On crystallographic texture in real face-centred cubic single crystals

The paper discusses the instability of the strain ratio and crystallographic orientation in face-centred cubic (fcc) real single crystals exposed to uniaxial straining. This behaviour can be described by the r(ε) function defining the variation of plastic anisotropy with strain, even in nominally stable crystals with [100], [111] or [110] orientation. The instability is due to the error in the orientation of the sample axis (a is the angle between the sample and the [uvw] nominal direction) and/or to microscatter of the crystallographic orientation in the whole volume of a single crystal (described by the half-width of the rocking curve p). The instability and, consequently, texture in single crystals have been shown to depend on the stacking fault energy (y). A quantitative evaluation of the instability of the crystallographic orientation in deformed single crystals has been proposed and its physical meaning revealed in experiments on low (Cu-Zn alloys, Ag)-, medium (Cu)- and high (Ni, Al)-stacking fault energy metals. Two different mechanisms should be assumed when investigating the influence of stacking fault energy on the instability of the crystallographic orientation in deformed fcc single crystals: changing from one mechanism to another, when y varies from γAg to γCu.