Manufacturing of Cu-Sn foams through SDP

ABSTRACT 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 74µm. 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 σ vs strain ε indicated σmax 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 σmax 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 σmax 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.