The influence of Al:Nb ratio on the microstructure and mechanical response of quaternary Ni-Cr-Al-Nb alloys

The influence of Al:Nb ratio on the microstructure and properties of Ni-Cr-Al-Nb alloys has been investigated following long-term exposure at elevated temperatures. The γ′ volume fraction, size and lattice misfit were seen to increase with a larger Al:Nb ratio, although these changes resulted in reduced hardness. The change in the critical resolved shear stress (CRSS) associated with strong dislocation coupling was determined to be the dominant strengthening mechanism and increased with decreasing Al:Nb ratio. A distribution of tertiary γ′ was observed to be necessary in maximising the mechanical properties of these alloys.