The origins of room temperature hardening of Al-Cu-Mg alloys

The most commonly cited mechanisms for the rapid age hardening of Al-Cu-Mg alloys at about 100-200degreesC are hardening by Guinier-Preston B zone formation, formation of Cu-Mg co-clusters and a dislocation-solute interaction mechanism. New experiments on ageing-deformation-ageing cycles at room temperature indicate that no substantial additional age hardening occurs with the addition of deformation to the cycle, and hence, a dislocation-solute interaction mechanism appears unlikely. Instead, strengthening due to modulus hardening generated by the difference in shear modulus of Cu-Mg co-clusters and matrix is proposed as the main strengthening mechanism for room temperature hardening. (C) 2004 Elsevier B.V. All rights reserved.