Two-dimensional grain boundary sliding and mantle dislocation accommodation in ODS ferritic steel

Abstract

The mechanism governing grain boundary sliding (GBS) accommodated by dislocation and microstructural evolution in regions II/III and III was studied to understand superplasticity.Two-dimensional GBS that occurred during high-temperature shear in oxide dispersion strengthened ferritic steel exhibiting an elongated and aligned grain structure was analyzed using surface markers drawn by focused ion beams. In addition, the accommodating dislocation structure was evaluated by electron back-scattered diffraction and electron channeling contrast imaging. In the initial stage of deformation, GBS triggered dislocation slippage in "mantle" areas near grain boundaries. These mantles tended to appear around GBS-resistant areas such as curved boundaries and grain protrusions. Next, the mantle dislocations generated dislocation walls before forming low-angle boundaries (LABs) along {110} crystallographic planes via dynamic recovery at the core/mantle boundaries. Finally, secondary GBS or rigid rotation occurred at the newly formed LABs to compensate for the initial GBS and resulted in continuous dynamic recrystallization. These mantle dislocation activities and substructural evolution mechanisms were graphically modeled and validated by comparison with previous studies. Keywordssuperplasticity, continuous dynamic recrystallization, dynamic recovery, electron back-scattered diffraction (EBSD), electron channeling contrast imaging (ECCI)

Stress-induced amorphization triggers deformation in the lithospheric mantle

“…This regime is characterized by striking microstructures showing abundant evidence for displacements across grain boundaries, either parallel (sliding) or perpendicular (opening, cavitation) to the boundaries (see black arrows in Figures 1c, d and e). Such microstructures have already been reported in metallic alloys (alpha iron-tin alloys 21 , Ni-Cr alloys 22 , steel 23 ) and germanates 24 , and interpreted as evidence of GBS. At 1050 °C, boundaries often show evidence of local ductility, with serration and presence of an intergranular amorphous material (see black arrows in Figure 1).…”

Analysing the Interaction between Microscopic Deformation, Microstructure and Void Evolution of Near-α Titanium Alloys during Non-Superplastic Hot Deformation by an Integrated Crystal Plasticity Finite Element Model

“…Alabort et al calculated the equilibrium cell size ( λ ) of Ti-6Al-4V with the similar equiaxed microstructure to that of Figure 2 a, in which the calculated results are in the same order of magnitude as that of Figure 14 a [ 31 ]. The accumulated dislocations are mainly composed of the most easily activated slip systems, namely the prismatic slipping in this paper, as shown in Figure 8 c. Masuda et al also proposed a similar mechanism, discovering that a transgranular slipping along activated to accommodate the GBS, as the primary slip system in BCC-structured steel [ 39 ].…”

“…Several subgrain boundaries that extended into grain A also formed, thereby dividing grain A into multiple subgrains. The intragranular deformation bands served as the main mechanism for grain fragmentation, i.e., continuous dynamic recrystallisation (CDRX) [ 39 , 43 ]. At the same time, the deformation band near the GBs brought about the dislocation accumulation, which resulted in the GB bowing out to form the nucleation of discontinuous dynamic recrystallisation (DDRX) [ 44 ].…”

Effect of Rolling Deformation on Creep Properties of FeCrAl Alloys

“…region II but was around 20 in regions I and III (Masuda et al, 2016;Kamikawa et al, 2018). The creep deformation mechanism of the cooperative grain boundary sliding was found for FeCrAl ODS alloy (Kamikawa et al, 2018), and the creep constitutive model related to the interparticle distance was proposed for FeCrAl ODS alloy (Ukai et al, 2020).…”