A comparison of the mechanical behaviour of an AA1050 and a low carbon steel deformed upon strain reversal

Strain reversal tests are performed at large strains on an AA1050 aluminium alloy and a low carbon steel deformed in simple shear. The forward and reverse loading are performed either at room temperature or at -120degreesC. A transient stagnation in the hardening rate is recorded at reloading for both materials in any temperature sequence. Only the extent of the plateau is material and temperature sensitive. A dislocation cell structure is always observed in the prestrained aluminium alloy. In contrast, the dislocation distribution is homogeneous in the steel when prestrained at low temperature. As the dislocation substructure evolution upon strain reversal is different for these cases, it is concluded that structural features like cell disintegrations are not responsible but merely correlated to the measured transient stagnation of the hardening rate. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.