Effect of the method of introduction of Y2O3 into NiAl-based powder alloys on their structure: I. Agitation in a ball mill

The effect of the sintering temperature (1100–1400°C) of NiAl alloy samples with oxide Y 2 O 3 produced by hydrostatic pressing on their structure and phase composition and the distribution of oxide particles in a NiAl-based intermetallic matrix alloyed with ∼0.5 at % Fe is considered. It is found that dispersed oxide particles in the compact material prepared from a mixture of oxide Y 2 O 3 powder and a NiAl alloy (produced by calcium hydride reduction of a mixture of nickel and aluminum oxides) powder in a standard ball mill are nonuniformly distributed in the volume. The morphology of oxides changes during sintering: sintered samples contain rounded particles, which differ strongly from the clearly faceted angular particles of oxide Y 2 O 3 added to a mixture (they represent conglomerates of single crystals). In the sintered samples, large aggregates of oxides are revealed along grain boundaries. Mass transfer is possible at the NiAl/Y 2 O 3 interface in the system: it leads to partial substitution of aluminum and/or iron atoms for yttrium atoms in the Y 2 O 3 lattice and to the formation of submicroscopic particles of (Fe,Al) 5 Y 3 O 12 -type oxides.