Abstract
Research on multicomponent superalloys derived from Ni3Al shows that certain elemental additions congregate at the boundary of the γ/γ′ interface while certain others partition into either the γ or the γ′ phases. Such microstructural features have a strong bearing on the performance of the superalloy. However, no established correlations exist as of now, that can help predict such a behavior. The present work addresses this issue by examining the properties of the quasi-ternary alloys of Ni3Al and brings out correlations to selected lumped parameters related to the elemental properties. Computation of thermodynamic properties of 11 alloys of quasi-ternary Ni24Al7X system was carried out from first principles using Wien 2k and Gibbs2 code on a supercell constructed with 32 atoms. Elements X substituted at the Al site are selected from the information derived from the literature. Systematic variations are shown to occur in compressibility and heat of formation ΔH of the alloys with average electron concentration, elemental radii and/or electronegativity of the constituent elements in the alloys. Analysis of the data computed for a supercell on ΔH of quasi-ternary Ni31X alloys of Ni (the γ phase) and the ΔH of Ni24Al7X alloys (the γ′ phase) explains the possible reason for the enrichment of elements like Re and W at the γ/ γ′ interface. Trends in the observed correlations correctly predict the experimental observations on alloying effects reported from spectroscopic studies on quasi-ternary alloys of Ni3Al. The scope of predicting alloying behavior based on basic elemental properties gains significance in the design of superalloys.
Published Version
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