Abstract
The influence of the applied pressure and electrical parameters on the macrostructure of specimens consolidated by the medium-frequency electrical resistance sintering technique (MF-ERS) is analysed in this work. This technique is based on the application of pressure to a mass of conductive powder that, simultaneously, is being crossed by a high intensity and low voltage electric current. The simultaneous action of the pressure and the heat released by the Joule effect causes the densification and consolidation of the powder mass in a very short time. The effect of the current intensity and heating time on the global porosity, the porosity distribution, and the microhardness of sintered compacts is studied for two applied pressures (100 and 150 MPa). For the different experiments of electrical consolidation, a commercially available pure iron powder was chosen. For comparison purposes, the properties of the compacts consolidated by MF-ERS are compared with the results obtained by the conventional powder metallurgy route (cold pressing and furnace sintering). Results show that, as expected, higher current intensities and dwelling times, as well as higher pressures and the consolidation of compacts with lower aspects ratios, produce denser materials.
Highlights
The use of electricity as a direct method for sintering metallic and nonmetallic powders was suggested many times in the 20th century and is still a topic of extraordinary interest
Some years later came the studies by Taylor [2] and Lenel [3], who called this technique electrical resistance sintering under pressure (ERS)
It would be desirable to predict the temperature at the contact compact/wafer, being possible to increase the severity of the working conditions and the densification, at the time that avoiding the weld between compact and wafers
Summary
The use of electricity as a direct method for sintering metallic and nonmetallic powders was suggested many times in the 20th century and is still a topic of extraordinary interest. Some years later came the studies by Taylor [2] (in 1933) and Lenel [3] (in the 1950s), who called this technique electrical resistance sintering under pressure (ERS). Many international researchers study different modalities of field assisted sintering techniques (FAST), which is the common name used for these powder metallurgy (PM) electrical consolidation techniques. During this long period, many FAST variants have been developed, with the general final objective of their use on the industrial scale (see Grasso et al [12], Orrù et al [13], and Olevsky et al [14])
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