F. RADKOVSKÝ, V. MERTA: PRODUCTION OF CAST POROUS METAL
139–141
PRODUCTION OF CAST POROUS METAL
IZDELAVA POROZNIH KOVINSKIH ULITKOV
Filip Radkovský, Václav Merta
VSB – Technical University of Ostrava, Faculty of Materials Science and Technology, Department of Metallurgy and Foundry Engineering, 17.
listopadu 15/2172, 708 33 Ostrava–Poruba, Czech Republic
Prejem rokopisa – received: 2018-07-13; sprejem za objavo – accepted for publication: 2018-10-18
doi:10.17222/mit.2018.146
The article deals with the foundry methods of manufacturing porous metal; it is focused on the materials with a regular
arrangement of internal cells. Currently, there are many fields dealing with the problem of porous metals by either optimizing
the already known technologies, developing new ones or using porous metals. The production of a porous metal with a regular
structure of cells and the possibility of its functional usage are the main subjects of this article. Due to their shapes, sizes and
distribution of internal pores, cast porous metals exhibit various properties including reduced weight, sufficient strength, an
ability to absorb impact energy, a possibility to conduct heat, etc., that allow a wide range of applications in the areas such as
construction, transport or power engineering.
Keywords: porous metal, energy absorption, lost foam, deformation work
^lanek opisuje livarske metode izdelave poroznih kovin. Osredoto~a se na materiale s pravilno urejenostjo notranjih celic.
Trenutno se na mnogih podro~jih ukvarjajo s problemi poroznih kovin, bodisi z optimizacijo `e znanih tehnologij, razvojem
novih, ali njihovo uporabo. Glavni predmet ~lanka je izdelava poroznih kovin s pravilno strukturo celic in mo`nostjo njihove
uporabe. Porozni ulitki imajo zaradi svoje zna~ilne oblike, velikosti in porazdelitve por razli~ne specifi~ne lastnosti, vklju~no z
manj{o maso, zadovoljivo trdnostjo, sposobnostjo absorpcije udarne energije, prevajanja toplote itd. Vse to omogo~a njihovo
uporabo na razli~nih podro~jih, kot so konstrukcije, transport, in`eniring prenosa energije in mo~i.
Klju~ne besede: porozne kovine, absorpcijska energija, ulivanje z izparljivimi modeli, deformacija
1 INTRODUCTION
The term of porous metal refers to a light, porous
material with a cellular structure but with good mecha-
nical properties. The porosity of these materials, i.e., the
ratio of the vacant space to the total volume, ranges from
75 % to 95 %. Cavities can be connected with open
pores; in this case, the material is a porous metal with
open cells. Cavities can also be mutually separated and
then the material is a porous metal with closed cells.
1,2
1.1 Use of porous metals
Metal foams find many applications in many
industrial sectors (transport, aviation, defence, marine
industry, power engineering and architecture). Foams are
used as multifunctional materials for high-performance
applications for civil, mechanical, chemical and
biomedical engineering.
3
Due to their low weight, high
strength and the ability to absorb energy, porous-metal
materials are suitable for the use, for example, in the
deformation zones of conveying devices.
4,5
1.2 Method of production
A variety of methods and techniques for the pro-
duction of porous-metal materials can be found in
practice. The production involving conventional casting
processes used in foundries ensures an economic manu-
facture without the need to acquire expensive equipment.
For the production of porous materials, the method of
pouring a solid filler material with a liquid metal can be
used as an example. After removing the filler material,
the pores become structured. The size and shape of these
castings are defined on the basis of the properties, at
given process repeatability and in compliance with the
process and production conditions.
6
The defined
properties of these modern materials are crucial for the
other applications.
7
2 EXPERIMENTAL PART
The experiment was focused on the production of
metal foams with a regular structure and the testing of
their mechanical properties. For the production of
samples, the lost-foam method, i.e., the investment
casting process was used. This is a widely used method
for the manufacture of precision castings. For the manu-
facture of the pattern, expanded polystyrene (EPS) was
used as a material suitable for the lost-foam method and
also as a material fairly flexible for the manual manu-
facture of the pattern. The dimensions of the grids were
(52 × 52 × 6) mm and the overall dimensions of the
pattern were (52 × 52 × 42) mm. The pattern consisted of
Materiali in tehnologije / Materials and technology 53 (2019) 1, 139–141 139
UDK 669.1:546.3:621.747:539.217 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 53(1)139(2019)
*Corresponding author e-mail:
filip.radkovsky@vsb.cz

seven floors/grids that were glued together and equipped
with a grating system.
