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 Original Research Article

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 1×10−3–5×100/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 Ω 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 Ω 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 Ω∝m2 was found to hold between them.