Effects of Hf and/or Ti addition on the morphology, crystal, and metal/oxide interface structures of nanoparticles in FeCrAl-ODS steels
Tian-Xing Yang, Peng Dou, Zhan-Xing Li, Xinyu Xiao
Abstract
FeCrAl oxide dispersion strengthened (ODS) steel is one of the most promising candidate cladding materials due to its exceptional properties. For 3.8Al–0.46Hf (Fe–15Cr–2W–3.8Al–0.46Hf–0.32Y 2 O 3 ) and 3Al–0.1Ti–0.6Hf (Fe–15Cr–2W–3Al–0.1Ti–0.6Hf–0.35Y 2 O 3 ) ODS steels, the morphologies of matrix grains & nanoparticles , and the crystal structures of oxides & metal/oxide interface structures were studied by scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). For 3.8Al–0.46Hf and 3Al–0.1Ti–0.6Hf ODS steels, the mean grain size is 1.26 μm and 0.90 μm, respectively, and the dispersion morphology of nanoparticles in the latter is better than that of the former. Crystal & interface structures of 313 and 222 oxides in 3.8Al–0.46Hf and 3Al–0.13Ti–0.6Hf ODS steels were characterized, respectively. The proportions of Y–Hf–O and Y–Al–O particles in the former are 63.3 % and 29.1 %, respectively. However, the Y–Hf–O, Y–Al–O, and Y–Ti–O particles in the latter account for 74.8 %, 16.7 %, and 8.5 %, respectively. The much better dispersion morphology of oxides in 3Al–0.1Ti–0.6Hf ODS steel, relative to 3.8Al–0.46Hf ODS steel, is due to the much higher proportion of Y–Hf–O, the considerably lower proportion of Y–Al–O and the fairly high number fraction of Y–Ti–O. The study delved into the formation mechanisms of various oxides and the strengthening mechanisms in both ODS alloys.