Optimizing a Nickel-Based Superalloy Composition

The Brief

Jet engine turbine blades are made from nickel-based superalloys like Inconel, which need to balance high-temperature strength against oxidation resistance. Working with a hypothetical Ni-16Cr-3.4Al alloy under a fixed solution (1050°C) and aging (800°C) heat-treatment cycle, the brief was to use CALPHAD-based computational thermodynamics to model the alloy's microstructure and optimize its aluminium and chromium content against competing performance objectives.

My Role

This was an individual project: I ran all the Thermo-Calc modeling, derived the property models linking simulated phase data to strength and oxidation resistance, wrote the MATLAB optimization scripts, and authored the full technical report.

Engineering Highlights

• CALPHAD modeling: Used Thermo-Calc (NIDEMO thermodynamic database) to compute phase equilibria, mapping how the strengthening γ′ (Ni₃Al) precipitate phase fraction varies with both aging temperature and alloy composition.
• Aging temperature analysis: Quantified the strength-temperature relationship, showing that lowering the aging temperature from 800°C to 450°C increased the precipitate strengthening contribution from 231 MPa to 590 MPa — and explained why 800°C is still the practical choice.
• Multi-objective optimization: Built a normalized performance index in MATLAB combining strength and oxidation resistance from Thermo-Calc-derived equilibrium data, identifying the Al concentration that best balances the two competing properties.
• Two-variable optimization: Extended the model to jointly vary Al and Cr, using grid heat maps and phase diagrams to find a composition that maximizes strength while respecting phase-stability and precipitate-fraction constraints.
• Trade-off analysis: Evaluated the interplay between strength, oxidation resistance, and alloy density (via the rule of mixtures) for aerospace weight considerations.

Results