CRYSTALLINE-TO-AMORPHOUS PHASE-TRANSFORMATION IN MECHANICALLY ALLOYEDFE50W50 POWDERS

A mechanical alloying process via a ball milling technique has been ap plied for preparing amorphous Fe50W50 alloy powders. The results have shown that during the first and second stages of milling (0 to 360 ks) W atoms emigrate to Fe lattices to form nanocrystalline b.c.c. Fe-W s olid solution, with a grain size of about 7 nm in diameter. After 720 ks of the milling time, this solid solution was transformed to an amor phous Fe-W alloy coexisting with the residual fraction of the unproces sed W powders. During the last stage of milling (720 to 1440 ks) all o f this residual W powder reacts with the amorphous phase to form a hom ogeneous Fe50W50 amorphous alloy. The crystallization temperature and the enthalpy change of crystallization of amorphous Fe50W50 powders mi lled for 1440 ks were measured to be 860 K and -9kJ/mol, respectively. The amorphous Fe50W50 powder produced is almost paramagnetic at room temperature. The powder comprises homogeneous and smooth spheres with an average size of about 0.5 mu m in diameter. Copyright (C) 1997 Acta Metallurgica Inc.