Local order in industrial and model gamma phases of superalloys

Different gamma phase model alloys of nickel base superalloys are investiga ted as a function of temperature using elastic diffuse neutron scattering, macroscopic tensile tests, TEM post mortem observations and in situ straini ng experiments. Short Range Order (SRO) of (1 1/2 0) type resulting from na no-domains with correlation lengths of 0.5-1 nm is observed in all alloys. The dislocation distribution confirms the presence of short-range ordered n ano-domains with a size of about 0.7 nm. In all the alloys, the influence o f 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 degreesC to 1000 degreesC, the deformatio n microstructure becomes progressively homogeneous which suggests the decre ase of SRO as illustrated by a decrease of diffuse scattering intensities a t the (1 1/2 0) positions on heating. The various techniques applied prove to be complementary in the investigation of complex solid solutions. (C) 20 01 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reser ved.