Red 19 the 
. te erie Fig. 2a shows microstructurally short fatigue cracks that nucleated at a grain boundary (GB) and are 
vig dong growing transgranularly along slip bands. The short crack shown in Fig. 2b and indicated by an 
arrow initiated intergranularly. The misorientation angles between the grains involved are relatively 
ed SpeCimen is high. 
Anelling contrast 
smears of the 
socally scateeg 
(1) 
acing. The ele- 
sphorous screen 
responds fo the 
tomatclly (Ori 
1 Software) from 
naga ar 4 
Figure 2: Short fatigue cracks on the surface of LCB a) transgranular and b) intergranular 
YL 
The propagation characteristic of the short cracks in Fig 2a are documented in Fig. 3, prepresenting 
Ma Me the development of the crack length between 500 and 3000 cycles. 
Wo Ys 
Wao My 
300 . 
] el ad 
ion S yo! Olowangle [¥ 
GB, oo 
sal direction 200 : b 4 @ triple 
normal point 
' 150 * : 
L00 - A a? 
rienitation of the PEN 
s matrıX element 50 U + © triple 
a bcc crystal aus. A % point 
entation an‘ 9 0 - 7 
study hig-angl® 0 500 1000 1500 2000 2500 3000 3500 20m 
sel descrintions Of a 
number of cycles N 
Figure 3: Influence of misorientation on the short crack growth behaviour (up to 60%Nr) 
sasgramularly %5 ; . . x 
os (0 It can clearly be seen that the short crack propagation behaviour for given loading parameters (Ac/2 
i cee = 600 MPa, f = 1 Hz, R = -1) is hardly influenced by a low-angle GB. The slip band crack b grows 
much faster than the neighboured short cracks and crosses the low-angle GB © without changing 
161