution (0tcu 
phase) and fines dispersed Cu-RE intermetallic particles. The supersaturated f. c. c. solid solution 
phase was formed both in the fine equiaxed zone and at the beginning of the columnar zone. In the 
columnar zone the intermetallic particles are about 150 nm in size, while at the top of the coarse 
equiaxed zone the size of particles reached approximately 300 nm diameter in the alloy A and 250 
nm in the alloy B respectively. In both alloys the segregation of the second phase was reduced to a 
scale, which could enable to obtain a fine dispersion of oxide particles at the subsequent 10. 
Fig. 2:01 
. The size 
the alloy 
With the 
Rest 
Inlermeta 
Oxidation 
Imig; 
0: 1 
: gr Inter st 
A 
men 
Fig.1: Microstructure of transverse cross-section of rapidly solidified ribbon of the alloy A. m ; 
246