Formation of Deformation Twins and Related Shear Bands in a Copper Single Crystal Deformed by Equal-Channel Angular Pressing for One Pass at Room Temperature

Abstract

Deformation twinning, which is extremely difficult to produce in face-centered cubic (FCC) crystals with medium to high stacking fault energy (SFE), was observed in pure copper single crystals with an appropriate crystallographic orientation subjected to equal-channel angular pressing (ECAP) for one pass at room temperature. Dense shear bands were also observed, delineated by large-angle grain boundaries, and with close to a twinning relation with the matrix, suggesting the role of deformation twinning at their nucleation sites. The activation of deformation twinning is rationalized by a favorable crystallographic orientation and predominant dislocation density in a primary slip system.

Effect of Simple Shear Deformation Prior to Cold Rolling on Texture and Ridging of 16% Cr Ferritic Stainless Steel Sheets

“…25,26) Additionally, ECAP can be designed for a continuous process, 27,28) and combined with other processing such as cold-rolling. In our previous studies, we found that dense deformation twins and micro-shear bands with local orientation splitting formed in copper during ECAP by one pass, 29) Since activation of slip is limited to slip systems nearly parallel to the macroscopic shear plane, strain hard- The effect of simple shear deformation by equal-channel angular pressing (ECAP) for one pass on the texture and ridging of ferritic stainless steel sheets with 16 mass% chromium has been investigated. Hot rolled and annealed sheets of 4 mm thickness were ECA-pressed for one pass, prior to cold rolling and final annealing.…”

Twinning in polycrystalline aluminium deformed by dynamic channel angular pressing

“…3b. Along with such thick twin-oriented bands, individual twin lamellae were observed in the matrix by TEM in [28]. It is the author's opinion that thick bands were formed by a coalescence of such microtwins, inheriting their orientation [28].…”

“…In contrast with twinning in copper, observed during quasi-static deformation by ECAP [28], in aluminum, which is characterized by higher stacking fault energy and higher dislocation mobility, deformation twining can occur only under high strain-rate dynamic deformation (DCAP). …”

“…By contrast, the twins described in the present study as well as the "macrodeformation twins" observed by Zhao et al in Al single crystals [22] were up to tens of micrometers in thickness. To understand this controversy, a study of Miyamoto et al [28] may be of interest. They observed mesoscopic (5 to 10 μm in thickness) twin-oriented shear bands in copper single crystals deformed by ECAP.…”

Misorientation Change of the Grain Boundary in Pure Copper Bicrystals Subjected to One-Pass Equal-Channel Angular Pressing

“…14) Most of these reports seem to support, explicitly or implicitly, the grain subdivision as the grain refining mechanism, where the subboundaries emerge inside the grains and increase their misorientation with increasing strain. 5) In the overall SPD processing, equal-channel angular pressing (ECAP) is unique in that the deformation proceeds by incremental shear restricted to the narrow zone parallel to the intersecting plane of the two channels.…”