Prakt. Met. Sonderband 46 (2014) 337 
of SEM and R35.25 
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the influence foo 
cause higher — 7 NN - 
same crack nm 73 12 
n field during TO = 
1 super alloy 
0 0.25 um. 
vth of several 
vitates of the 
cause a very 
able for good 
9 Fig. 1: specimen geometry and configuration of stage-I-crack (crack side B), RO! with 
1} slip planes magnification (magnification reference Polaroid 545) and loading direction (left hand side) 
e slip system and outline of implementation of investigation steps (right hand side) 
r notch was 
‘ormation can 
a cross about 2.2 CRACK INITIATION AND CRACK GROWTH 
upport crack The specimen was loaded ex situ with a stress ratio of R = -0.1 and a stress range of 600 
MPa. Replica were taken every 2000 cycles to observe the crack growth rates and to 
detect when the crack tips reach the ROIs. A da/dN-curve was collected according to 
ASTM E647-13 by 7-point smoothening (Fig. 2). 
1,00£-05 
module. The 54k 
her than the _ | 
ne rearrange Y * ++ N 
e dislocation *1,00E-06 5 $ sok 695 
igh the crack 
* 
e exactly the 3 
ns alignment 
st achievable 1,00E-07 de 
Zeiss Sigma 2 OK, [MPavm] 4 
La maximum Fig. 2: da/dN-curve: the cycle numbers for image collection were marked 
at the stress 
ess gradient 2.3 MEASUREMENT IMAGES 
ie ROI with a 
The measurement images (Fig. 3b) were achieved from 54000 up to 78000 load cycles 
region of an with exactly the same SEM beam and detector parameters as the reference images. 
was in good Special attention was dedicated to the exact repositioning of the specimen in the in situ 
tensile module and the SEM to avoid translation and rotation artefacts in the image 
correlation analysis.