Clee 300 uN EEE Homogenized 300 UN ? L__"]As-cast 300uN limll Homogenized 300uN Results &
400 | EX As-cast 200 uN [TTTf Homogenized 200 uN 77] As-cast 200uN [[iT]Homogenized 200uN
350 - 20
3 300 |} |} x desıred \
x Ts
© 250 -
3 i
5 200 : u
5 A 5
2 150
w
100
50- order 10
oH . properlie
RuAlLamellae RuAlrods RuAldendrites Ru lamellae RE RuAl _amellae RuAlrods RuAldendrites Ru lan sax Tawa i,
Microstructural features Microstructural features Ae en
Fig. 4. Young’s modulus of different phases. Fig. 5. Nanohardness of diferent phases. prev
resulted
. work, al
The o-Ru solid solution (hcp) is known to be extraordinarily brittle at room temperature [5]. before h
On the Ru rich side ( 53 = 95 at.% Ru ) of the Ru-Al system, RuAl (ß phase), together with o-Ru,
forms an eutectic (op; T _~1920°C). This eutectic, as a specific composite material, due to
synergism effect of individual phases, their fineness, morphology and thermodynamic stability, and You
could be exploited as structural or functional material at elevated temperatures. The scale of the and
microstructural features is very fine, therefore, the mechanical properties of individual phases, have thar i=:
to be determined in the range smaller than micrometer. in ld
A nanoindenting atomic force microscope, which allows measurements of the local rn
mechanical properties with lateral resolution of nearly 50 nm, was used to determine the forte
nanohardness and the Young’s modulus. These mechanical properties are calculated from the load- os
displacement curves recorded during indentations. The aim of this work is to study the effect of _
morphology and heat treatment on local mechanical properties of existing phases in Ru-Al eutectic. Res
Experimental Se
An alloy with nominal composition Ru, Al, at. % was prepared from high purity starting phase
materials by vacuum arc melting in protective argon atmosphere. After melting, the alloy was heat {Ona
treated (homogenized) at 1300°C for 100 hours in argon. Produced samples were observed in as- Pollocl
polished condition (final step of polishing was done with 0.05 um diamond suspension). deform
Nanohardness (NH), and Young’s modulus (E), were determined using the AFM (Digital analysı
Instruments) combined with Hysitron nanoindenter system, equipped with three sided Berkovich NI
indenter, previously calibrated for the applied load. The same AFM tip, which was used for deform
indentation (loads 200 and 300 uN), was subsequently used to scan the surface. Local mechanical
properties of different microstructural features (-Ru lamellae and hallos and p-RuAl lamellae, rods
and primary dendrites) before and after heat treatment, are estimated from the load-displacement eens
curves using the method of Oliver and Pharr [6]. Young’s modulus is calculated after estimation of SE:
the slope of the load-displacement curves in the unloading part, taking into account the Poisson’s co- Co
efficients of RuAl (yp, ,, = 0.286 [1]), pure ruthenium (yp, = 0.25 [7]), and diamond indenter (y, = bo
0.07 [6]) and Young’s modulus of the diamond indenter (E_ = 1141 GPa [6]).
104
