Local order in industrial and model γ phases of superalloys Original Research Article

Different γ phase model alloys of nickel base superalloys are investigated as a function of temperature using elastic diffuse neutron scattering, macroscopic tensile tests, TEM post mortem observations and in situ straining experiments. Short Range Order (SRO) of (1 1/2 0) type resulting from nano-domains with correlation lengths of 0.5–1 nm is observed in all alloys. The dislocation distribution confirms the presence of short-range ordered nano-domains with a size of about 0.7 nm. In all the alloys, the influence of SRO on the deformation mechanisms is clear at low and medium temperature and thus explains the similarities of the deformation behaviour observed in this temperature range. From 750°C to 1000°C, the deformation microstructure becomes progressively homogeneous which suggests the decrease of SRO as illustrated by a decrease of diffuse scattering intensities at the (1 1/2 0) positions on heating. The various techniques applied prove to be complementary in the investigation of complex solid solutions.