Abstract

Milling media of steel and partially stabilized zirconia(PSZ) were used to produce Mo_3Si by mechanical alloying(MA) of Mo-25.0at%Si elemental powder mixture. The effect of milling medium materials on MA of the powder mixture have been investigated by XRD and DTA. The reaction rate and the end-product noticeably depended upon the milling medium material. The formation of Mo_3Si and Mo_5Si_3phases by PSZ ball-milling took place after 15 hr of MA and was characterized by a slow reaction rate as Mo, Si, Mo_5Si_3 and Mo_3Si coexisted for a long period of milling time. The formation of a new phase by steel ball-milling, however, did not take Place even after 96 hr of MA. DTA and annealing results showed that Mo_5Si_3 and Mo_3Si were formed after heating the ball-milled powder specimens to different temperatures. At low temperatures, Mo and Si were transformed into Mo_5Si_3. At high temperatures, the formation of Mo_3Si can be partially attributed to the reaction, 7Mo+Si+Mo_5Si_3-.4Mo_3Si . The formation of Mo_3Si and Mo5Si3 phases by mechanical alloying of the powder mixture and the relevant reaction rate appeared to depend upon the milling medium material as well as the thermodynamic properties of the end-products.