Manufacturing of Cu-Sn foams through SDP

Resumo

This work reports the processing of bronze foams manufactured by using the powder metallurgy method
known as Sintering Dissolution Process. During the sintering step, a device with controlled atmosphere separated
from the heating furnace was employed to avoid the quick oxidation of metal particles. The device
allows to control its internal atmosphere with an inert gas avoiding the employment of a controlled atmosphere
furnace (a furnace of this kind incorporates the heating and the control atmosphere systems itself). The
metal used for the present study was bronze powders with a composition of 85%Cu–15%Sn, 8.7g/cm3 in
density, and particle size of 74m. Spherical carbamide (CH4N2O) with particle size of 1mm was chosen as
Space Holder Particles (SHP). The maximum porosity Pf and minimum density ρf values were 42.8% and
3.61g/cm3, respectively. As the carbamide content is increased, the bronze powders content is diminished and
consequently Pf is increased and ρf is diminished, as it would logically be expected. The minimum obtained ρf
value corresponds only to 41.4 % of the bronze density (8.7g/cm3). On the other hand, the plots of stress 
vs strain  indicated max values between 26.86 and 8.45 MPa (20 and 35%vol. of carbamide, respectively).
These obtained values indicate a good metallurgical bond among particles, caused by the uniaxial compression
step and sintering at the correct Ts, previously determined (580ºC). The max decreases as the SHP content
increases, which is due to a significant amount of porosity generated by the SHP dissolution and by the
inclusion of void spaces among the metal particles; the both of them imply a lower area supporting the load,
and consequently a reduction in max value for the samples. The results are interpreted in terms of increase
and decrease of the carbamide and the bronze powder content in the sample, respectively.
Keywords: Bronze foams, sintering dissolution process, cellular metals, metal foams.