Published online by Cambridge University Press: 25 February 2011
The grain growth behavior of polycrystalline MoSi2 and composites containing SiC particulates has been studied in the temperature range of 1200-1800°C during static annealing as well as under concurrent deformation conditions. Monolithic MoSi2, with ∼ 26 μm grain size appears to be extremely resistant to grain growth up to 1500°C. However, the grain growth rate above this temperature is quite rapid. When particulate reinforcements are used to reduce the grain size of MoSi2 to 4.4 μm, a stable microstructure is maintained up to 1500°C. Accelerated grain growth kinetics are observed at 1800°C under conditions of large plastic strain. This enhanced grain boundary mobility is associated with particle sweeping and particle agglomeration effects. At lower temperatures, where dislocation creep is the more dominant deformation mechanism these effects are absent. In the presence of a Si concentration gradient extremely high growth rates of columnar MoSi2 grains have been observed during reaction synthesis of MoSi2.