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Materials Science in Additive Manufacturing Measuring the porosity of AM components

completely isolated from other pores (Figure 1A). These 2.2. Determination of material density and porosity
pores influence the macroscopic properties of bulk density, When considering a component with or without its closed
elasticity, mechanical strength, and thermal conductivity pores, there are differences in terms of density and porosity.
of a part. 18,20 Open pores, on the other hand, have either Apparent density is referred to when the total volume
one opening (blind pores) or several openings (continuous of a component including all (open and closed) pores is
pores) or connections to the outer component surface considered (Figure 2, left). The apparent density is calculated
(Figure 1B-D) and enable exchange with the environment by dividing the part mass by the total volume (including
through media flow. 18,20 In the case of pores, it should the pores). If the pores are not considered when measuring
also be noted that, by definition according to ISO 15901- the density, this is referred to as the true density (Figure 2,
1, they must also be deeper than wide to be categorized right). It is calculated by dividing the part mass by the part
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as pores. Otherwise, according to Klobes and Munro, volume without pores. The difference between apparent and
corresponding areas are more likely to be categorized as true density indicates the porosity of the material.
surface roughness (Figure 1E).
There are different measurement methods for measuring
the individual types of density. Gravimetric density
measurement according to Archimedes’ principle includes
the trapped air in the component and is therefore very suitable
for apparent density, while, for example, gas pycnometry
largely displaces the trapped air from the component and
is therefore more suitable for determining true density. This
is due to various properties such as the existing pore size,
the structure of the pores, and the material density, which
influence the reliability of a measurement. Figure 3 shows
further measurement methods that characterize certain
pore sizes and provide conclusions about the part density
and part porosity. Table 2 then describes the advantages and
disadvantages of the individual methods with regard to the
Figure 2. Difference between apparent and true density determination of part density and porosity.

Figure 3. Limits of different pore size measurement methods (according to Klobes et al. )
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Volume 4 Issue 2 (2025) 4 doi: 10.36922/MSAM025090010