NANOGRAINED SIZE PURE IRON ELABORATED BY MEANS OF SPARK PLASMA SINTERING

摘要

In this study, Spark Plasma Sintering has been used to sinter pure iron with an initial crystallite size around 100 nm. The process parameters for sintering pure iron have been optimized in order to obtain fully dense materials and avoid excessive grain growth. Archimede's method has been used to calculate the relative density of the sintered samples. It appears that almost fully dense materials can be obtained (95%). X Ray diffraction applied to the sintered samples shows the presence of iron and of the wustite oxide FeO (around 6% wt) formed during the sintering process. Peak enlargement measurements show that the grain size after sintering is around 200nm. This is confirmed by TEM observations showing a dual distribution of grain size. Finally, mechanical characterization has been carried out. The sintered compact exhibits a very high hardness of about 400 Hv. Compression test reveals a very high maximal stress of about 1.2 GPa and that the ductility in compression is non negligible. Using the Hall and Petch law, the calculated grain size should be around 450 nm which is in accordance with direct observations.