Solid-Solution Strengthening Effects in Binary Ni-Based Alloys Evaluated by High-Throughput Calculations

Abstract

Solid solution strengthening and precipitate strengthening play vital roles in imparting the extraordinary performance of the Ni-based singe-crystal superalloys. Further enhancement of their performance relies heavily on a systematic and quantitative understanding of the effect of potential solutes in Ni. In this work, high throughput density functional theory calculations were carried out to examine the binary solid solutions formed between 35 potential alloying elements from the 2nd to the 6th period of the periodic table and Ni with different solute concentrations. The calculated composition dependent lattice constants and elastic constants were employed to analyze the strengthening effects of the alloying elements based on the Labusch model. It is found that their strengthening ability depends on their positions on the periodic table, and shows regular variation against the atomic number. Elements in both ends of each period tend to have higher strengthening ability than those in the middle, and the lattice misfit is found to dominate the strengthening effect for elements in the 5th and 6th period. Stability analysis reveals that all the solid solution models are dynamically stable and intrinsically ductile. Thermodynamic consideration based on solution enthalpy finds that roughly half of the elements are prone to form solid solutions with Ni, their solubility however cannot be derived readily. By using the experimental solubility, the strengthening potential were evaluated and promising strengthening elements are identified. In particular, Re is found to have weak strengthening ability and strengthening potential, its crucial role in Ni-based superalloys comes primarily from its retardation of diffusion under high temperature applications.