The pattern together with the grating system was
dipped in a fireproof coating of the FOUNDRYLAC
ZBM/365 type. The cast material was aluminium alloy
AlSi11, which is suitable for the production of thin-
walled and shape-complicated castings. The alloy was
molten in an electric resistance furnace (LAC 80/13). For
a better alloy fluidity, higher casting temperatures were
chosen, e.g., 750 °C. The molten metal was poured
directly on the pattern, which was placed in a flask and
filled with dry quartz-based sand without a binder and
compacted with vibration. The casting of the porous
metal with the grating system is shown in Figure 1a.
3 RESULTS
All the samples with the dimensions of (52 × 52 ×
42) mm were subjected to a pressure test. A total of 20
porous-metal samples with a regular structure were
tested. The tests were carried out at company VÍTKO-
VICE TESTING CENTER s.r.o. (Ltd.), a member of the
VÍTKOVICE MACHINERY GROUP. Pressure tests
were carried out on a Zwick Z600 machine with an
advancing speed of 10 mm/min. A sample before and
after the pressure test is shown in Figures 1b and 1c.
The castings manufactured with the lost-foam me-
thod were tested to investigate the material performance
at constant loading and different deformation curves
were determined. Several dozens of samples were
measured. Selected values obtained with the pressure
tests are given in Table 1. Using the calculations of
triangles and cuboids for the potential, deformation
curves (the area under a curve) and the values of the
strain energy, i.e., deformation work (J) were calculated.
4 DISCUSSION
It is clear from the results of the pressure tests that
Sample no. 8 reached the highest compression strength
(354 kN) and, at the same time, it exhibited the highest
deformation (31.7 mm). The highest values of deforma-
tion were found for sample no. 13 (3872 J); its com-
pression strength was slightly above the average of all
the samples. The average of the maximum com-
pression-strength values for the tested samples was
272.50 kN. Deformation curves for different samples
showed a similar trend and for this reason, only the
F. RADKOVSKÝ, V. MERTA: PRODUCTION OF CAST POROUS METAL
140 Materiali in tehnologije / Materials and technology 53 (2019) 1, 139–141
Table 1: Results of the pressure tests of individual samples
Sample number
Casting temperature
(°C)
Real dimensions after
machining (mm)
Max. compression
strength (kN)
Max. deformation
(mm)
Deformation work
(J)
1 793 49.7 × 49.3 × 38.3 254 29.1 2962
5 792 49.3 × 49.6 × 38.3 276 28.9 3027
7 807 49.8 × 49.0 × 38.0 277 30.6 2831
8 807 49.7 × 48.8 × 38.4 354 31.7 3340
9 795 48.8 × 48.0 × 38.4 268 29.1 3010
13 807 48.0 × 48.8 × 38.4 283 28.8 3872
16 807 49.4 × 48.3 × 38.6 325 29.9 3486
19 808 48.5 × 49.5 × 38.2 270 27.7 3205
Figure 2: Force vs. stress curve
Figure 1: a) casting, b) machined sample, c) compressed sample

graph for sample no. 13 is shown as a representative
example, Figure 2.
5 CONCLUSIONS
The dimensions of (52 × 52 × 42) mm were chosen
for the polystyrene pattern. These samples were pressure
tested. The average value of the maximum compression
strength was 272.50 kN. Individual values of the strain
energy were calculated for the total areas under
individual deformation curves. The average value of the
strain energy was 3150 J. Due to the obtained values of
the strain energy, this porous metal can be recommended
for further development with respect to applications in
transportation deformation zones. The potential of this
modern material to absorb a large amount of impact
energy is obvious from the obtained results, but it is still
difficult to find the right shape for a specific application.
Acknowledgment
The contribution was carried out with the support of
the Technology Agency of the Czech Republic –
TH02020668, TA02011333 and project of "Student
Grant Competition" numbers SP2019/148 and
SP2019/43.
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