Processing conditions, microstructure and mechanical properties of hetero-nanostructured ODS FeAl alloys produced by spark plasma sintering

Spark plasma sintering (SPS) has been used to sinter a milled oxide dispersion-strengthened (ODS) FeAl powder in order to prepare dense nanostructured parts. The effect of processing conditions including sintering temperature, holding time and degassing treatments on the microstructure and mechanical properties of the as-sintered materials was investigated. A hetero-nanostructure that contains nano, ultrafine and micrometric grains was confirmed to be developed whatever the processing window, due to the large temperature difference generated during the SPS process itself. The grain size distribution can be tailored by selecting a combination of sintering temperature and holding time while retaining a full densification, which shows the elaboration flexibility of this SPS processing. Increase of the global hardness by reducing average grain size down to the sub-micrometer scale is straightforward. However, the ductility although improved after pre and in-situ degassing treatments is determined by the sample imperfections such as low inter-particle bonding and high oxygen content.