Dislocation Structures in a Cyclically Deformed Single-Slip-Oriented Fe-35 wt pct Cr Alloy Single Crystal Containing Fine Cr-Rich Precipitates

Abstract

The dislocation structures induced by the cyclic deformation of a \( [\bar{1}49] \) single-slip-oriented Fe-35 wt pct Cr alloy single crystals containing fine Cr-rich precipitates have been studied by transmission electron microscopy (TEM) over the plastic strain amplitude epl range of 5 × 10−4 to 5 × 10−3. Persistent slip bands (PSBs) with different structures, such as ladder-like structure, irregular ladders, elongated cells, etc., were observed to form at plastic strain amplitudes ranging from 5.0 × 10−4 to 2.5 × 10−3, and the volume fraction of PSBs increases with increasing epl. As epl is as high as 5.0 × 10−3, dislocation cells dominate the microstructure, even though a small amount of irregular PSB ladder structures still exists and they tend to evolve as labyrinth-like structures. The instability of Cr-rich precipitates during cyclic straining was believed to facilitate the formation of PSBs and thus promote some similarities of cyclic deformation characteristics between the current body-centered cubic (bcc) Fe-Cr single crystals and face-centered cubic (fcc) metal crystals. Whatever the internal structure of PSBs is, they could always carry the majority of the plastic strain in the course of cyclic deformation, thus causing the occurrence of a stress plateau region in the cyclic stress–strain (CSS) curve of Fe-Cr alloy single crystals.