Mechanical alloying of MoSi 2 with ternary alloying elements. Part 2 computer simulation

Abstract

A computer model of the mechanical alloying process has been developed to simulate phase formation during the mechanical alloying of Mo and Si elemental powders with a ternary addition of Al, Mg, Ti or Zr. Using the Arhennius equation, the model balances the formation rates of the competing reactions that are observed during milling. These reactions include the formation of tetragonal C11 b MoSi 2 ( t-MoSi 2) by combustion, the formation of the hexagonal C40 MoSi 2 polymorph ( h-MoSi 2), the transformation of the tetragonal to the hexagonal form, and the recovery of t-MoSi 2 from h-MoSi 2 and deformed t-MoSi 2. The addition of the ternary additions changes the free energy of formation of the associated MoSi 2 alloys, i.e. Mo(Si, Al) 2, Mo(Mg, Al) 2, (Mo, Ti)Si 2, (Mo, Zr)Si 2 and (Mo, Fe)Si 2, respectively. Variation of the energy of formation alone is sufficient for the simulation to accurately model the observed phase formation.