The microstructures and
Vickers hardness at room temperature of arc-melting processed intermetallics of
Mo_5Si_3-MoSi_2
hypoeutectic alloy and hypereutectic alloy annealed at 1200℃ for different time were investigated. Lamellar
structure consisted of Mo_5Si_3 (D8m) phase and MoSi_2 (Cll_b) phase was observed in all the alloys. For Mo_5Si_3-MoSi_2
hypoeutectic alloy, the
lamellar structure was found only for annealing and developed well with fine spacing on the order
of hundred nanometers after annaling at 1200℃ for 48h. But when the annealing time was up to 96h, the well-developed
lamellar structure was destroyed. For Mo_5Si_3-MoSi_2 hypereutectic alloy, the lamellar structure was found both before and
afte annealing. However the volume fraction and spacing of the lamellar structure did not change significantly before and
after annealing. The effects of the formation, development and destruction of lamellar structure on
Vickers hardness of al-
loys were also investigated. When Mo_5Si_3-MoSi_2 hypoeutectic alloy annealed at 1200℃ for 48h, the Vickers hardness was
improved about 19% compared with that without annealing and formation of lamellar structure. The highest Vickers hard-
ness of Mo_5Si_3-MoSi_2 hypereutectic was increasing about 18% when annealing at 1200℃ for 48h.