Formation of Intermetallic Compound MoSi₂ and Mo₅Si₃ by Mechanical Alloying

Abstract

We applied mechanical alloying to produce molybdenum silicides MoSi₂ and Mo₅Si₃ using a mixture of elemental molybdenum and silicon powders at room temperature. The intermetallic compound MoSi₂ have been obtained by ball milling for 100 h, which is transformed to single phase by subsequent heat treatment up to 725°C. The grain size of the MoSi₂ powder thus obtained was 19 nm, being approximately four times smaller than that of the commercial alloy. The intermetallic compound Mo₅Si₃ have been also obtained by MA for 500 h, which is transformed to single phase by heating up to 1000°C. We believe that the retarded MA time for the formation of Mo₅Si₃ phase is attributed to its complicated crystal structure and large unit cell. The finer grain size in the MA powders is expected to improve room-temperature mechanical properties.