High-temperature stability of nano-grained B2-structured RuAl-based intermetallics by mechanical alloying

A series of nano-grained B2-structured RuAl-based intermetallics and corresponding composites are synthesized by mechanical alloying. These RuAl-based materials include stoichiometric RuAl, B2-structured ternary (Ru,Ni)Al and (Ru,Ir)Al, eutectic RuAl-Ru and particle reinforced RuAl-ZrO2 composite. The accumulation of impurities, mainly Fe, in grain boundaries and the structural evolution during grain growth are found to be the controlling factors for the grain growth stagnation in nano-grained B2-structured binary RuAl and ternary (Ru,Ni)Al and (Ru,Ir)Al intermetallics. Ternary alloying element forming iso-structured pseudo-binary compounds, eutectic in situ and ceramic particle reinforced composites are explored to be the effective routes to enhance the stability of single-phase RuAl. The thermal stability of microstructure in various RuAl-based materials are found to decrease in a sequence from pseudo-binary RuAl-IrAl, RuAl-NiAl, eutectic RuAl-Ru composites, ceramic particle reinforced RuAl-ZrO2 composites to binary stoichiometric RuAl.