Phase formation during annealing as-milled powders of molybdenum disilicide

Molybdenum disilicide was synthesized by mechanical alloying (MA) technique through the elemental powder mixtures. Both alpha-MoSi2 and beta-MoSi2 phases are created at the beginning stage; the final products of the mechanical alloying are beta-MoSi2 phase and amorphous state substance when milled for 96 h. The study also extended to determine the effect of the milling time on the kinetics of the phase transformation during annealing at low temperature. Mo5Si3 is formed and the phase transformation of alpha-MoSi2 to beta-MoSi2 occurred during the annealing at 800 degreesC, meanwhile, the crystallite size of alpha-MoSi2 grows up obviously. MoSi0.65 is formed during annealing for the powders milled for 48 and 96 h, which suggests that MoSi0.65 phase is the predominant phase prior to the MoSi2 during the crystallization of the amorphous substance. The main reaction of the powders milled for 48 and 96 h and annealed at 800 degreesC is the crystallization of the amorphous substance and a trace mounts of the phase transformation of beta-MoSi2 to alpha-MoSi2. (C) 2003 Elsevier Science B.V. All rights reserved.