Characterization of dislocation structures in copper single crystals using electron channelling contrast technique in SEM

Abstract

The dislocation structures induced by low-plastic-strain-amplitude cyclic deformation of [111] multiple-sliporiented Cu single crystals were investigated using electron channelling contrast (ECC) technique in scanning electron microscopy (SEM). At a low plastic strain amplitude γ pl of 8.8 × 10 -5, the saturated dislocation structure is mainly composed of labyrinth-like vein structure (or irregular labyrinths), and the cyclic hardening behavior at such a low γ pl is interpreted as being the result of dislocation multiplication by a FrankRead mechanism. As γ pl increases to 4.0 × 10 -4 , the unsaturated dislocation structure exhibits two kinds of distinctive configurations, i.e., dislocation walls and misoriented cells. Interestingly, these misoriented dislocation cells are strictly aligned along the primary slip plane (111), constituting a unique persistent slip band (PSB) structure. Here, these cells are thus called PSB cells. In addition, there is a locally distinctive region comprising some cells having a recrystallization-like feature in the whole structure of PSB cells. The formation of the structure of PSB cells is discussed.

Latent hardening effects in low cycle fatigue of copper single crystals

“…The micrograph reveals the old dislocation cell substructure in not fully condensed form, formed during primary fatigue of the parent sample #c, visible in the upper part of the micrograph. The substructure is very similar to the cell structure formed in [111] single crystals fatigued at a strain amplitude of 0.92 Â 10 À3 reported by other authors [23,26]. The size of the primary cells is in the range 0.6-0.8 microns and the cells are somewhat elongated, indicating some unbalanced activity among operating slip systems.…”

“…DBI and DBII develop due to a gradual increase of lattice rotations and therefore they often appear together, in conjugate orientations related to each other, and are Philosophical Magazine 273 observed in a broad range of orientations including single and double slip crystals [14,24,25]. Veins, cells and dislocation wall structures are the most common patterns in the h111i region of orientations and they appear in the order of increasing strain amplitude [25,26]. Finally, the so-called labyrinth structure composed of two sets of mutually perpendicular dislocation walls (rungs) on {001} planes, with one wall family always formed perpendicular to the stress axis, is a characteristic dislocation arrangement for single crystals with the orientation of the tensile axis in the neighborhood of h100i [11,25,27,28].…”

Deformation mechanisms of CoCrFeMnNi high-entropy alloy under low-cycle-fatigue loading

“…For microstructural based modeling, the type of dislocation structure formation based on grain orientation is of particular interest. It is well-known that for FCC single crystals (e.g., copper, nickel), PSB-wall and labyrinth structures dominate in near [011] and [001]-oriented grains (// LD), respectively [49], while in near [111]-oriented grains, vein and cell structures are found at low and high strain amplitudes, respectively [49,50].…”

Precise analysis of effects of aging on mechanical properties of cast ADC12 aluminum alloy

“…From the TEM images of the GC and HMC samples ( Fig. 8(a)), there is clearly intersection of dislocation walls with dislocation cells, with a complicated pattern for GC sample A [16]. In contrast, submicrometer-sized grains and fine dislocation cells are observed for HMC sample A.…”