132 Prakt. Met. Sonderband 38 (2006) 
‘ 40 60 80 100 120 140 160 
Length (um) 
Figure 4: Object 1: Extraction of the COD; value from the profile marked in Fig. 2. The 
dashed profile corresponds to surface S2 the solid profile to surface S1. 
Figure 5: (a) Difference height map between surfaces S2 and S1 of the cast MMS (object 
1). (b) Difference height map between surfaces S1 and S2 of object 2. Grey corresponds 
to regions with good correspondence. white to void areas and black to regions with e 
material overlap. 
Two SEM images from the powder-metallurgy MMC are presented in Fig. 6. After the 
reconstruction of both 3D models but before the automatic registration algorithm has been t 
applied, several corresponding profiles of the broken halves have been manually analyzed r 
and drawn into the images. The path of one of these profile pairs is marked in Fig. 6. The 
corresponding fracture surface profiles are depicted in Fig. 7a. Figure 7b shows the ' 
corresponding fracture surface profiles which have been determined after the automatic ; 
registration. In contrast to the manually segmented profiles, the algorithm seems to 
account better for translations and rotations between the two 3D models and was able to 
find the correct corresponding profile. 
The misfit map of the powder-metallurgy MMC is shown in Fig. 5b. In contrast to the cast . 
MMC, this specimen fractures without significant plastic deformations. For the object which . 
has a total maximum height of about 650 um, the difference between the registered height 
models is below +10 um for large parts of the model (grey). There are only small void 
areas (white) with differences up to about 50 ym and a few regions with larger surface 
overlap (dark) with differences up to 150 pm. In most cases, the areas with large misfit are 
very narrow, occurring at positions of steep or vertical slopes in the model. The misfit 
would probably disappear if one 3D model were only slightly shifted. Since in general the 
misfit is small, the pre-crack front cannot be determined as easily as for the cast MMC.