160 Prakt. Met. Sonderband 46 (2014) 
samples were polished again and investigated under an inverted optical microscope 
(Olympus GX51). 
Image analysis: In order to calculate the porosity, the software program Fiji has been 
used. Fiji is an open source image processing program, based on ImageJ. First, the 
picture was converted into a grayscale image, then a threshold was set automatically by 
the program (thresholded pixels are set black; all other pixels are set to white). ‘In the next 
step, an area of the image was calibrated (in um?) and then an area fraction was analyzed 
by the program (edges are excluded), i.e. the program calculates the percentage of all 
black “parts” in the image. 
3. RESULTS AND DISCUSSION Fig. 6 F 
The first sample to be analyzed was the + 
Fe21Cr powder uniaxially compacted and 
then sintered at 1300°C for 60 min in Hz. 
The green density for the sample 
compacted at 100 MPa was measured as 
4.07 g/cm3, the sintered density as 4.60 
g/cm?3 (Archimedes method). The 
pycnometric density of the powder was 
measured as 7.54 g/cm®. The porosity 
(39%) can be seen in Fig. 4, the pores are 
homogeneously distributed, but in part also 
big pores can be seen. These pores result es 
. co 200 um 
from agglomerates of wax while mixing, and STAU na ak 
while dewaxing these agglomerates form F'9- 4: Fe21Cr + 2wt% paraffin wax, 100x, 
voids. Needless to say that these voids can uniaxially pressed at 100 MPa, dewaxed ) 
be detrimental for the mechanical stability and sintered. 39% porosity *This 
of the porous metal support. The linear 
shrinkage of the sample is about 5.4%. 
In Table 
The distribution of the pores of the Fe16Cr ' -— calculate 
MIM sample with 50 vol% powder loading \ separatic 
can be seen in Fig. 5. The distribution is MiCrosco 
very even, without any agglomerations the poro: 
even for this high binder content. Fine same. Fe 
porosity (in total 22%) can be seen in both : impregne 
directions, here only the cross section is samples 
shown. The green density was measured measure 
as 4.32 g/cm®, the sintered as 6.10 g/cm? analyzed 
(Archimedes method). The shrinkage 
during sintering is about 13% and it is : 
isotropic. This is in agreement with the fact oe 4. CON 
nat injector moulding ni is always Fig. 5: Fe16Cr, MIM; vacuum sintered 
aimed to be an Isolropic forming process 43p9°c, 60min), cross section, 26,5% Usually 
unless segregation effects occur. porosit depositic 
y 
gravity : 
characte