|Research:||Evolution of Precipitates in Ni-Based Superalloys|
|Education:||B.Eng Metallurgical Engineering, McGill University|
|Publications:||Publications by Booth-Morrison in our database|
Materials Science and Engineering
2220 North Campus Drive
Evanston, IL 60208
I am a fourth-year graduate student studying the temporal evolution of model nickel-based superalloys by atom-probe tomography (APT).
The recent surge in fuel costs, and the threat of global warming, have amplified the urgency for increased fuel efficiency in high-performance engines. Engine fuel efficiency is directly related to engine operating temperature, which is tied to the high-temperature properties of the engine materials. Due to their excellent strength and resistance to both corrosion and creep-induced damage at operating temperatures up to 1373 K, nickel-based superalloys are used for critical components of both aerospace and land-based turbine engines. The high-temperature performance of these materials is due primarily to strengthening of the primary γ-matrix phase by the precipitation of a secondary γ'-phase. The decomposition of the γ-matrix via the formation of nanoscale γ'-precipitates is the main subject of my thesis research.
I study the kinetic pathways of the γ-/γ'- phase transformation using high-resolution experimental techniques, namely APT and electron microscopy. Figure 1 below shows the cuboidal g'-precipitates that form in the γ-matrix of a model Ni-Al-Cr-Ta alloy at 1073 K. In-depth analysis of datasets such as the one shown Figure 1, provide details about the temporal evolution of the γ'-precipitate properties and compositions. These results, in concert with simulations employing advanced computational methods such as first-principles calculations, and Monte-Carlo and thermodynamic simulations, elucidate the kinetic pathways that lead to phase decomposition at high-temperatures. The development of future generations of nickel-based superalloys that can withstand higher operating temperatures will rely on a detailed understanding of the γ/γ'- phase transformation. These complex multi-component alloys will serve as the building blocks for advanced turbine engines that will require less fuel, and produce fewer CO2 greenhouse gas emissions.
We are interested in studying the kinetic pathways which lead to the decomposition of the γ-matrix phase of model nickel-based superalloys via the formation of nanometer-sized γ'-precipitates. APT analysis provides an in-depth look at the compositional and nanostructural evolution of the γ’-precipitate phase as it evolves. The details of the decomposition of the γ-matrix phase, from the early stages of solute-rich γ'-nuclei formation, to the subsequent growth and coarsening of the γ’-precipitates, can then be accessed within the framework of classical nucleation, growth and coarsening theories. Computational modeling employing Grand Canonical and Lattice Kinetic Monte Carlo, and the software programs ThermoCalc, Dictra and PrecipiCalc, further elucide the kinetic pathways that lead to phase decomposition.
The addition of Ta to a Ni-Al-Cr base alloy results in the formation of a large volume fraction of Ta-enriched γ'-precipitates. Ta has been shown to be a strong γ'-precipitate former and solid-solution strengthener and is known to improve high-temperature strength, and resistance to creep, fatigue and corrosion. By combining APT, electron microcopy and computational modeling, we have been able to study the effects of a dilute addition of Ta on the base Ni-Al-Cr system.