X-ray diffraction study of solid-state formation of metastable MoSi2 and TiSi2 during mechanical alloying

The formation of metastable C40–MoSi2 and C49–TiSi2 during the mechanical alloying of metal/silicon powder mixtures has been investigated by x-ray diffraction. The mechanical alloying of a Si-rich Mo/Si powder mixture results in the formation of both C11b–MoSi2 and C40–MoSi2. The C40–MoSi2 phase is metastable and transforms to C11b–MoSi2 after annealing at 850 °C. The mechanical alloying of a stoichiometric Ti/Si powder mixture leads to the incipient formation of C49–TiSi2 and the subsequent polymorphic transformation to C54–TiSi2. The lattice parameters of C49–TiSi2, as determined from a mechanically alloyed Ti/Si powder sample that has been annealed at 700 °C, are as follows: a0=3.56 A, b0=13.57 A, and c0=3.55 A.