Mechanically alloyed Mo-Si-B alloys with a continuous α-Mo matrix and improved mechanical properties

Mechanical alloying (MA) followed by cold isostatic pressing (CIPing), sintering and hot isostatic pressing (HIPing) was used to prepare Mo-base silicide alloys consisting of a Mo(Si) solid solution and the intermetallic phases Mo3Si and Mo5SiB2. The microstructural development during milling of both binary Mo-Si and Mo-B and ternary Mo-Si-B powder mixtures was evaluated. While obtaining a supersaturated solid solution requires rather long milling times, domain size (which correlates with the grain size) is reduced to below 100 Å after about 10 h of milling. After heat treatment and consolidation the microstructure reveals a continuous α-Mo matrix with embedded, uniformly distributed intermetallic particles. The establishment of such a microstructure is beneficial for the mechanical properties since, as compared to a discontinuous α-Mo matrix, it decreases the brittle-to-ductile transition temperature (BDTT) by about 150 K.