Effect of applied stress on γ’-rafting behavior in a Ni-based single-crystal superalloy: experiments and finite element analysis
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The effect of applied tensile stress on the γ′-rafting behavior for a Ni-based single-crystal superalloy with more negative misfit was investigated. By conducting interrupted creep tests at high temperature, it indicated that the increase in the applied stress accelerates the γ′-rafting (directional coarsening of γ′ phase). In the early stage of rafting, the γ′-cubes start interconnecting at the ends of the parallel-to-applied-stress γ′-channel. The distributions of misfit stress, coherent strain and strain energy density of the γ/γ′ phases are then calculated by finite element analysis. The calculation results show that the rafting acceleration is mainly ascribed to the reduced strain energy density in the parallel-to-applied-stress γ-channel that is driven from the couple interaction of external load and misfit stress. Interface dislocation network formation, resulting from the misfit-induced increase in resolved shear stress, also contributes to the γ′-rafting.
KeywordsNi-based superalloy High lattice misfit Rafting Finite element analysis Misfit stress Strain energy density
This work was financially supported by the National Natural Science Foundation of China (Nos. U1435207, 51771007, 51671015) and National Defense Basic Scientific Research Project (No. A2120132006).