Effects of particle size and pressure on the reactive sintering of RuAl intermetallic compound

Single phase RuAl was synthesized from elemental powders by reactive sintering and reactive hot pressing. Both processes involve a self-propagating exothermic reaction between the constituent powders to form an intermetallic compound. It was shown that particle size ratio and pressure strongly affect the reaction mechanism, structure, and density of the final material. Without pressure, reactive sintered products had a relative density up to 81% of the theoretical and were mainly composed of RuAl with uniformly distributed large pores. Green density has also an effect on densification. The application of pressure before the self-ignition of green compact leads to the formation of a multiphase structure. Molar volume effect between reactants and products, and heat transfer from the specimen after the reaction has taken place are assumed to be the main reasons for the formation of the multiphase structure. Extended homogenization treatment was necessary to drive the reaction to completion and to obtain single-phase microstructure. In addition, homogenization resulted in a relatively high-densified product (relative density as much as 94.4%).