Effect of High-Density Nanoparticles on Recrystallization and Texture Evolution in Ferritic Alloys

• Main Authors: Eda Aydogan, Connor J. Rietema, Ursula Carvajal-Nunez, Sven C. Vogel, Meimei Li, Stuart A. Maloy
• Format: Article
• Language: English
• Published: MDPI AG 2019-03-01
• Series: Crystals
• Subjects: nano-structured ferritic alloys (NFAs); FeCrAl alloys; nano-oxides (NOs); neutron diffraction; texture; recrystallization
• Online Access: https://www.mdpi.com/2073-4352/9/3/172

Ferritic alloys are important for nuclear reactor applications due to their microstructural stability, corrosion resistance, and favorable mechanical properties. Nanostructured ferritic alloys having a high density of Y-Ti-O rich nano-oxides (NOs < 5 nm) are found to be extremely stable at high temperatures up to ~1100 °C. This study serves to understand the effect of a high density of nano-particles on texture evolution and recrystallization mechanisms in ferritic alloys of 14YWT (14Cr-3W-0.4Ti-0.21Y-Fe wt %) having a high density of nano-particles and dispersion-free FeCrAl (13Cr-5.2Al-0.05Y-2Mo-0.2Si-1Nb wt %). In order to investigate the recrystallization mechanisms in these alloys, neutron diffraction, electron backscattered diffraction, and in situ and ex situ transmission electron microscopy have been utilized. It has been observed that even though the deformation textures of both the 14YWT and FeCrAl alloys evolved similarly, resulting in either the formation (in FeCrAl alloy) or increase (in 14YWT) in γ-fiber texture, the texture evolution during recrystallization is different. While FeCrAl alloy keeps its γ-fiber texture after recrystallization, 14YWT samples develop a ε-fiber as a result of annealing at 1100 °C, which can be attributed to the existence of NOs. In situ transmission electron microscopy annealing experiments on 14YWT show the combination and growth of the lamellar grains rather than nucleation; however, the recrystallization and growth kinetics are slower due to NOs compared to FeCrAl.