Influence of Al additions on the reactive synthesis of MoSi2

The modification MoSi2 with Al aids the reactive processing of molybdenum-alumino-silicides. This study has shown that: 1) Addition of Al promotes the formation of a transient liquid phase during reactive processing of MoSi2. 2) The reaction sequence is dependent on factors which effect solid-state diffusion prior to the reaction initiation temperature. Those factors which promote solid-state diffusion between Al and Si will result in the formation of an Al-Si eutectic liquid at 577°C. If solid state diffusion is impeded the liquid formation does not occur until the melting point of Al (i.e., 660°C) is reached. 3) The formation of the transient liquid phase enhances diffusion and lowers the reaction initiation temperature for the Mo(Si,Al)2 alloys relative to monolithic MoSi2. The transient liquid also enhances densification, resulting in low processing temperatures, pressures, and times required for consolidation, as evidenced by the 90% dense Mo(Si,Al)2 alloy reactively hot-pressed at 850°C and 30 MPa for 15 minutes.