Microstructure Evolution of Mechanically Alloyed ODS Ferritic Steels during Hot Extrusion

Direct hot extrusion of powder is the standard consolidation process to transform mechanically alloyed Oxide Dispersion Strengthened (ODS) steels into fully dense bars. It is a complex process including several steps. In this study, ODS steel bars were extruded and the material microstructure was characterized by TEM observations associated to SANS after each step. It was shown that the nano-cluster nucleation occurs during the powder pre-heating before hot-extrusion. During extrusion, the ferritic matrix undergoes a dynamic recovery but no further change of the nano-cluster distribution is observed.