Effects of Ru on microstructure stability and mechanical properties of Ni₃Al single crystal alloy

The effect of Ru on microstructure stability and stress rupture properties of a Ni₃Al single-crystal alloy was investigated. The experimental results showed that the addition of 2% Ru (mass fraction) improved the microstructure stability due to the restraint of harmful Y-NiMo phase formation during the thermal exposure at the high temperature above 1 000 °C. And the reason may be that the addition of Ru increased the degree of Mo supersaturation in both γ and γ' phases, and hence suppressed the precipitation of Y-NiMo phase. The results of stress rupture tests under the testing condition of 1 100 °C, 120 MPa showed that the addition of 2% Ru in the alloy improved the stress rupture lives significantly for thermal exposed samples. The improvement of the stress rupture properties may be attributed to the restraint of Y-NiMo phase precipitation and growth by the addition of the proper amount Ru.