Cost-Effective Thermomechanical Processing of Nanostructured Ferritic Alloys: Microstructure and Mechanical Properties Investigation

• Published in: Materials Vol. 17; no. 19; p. 4763
• Main Authors: Lin, Yan-Ru, Zhao, Yajie, Su, Yi-Feng, Byun, Thak Sang
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 28.09.2024; MDPI
• Subjects: Alloys; atom probe tomography (APT); Chemical composition; Cost analysis; Crystal structure; Deformation effects; Dental caries; Dispersion hardening alloys; Dispersion strengthening; Ductility tests; Economic aspects; Electron back scatter; Fusion reactors; Grain size; Grain structure; High temperature; Investigations; Irradiation; Mechanical milling; Mechanical properties; Mechanical tests; Microstructure; Nanoparticles; Nanostructure; nanostructured ferritic alloys; Nitrides; nuclear materials; oxide dispersion strengthened (ODS) alloys; Plastic deformation; Radiation; Reactors; Scanning electron microscopy; Scanning transmission electron microscopy; Software; Specialty metals industry; Swelling; Thermomechanical analysis; Thermomechanical properties; Thermomechanical treatment; Transmission electron microscopy; transmission electron microscopy (TEM); nuclear materials; transmission electron microscopy (TEM); atom probe tomography (APT); oxide dispersion strengthened (ODS) alloys; mechanical properties; nanostructured ferritic alloys
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma17194763

Nanostructured ferritic alloys (NFAs), such as oxide-dispersion strengthened (ODS) alloys, play a vital role in advanced fission and fusion reactors, offering superior properties when incorporating nanoparticles under irradiation. Despite their importance, the high cost of mass-producing NFAs through mechanical milling presents a challenge. This study delves into the microstructure-mechanical property correlations of three NFAs produced using a novel, cost-effective approach combining severe plastic deformation (SPD) with the continuous thermomechanical processing (CTMP) method. Analysis using scanning electron microscopy (SEM)-electron backscatter diffraction (EBSD) revealed nano-grain structures and phases, while scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectroscopy (EDS) quantified the size and density of Ti-N, Y-O, and Cr-O fine particles. Atom probe tomography (APT) further confirmed the absence of finer Y-O particles and characterized the chemical composition of the particles, suggesting possible nitride dispersion strengthening. Correlation of microstructure and mechanical testing results revealed that CTMP alloys, despite having lower nanoparticle densities, exhibit strength and ductility comparable to mechanically milled ODS alloys, likely due to their fine grain structure. However, higher nanoparticle densities may be necessary to prevent cavity swelling under high-temperature irradiation and helium gas production. Further enhancements in uniform nanoparticle distribution and increased sink strength are recommended to mitigate cavity swelling, advancing their suitability for nuclear applications.