Influence of scandium addition on microstructure and mechanical properties in nickel-based superalloys: An integrated multiscale modeling and experimental approach

Abstract

Microalloying has long been recognized as an effective method for improving the mechanical properties of metallic materials and developing new ones. In this study, we comprehensively investigate the effects of Sc addition on the microstructural evolution and mechanical performance of nickel-based superalloys using a combination approach of the experiment, first-principles calculation, and multiscale modeling. The results show that Sc addition simultaneously improves the yield strength increasing from 1068 MPa to 1172 MPa (9.7%) and elongation increasing from 13.4% to 19.7% (47%). The microstructural characterizations reveal that Sc addition refines the grain size, increases the volume fraction of primary precipitate, induces the coarsening of secondary precipitates, and produces a new type of Sc-rich particle. First-principles calculations from the atom probe tomography experiment show that the anti-phase boundary energy of secondary precipitate is significantly increased in Sc-containing superalloys. A modified alloying-dependent yield strength model is developed by considering the multimodal precipitate size distribution and microstructure evolution obtained from experiments and atomic simulations. The increased yield strength originates from not only the Sc addition induced increased volume fraction of primary precipitate at grain boundary to enhance grain boundary strengthening, but also Sc addition induced increased anti-phase boundary energy of secondary precipitate to improve the precipitate strengthening. The increased elongation depends on the fact that the Sc element has a good affinity to deleterious elements and forms Sc-rich particle and oxygen-rich precipitate to enhance grain boundary strength. This work integrating multiscale modeling and experiment can be denoted as a universal framework to study the influence of alloy element on the microstructure and properties, which gives guiding significance to screen and design high-performance superalloys.