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 74m. 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.
Highlights
The technology of powder metallurgy (PM) has been highlighted as a source in the making of new materials and light parts providing a reduction of production costs mainly in the automobile industry
The sample presented a regular pores distribution, which results in bronze foams with a highly homogeneous framework, as it is required for reliable measurements of mechanical properties in this kind of material
The minimum obtained ρf value was 3.7 g/cm3, which corresponds to only 42.5% of the bronze density (8.7 g/cm3)
Summary
The technology of powder metallurgy (PM) has been highlighted as a source in the making of new materials and light parts providing a reduction of production costs mainly in the automobile industry. The PM processes have been used to fabricate porous metals These porous metals ( called cellular metals) with high porosity have been developed to use them as new functional materials, given that these materials present a unique combination of physical and chemical properties, which can be derived from their cellular structure [1]. Porous metals show increasing potential for applications in a wide range of structural and functional products, due to their exceptional mechanical, thermal, acoustic, electrical and chemical properties [2,4]. Developed a technique to manufacture open–cell foams at low cost using the PM route, known as the sintering and dissolution process (SDP). The SDP route is employed to fabricate porous bronze (with increasing porosity to obtain closed pore and open pore foams) with regular pore size and good mechanical properties, using bronze powders and carbamide as SHP
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