Analysis of the temperature dependence of tensile elongation for a mechanically milled Al–1.1 at.%Mg–1.2 at.%Cu alloy by a dislocation dynamics approach

For a mechanically milled and thermo-mechanically treated Al–1.1 at.%Mg–1.2 at.%Cu alloy, the uniform elongation in tension test at a nominal strain rate of 100 s−1 exhibited a maximum (≈1.25 in true strain ε) at an intermediate temperature of 748 K, neither at the lowest, 573 K (ε≈0.17) nor at the highest, 823 K (ε≈0.44). Further, grain deformation was found to contribute to a greater extent to the total elongation at 748 K than grain boundary sliding. In order to explain such a dependence of elongation on temperature, the true stress–true strain behaviors were analyzed from a viewpoint of dislocation dynamics by computer simulation. The simulation results indicate that a combination of the largest re-mobilization probability of unlocked immobile dislocations, the highest mobile dislocation density and the modest immobilization rate of dislocations is responsible for the largest uniform elongation at 748 K.