MECHANICAL ALLOYING PROCESSING AND RAPID PLASMA ACTIVATED SINTERING CONSOLIDATION OF NANOCRYSTALLINE IRON-ALUMINIDES

Mechanical alloying (MA) has been used to produce the Fe3Al intermetal lic 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 ef fectiveness of these two milling processes on alloying and grain refin ement were compared. The MA powders were consolidated by a plasma acti vated sintering (PAS) process. The microstructural evolution was chara cterized and evaluated for both the starting MA powders and PAS consol idated specimens by X-ray diffraction, scanning and transmission elect ron microscopy, differential thermal analyzer and atomic force microsc opy. The microstructural refinement during MA processing in the Spex m illed powders resulted in complete alloying of the initial elemental F e and Al powders into a nanocrystalline solid solution after 20 h. A d ifference in densification behavior was observed for the Spex milled p owder compared with attritor milled powders.