Oxide nanoparticles in an Al-alloyed oxide dispersion strengthened steel: crystallographic structure and interface with ferrite matrix

Abstract

. Oxide nanoparticles in an Al-alloyed oxide dispersion strengthened steel: crystallographic structure and interface with ferrite matrix. Philosophical Magazine, 97(21), 1824-1846 . DOI: 10.1080/14786435.2017 Oxide nanoparticles in an Al-alloyed oxide dispersion strengthened steel: crystallographic structure and interface with ferrite matrix Oxide nanoparticles are quintessential for ensuring the extraordinary properties of oxide dispersion strengthened (ODS) steels. In this study, the crystallographic structure of oxide nanoparticles, and their interface with the ferritic steel matrix in an Al-alloyed ODS steel, i.e. PM2000, were systematically investigated by high resolution transmission electron microscopy. The majority of oxide nanoparticles were identified to be orthorhombic YAlO3. During hot consolidation and extrusion, they develop a coherent interface and a near cuboidon-cube orientation relationship with the ferrite matrix in the material. After annealing at 1200 C for 1 hour, however, the orientation relationship between the oxide nanoparticles and the matrix becomes arbitrary, and their interface mostly incoherent. Annealing at 1300 C leads to considerable coarsening of oxide nanoparticles, and a new orientation relationship of pseudo-cube-on-cube between oxide nanoparticles and ferrite matrix develops. The reason for the developing interfaces and orientation relationships between oxide nanoparticles and ferrite matrix under different conditions is discussed.

Microstructure Characterization and Mechanical Properties of Al Alloyed 9Cr ODS Steels with Different Al Contents

“…In this work, it is obvious that the oxide particle size is highly related to the content of Al, the particles are increased along with the increase of Al content (from 0.4% to 2.5%) and again decreased when further increase the Al content (from 2.5% to 4.5%). But overall, the particles size of Al alloyed ODS steels is larger than that of Ti alloyed ODS steels, which is agreement with the reported results . Further work will be focused on the micro‐alloy element design, such as the addition of Zr, Hf to decrease the oxide particles size in the Al added low Cr ODS steels.…”

Response of oxide nanoparticles in an oxide dispersion strengthened steel to dynamic plastic deformation

“…not pure yttria anymore, but alloyed with other elements from the steel matrix. Due to the significance of the oxide nanoparticles, oxide nanoparticles have been extensively studied with respect to their composition, crystallographic structure and interface with iron matrix [4][5][6][7][8][9][10][11][12]. In general, for ODS steels containing aluminium, the oxide nanoparticles are found to be yttrium-aluminium oxide [4][5][6][7][8]; whereas in ODS steels without aluminium but with titanium, the oxide nanoparticles are identified as yttrium-titanium oxide [9][10][11][12].…”

“…Due to the significance of the oxide nanoparticles, oxide nanoparticles have been extensively studied with respect to their composition, crystallographic structure and interface with iron matrix [4][5][6][7][8][9][10][11][12]. In general, for ODS steels containing aluminium, the oxide nanoparticles are found to be yttrium-aluminium oxide [4][5][6][7][8]; whereas in ODS steels without aluminium but with titanium, the oxide nanoparticles are identified as yttrium-titanium oxide [9][10][11][12]. Although there are large discrepancies in the reported crystallographic structure of the oxide nanoparticles and their orientation relationship with the matrix even for the same material, the common conception about oxide nanoparticles is that they are both, strong and stable.…”

“…Compared to the number of studies on identifying the oxide nanoparticles [4,6,8,9], the interface between oxide nanoparticles and matrix [8,[10][11][12], the thermal stability and the irradiation performance of various ODS steels [13][14][15][16], there are only few results available regarding the behaviour of the oxide nanoparticles when the ODS steels are subjected to plastic deformation. The latter is of high importance, since processing of ODS steels inevitably involves plastic deformation, and any changes in the structure and morphology of the oxide nanoparticles caused by plastic deformation may alter the mechanical properties (and the irradiation tolerance) of ODS steels.…”

Influence of Al Addition Strategy on the Microstructure of a Low‐Cr Oxide Dispersion‐Strengthened Ferritic Steel

“…However, in the previous literature, the addition of aluminum tends to reduce the mechanical properties of ODS steels. [18,19] It is because that compared with the Al-free ODS steels, the grains and dispersed oxides of the Al-containing ODS steels are much larger in size due to the coarsening effect of Al addition on the steel matrix and Y 2 O 3 particles, [16,[20][21][22] which generally results in obvious reduction of strength. Moreover, most of the previous studies were based on the microstructure observation of the ODS steels in the final state (e.g., as forged or as extruded).…”