The role of thermal expansion and composition changes in the temperature dependence of the lattice misfit in two-phase γ/γ′ superalloys

The relative role of thermal expansion and composition changes in the temperature dependence of the lattice misfit in γ/γ′ alloys was investigated on the basis of ab initio calculations. We show that over a wide temperature range, up to approximately 0.6Tmelt, the lattice misfit is determined by the difference in thermal expansion of γ and γ′ phases and exhibits only a slight variation. For higher temperatures, the redistribution of the major alloy components between the phases becomes a leading contribution to the lattice misfit.