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Yajie Zhao

Yajie Zhao.What is your thesis topic?
My thesis project focuses on the stability of Cr-enriched alpha prime (α’) precipitates in high purity FeCr alloys under heavy ion irradiation conditions.

How is materials processing involved in your research?
Ion irradiation is an important and complicated material processing method, which could both destroy the nanoscale precipitates by forming damage cascades and enhance the precipitate formation by accelerating the diffusion process. We performed ion irradiations on high purity FeCr alloys at different temperatures and ion fluxes. Using focused ion beam (FIB) for sample preparation and atom probe tomography (APT) as the main characterization method, the evolution of α’ precipitation as a function of irradiation conditions is studied.

Provide an example of where the material, process, or properties you are studying might find an application.
Ferritic-martensitic (FM) steels with high Cr concentration are promising structural materials for Generation IV fission and fusion reactors mainly due to their superior void swelling resistance compared to conventional austenitic steels. However, high-Cr FM steels are known to undergo pronounced hardening and embrittlement due to the formation of dislocation loops and Cr-rich α’ precipitates. My study will help to understand the kinetics of α’ precipitation and thus provide knowledge about how to mitigate this mechanical degradation problem.