Investment casting is one of the common methods to producing metal foam [1-2]. In this research, the relationship between the strength and porosity and also the effect of the heat treatment on the strength of the C95500 bronze foam was investigated.

For this purpose, first porous samples with Kelvin pattern [3-4] with three types of porosity include of 80, 85 and 90% were designed. Then the designed regular open cell patterns were produced via 3D printer method with a polymer made of PLA. Finally, the printed samples were produced via investment casting method in the dimensions of 2×2×2 cm3.

To investigate the effect of heat treatment on the strength of bronze foams, the following operation heat treatment cycles were performed on the samples:

- The first cycle heating at 900 °C for 2 hours and quenching in water.

- The second heating cycle at 590 °C for 1 hour and then quenching in air.

As it was shown in figure 1, a relatively linear increase in the strength of metal foams with the decrease of porosity was found.

The lowest strength of the plateau stress was for the sample with the 90% porosity (4.42 MPa) and the highest one was for the sample with 80% porosity (15.65 MPa). It is because of more cell wall thickness in the samples with lowest porosity [5-6]. Also, the amount of the strain in the breaking stress point was almost the same for all samples. This indicates that changes in the amount of porosity have a more effect on the strength of the metal foams produced in this method.

The effect of the heat treatment on all samples was also determined. By performing heat treatment, the strength of sampels were increased about 5 MPa and the ductility of them were almost constant. It is also determind that in the sample with the lowest porosity (80%), heat treatment has led to the ridged the stress-strain curve behavior in the plastic region. This indicates brittle behavior in the foam samples produced with low porosity. In fact, in the samples with low porosity, as the cell wall of the foam metal produced increases, the effect of the heat treatment is greater and led to the the brittle behavior.