Lattice-parameter misfits between the γ and γ′ phases in single crystals of nickel superalloys

X-ray diffractometry has been used to study the transformation of the profiles of X-ray diffraction lines (222), (004), (003) and to determine the values of the lattice misfit between the γ and γ′ phases (γ/γ′ misfit) for single crystals of nickel superalloys ZhS6U, ZhS30, ZhS32, VZhM1, and VZhM4 in the as-cast state and after heat treatment. It has been established that with an increase in the γ/γ′ misfit there increase tetragonal distortions of the fcc lattice of the γ solid solution. For the single crystals of VZhM4 alloyed with rhenium and ruthenium, splitting of the superlattice reflection of the strengthening γ′ phase has been revealed. The structural regularities revealed testify to qualitative changes in the factors that govern the redistribution of refractory alloying elements between the lattices of the γ and γ′ phases, for example, of Mo in the presence of Re and Ru.