Synthesis and characterization of mechanically alloyed Nb3Al-base alloys

Two Nb–Al alloys containing 18 and 20 at.%Al were successfully processed by mechanical alloying followed by hot pressing. Analysis of X-ray spectra as well as transmission electron microscopy studies revealed the presence of four phases: niobium solid solution (Nbss), Nb3Al, Nb2Al and dispersoids of Al2O3. The grain size was estimated to be approximately 1 μm. Nbss grains contained a very high dislocation density while a high density of planar stacking faults was observed in the intermetallic phases. The alloys exhibited only limited compressive ductility at room temperature but were ductile at 1000°C. The mechanism for creep deformation in the examined Nb–Al alloys is postulated to be dislocation creep through diffusion controlled climb. The compressive strength was higher and creep rates were lower in the present materials compared to reference NiAl-based materials processed and consolidated using the same techniques.