Mechanical alloying processing and rapid plasma activated sintering consolidation of nanocrystalline iron-aluminides

Mechanical alloying (MA) has been used to produce the Fe3Al intermetallic compound from elemental Fe and Al powders. A high energy Spex 8000 mixer mill as well as a low energy mechanical attritor were used for producing nanocrystalline and/or very fine crystallite powders. The effectiveness of these two milling processes on alloying and grain refinement were compared. The MA powders were consolidated by a plasma activated sintering (PAS) process. The microstructural evolution was characterized and evaluated for both the starting MA powders and PAS consolidated specimens by X-ray diffraction, scanning and transmission electron microscopy, differential thermal analyzer and atomic force microscopy. The microstructural refinement during MA processing in the Spex milled powders resulted in complete alloying of the initial elemental Fe and Al powders into a nanocrystalline solid solution after 20 h. A difference in densification behavior was observed for the Spex milled powder compared with attritor milled powders.