When 10:00 AM - 11:00 AM Jun 02, 2020
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PhD Defense: “Effects of Dopant Additions on the High Temperature Oxidation Behavior of Nickel-based Alumina-forming Alloys”


Talia Barth
Marquis Group

Nickel-based alloys continue to play a crucial role for high temperature applications due to their excellent mechanical properties. Despite their high strength, toughness, and creep resistance, these alloys are vulnerable to aggressive oxidation and corrosion upon exposure to air at high temperature, limiting their application space. To promote oxidation resistance, nickel is typically alloyed with aluminum, which enables the formation of a stable, slow-growing layer of Al2O3 on the alloy surface that limits the loss of the metal. Minor alloying element additions are well-known to reduce Al2O3 scale growth rate and can make a substantial difference in extending the lifetime of a high temperature component, yet many of the mechanisms for these beneficial dopant effects are unclear.

The current work aims to elucidate the mechanisms by which common dopants, known to improve oxidation resistance of commercial alloys, modify α-Al2O3 growth. Model NiAl and NiCrAl alloys doped with Ti, Y, and Si were oxidized at temperatures from 950-1200 °C, and high-resolution characterization techniques were used to probe the resulting alumina scale microstructure and chemistry. In particular, the effects of minor alloying additions on alumina scale development in the early stages of oxidation and Al/O transport through an established alumina scale after longer exposures were investigated.

Through its systematic approach, this work examined specific aspects of the complex oxidation process and clarified the mechanisms by which different dopant elements affect scale growth. The new knowledge gained can be used for the development of highly oxidation resistant alloys and predictive models of oxidation rate that are critical for industrial applications.

To join Talia's defense, go to: 

umich.zoom.us/j/99014772114

Password: 677420