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Be Results and discussion 
Due to the volatilization of aluminum during vacuum arc melting, it is difficult to reach the 
desired composition. After melting, targeted eutectic composition was slightly enriched in 
aluminum. The typical microstructure of the slightly hypoeutectic alloy after melting, consists of 
lamellar and rod-like eutectic, RuAl primary dendrites, and Ru enriched zones, so called halos, 
around RuAl primary dendrites. 
When conducting nanoindentations, it is important to limit the maximum applied force in 
order to make indentation in desired region in the microstructure. In study of local mechanical 
properties of Waspalloy, Goken et al.[10, 11] used maximum force of 100 uN (this value is the 
’ lower limit of the applied method to get plastic indents) to make indentations in very fine ’ 
onases. precipitates (110 and 27 nm). The same authors reported that the application of the force of 500 uN 
resulted in destruction of Y precipitates. In order to make indentation in individual phases in this 
menü 1 work, applied force had to be limited up to 300 uN, because the scale of microstructural features 
her sil A before heat treatment is very fine (interlamellar spacing ) ~ 0.6 pm and rod diameter d < 1pm). : 
due fo Figures 1-3 show three dimensional AFM images of indents used to determine nanohardness 
ue Stability and Young’s modulus. Indentations in as-cast lamellar and rod-like eutectic are shown on Figs. 1 
‚A Scale of the and 2 respectively. Application of the same force has produced smaller indents in -phase lamellae, 
A. praes, hae than in p-phase lamellae (Fig. 1), which is an indication of greater hardness. Also, after indentations 
in o-phase lamellae, small volume of -phase was piled-up on the surface close to the indentation, 
Vr while the surface of phase showed no significant pile-up behavior (Fig. 1). Fig 3 a-c shows 
E den i indentations in alloy after heat treatment. It can be observed that rods of RuAl phase are coarser and 
om he ld that the characteristic pile-up volume in the o-Ru phase is also created like in the as-cast samples. 
dv ie effect of That means that the formation of piled-up volume is not the result of the influence of neighboring 
oy I RuAl lamellar phase, but the intrinsic property of y-Ru phase. 
Surface profiles obtained by AFM, clearly illustrate the ability of o and g phase to 
accommodate deformation. Piled-up volume near indentations in o phase (Fig.3a), indicate the 
plastic anisotropy of this phase and poor ability to accommodate deformation. On the other hand, ß 
/ purity starting phase is readily deformed, leaving no piled-up volume after indentation (Fig.3c), which is 
alloy was heat consistent with observations of Lu and Pollock [8]. Investigating different RuAl alloys, Lu and 
observed in 2S- Pollock concluded, that the deformation kinetics and dislocation substructure suggest high intrinsic 
cd suspension). deformability for RuAl alloys with the respect to other high temperature B2 aluminides. After trace 
a Digi analysis of transmission electron micrographs, these authors reported that possible slip systems are 
ed Berkovich {110} <110> and {011}<100>, suggesting that five independent slip systems may be available for 
: was used for deformation in RuAl. 
wl fi Young’s modulus is a measure of the stiffness of the material and is the most structure 
mela 08 insensitive of the mechanical properties. It is strongly dependent on the binding forces between 
oT atoms and is, generally, slightly affected by alloying, heat treatment and cold work [9]. Fig.4 shows 
wt me Young's modulus of different microstructural features before and after heat treatment determined 
he Posson 5 69 with the applied force of 200 and 300 uN. Indentations with the force of 200 uN yielded values of 
vd Inden fu“ Young’s modulus somewhat smaller, than with the force of 300 uN (maximum difference 25 GPa). 
In as-cast specimen E modulus decreases in the following sequence in RuAl phase: E | >E was 
Ze gendrites and in -Ru phase: E nos 7 E jamellae” When RuAl and -Ru lamellae are compared, 
RuAl lamellae have moderately (5 %) higher modulus. After homogenization Young’s modulus 
decreased and the aforementioned sequence is retained. 
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