Deformation parameters governing tensile elongation for a mechanically milled Al-1.1at.%Mg-1.2at.%Cu alloy tested in tension at constant true strain rates

For a mechanically milled Al-1.1at.%Mg-1.2at.%Cu alloy. tensile deformation was carried out at temperatures of 523-823 K and at true strain rates of 1 x 10(-3)-5 x 10(0)/s. The analysis of true stress-true strain curves from a dislocation dynamics viewpoint showed that a large value of re-mobilization probability of unlocked immobile dislocations Omega is mainly responsible for an enormous elongation (1.3 in true strain) observed at an intermediate strain rate (100/s) and temperature (748 K). Discussion on thermally activated process for Omega and dislocation kinetics indicated that the suppression of plastic instability leading to superplastic elongation is controlled by liberating immobile dislocations from a solute atmosphere. The strain rate sensitivity m was formulated on a basis of dislocation dynamics, and a relation of Omega proportional to m(2) was found to field between them. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. AN rights reserved.