Abstract

Milling media of steel and zirconia were used to produce MoSi_2 by mechanical alloying (MA) of Mo and Si powders. The effect of milling media on MA of Mo-65.8at%Si powder mixture has been investigated by SEM, XRD, DTh and in-situ thermal analysis. The powders mechanically alloyed by milling medium of steel for 8 hours showed the structure of fine mixture of Mo and Si, and those mechanically alloyed by milling medium of zirconia for longer milling time showed the structure of fine mixture of Mo and Si. The tetragonal alpha-MoSi_2 Phase and the tetragonal Mo_5Si_3 phase appeared with small Mo peaks in the powders milled by milling medium of steel for 4 and 8 hours. The alpha-MoSi_2 phase and the hexagonal beta-MoSi_2 phase were formed after longer milling time. The alpha-MoSi_2 phase appeared with large Mo peaks in the powders milled by milling medium of zirconia for 4 hours. The phases, alpha-MoSi_2 and beta-MoSi_2. were formed in the powders milled for longer milling time. DTA and annealing results showed that Mo and Si were transformed into alpha-MoSi_2 and Mo_5Si_3, while beta-MoSi_2 into alpha-MoSi_2. In-situ thermal analysis results demonstrated that there were a sudden temperature rise at 212 min and a gradual increase in temperature in case of milling media of steel and zirconia, respectively. The results indicate that MA can be influenced by materials of milling medium which can give either impact energy on powders or thermal energy accumulated in vial.