Reorientation and stress relaxation due to twinning:: Modeling and experimental characterization for Mg

A study of the mechanical response of Mg AZ31 when deformed under twinning dominated conditions is presented. In addition to the well-known rapid texture variation, neutron diffraction measurements reveal a 'sense-reversal' of the internal stress in the twinned grains. The latter is characterized experimentally and an elasto-plastic polycrystal model is extended in order to account for twin domain reorientation and associated stress relaxation. It is concluded that the texture variation due to twinning is sufficient to explain the observed macroscopic stress-strain response. However, the evolution of internal stresses in diffracting subsets of grains is complex and more challenging to explain. It seems to be strongly controlled by the order in which slip and twinning are activated, the stress relaxation associated with twin propagation, and neighbor constraint effects. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.