Microstructure and Internal Stresses in Cyclically Deformed Al and Cu Single Crystals

Abstract

The concept of “long range internal stresses” (LRIS) is often utilized to explain various aspects of the mechanical behavior of materials, including cyclic deformation and the Bauschinger effect. These internal stresses are usually associated with the heterogeneous dislocation microstructure (Straub et al. [1] and Tippelt et al. [2]). More specifically, it has long been suggested that long-range internal stresses (LRIS) develop with plastic deformation in metals and alloys in association with the development of a subgrain boundaries, cell walls, dipole bundles, etc. The evidence to support the existence of LRIS has included Bauschinger experiments, dislocation radii measurements, stress-dip tests and, especially, and more recently, asymmetry in x-ray diffraction line profiles (XRD LPA) in association with the “composite model.” Convergent beam electron diffraction, weak-beam dislocation dipole separation measurements and in-situ transmission electron microscopy were all performed by the author on cyclically deformed Al and Cu single crystals (Kassner et al. [3, 4, 5]). These provide insight into the mechanisms of cyclic plasticity but especially indicate an absence of measurable LRIS.