"Effects of Neutron Irradiation on the Microstructure and Mechanical Properties of Ferritic-Martensitic Steels" 

Saquib Bin Habib, MSE PhD Candidate 

Advisor: Professor Janelle Wharry

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ABSTRACT

Ferritic and martensitic (F-M) steels with high chromium content are developed for high temperature applications, offering resistance to void swelling and superior thermal properties compared to austenitic stainless steels. The modified 9Cr-1Mo F-M steel, known as grade 91/T91, was developed in the 1980s with improved strength and creep characteristics. These steels are considered for use in high-dose components of Generation IV nuclear plants due to their resistance to void swelling. Irradiation damage in materials is caused by high-energy particles, such as neutrons, which displace atoms from their normal lattice positions, creating vacancies and interstitials. This displacement cascade can lead to the formation of defect clusters, which can significantly affect the material's microstructure and, consequently, its macroscopic mechanical properties. Despite the extensive studies on the effects of neutron irradiation on the mechanical properties and microstructures of F-M steels, there is still a gap in understanding the microstructure-property relations and fracture behavior of these alloys after irradiation, especially when manufactured using advanced techniques like powder metallurgy with hot-isostatic pressing (PM-HIP). Advanced manufacturing techniques can produce components with fewer defects. Further research is needed to explore the performance of these advanced F-M steels under neutron irradiation for next-generation nuclear reactors.