Abstract
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
Δ
H
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
Δ
H
of quasi-ternary Ni31X alloys of Ni (the γ phase) and the
Δ
H
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.
Funder
Defence Research and Development Organisation