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 r ate of 10(0) s(-1) exhibited a maximum (approximate to 1.25 in true strain epsilon) at an intermediate temperature of 748 K, neither at the lowest, 57 3 K (epsilon approximate to 0.17) nor at the highest, 823 K (epsilon approx imate to 0.44). Further, grain deformation was found to contribute to a gre ater extent to the total elongation at 748 K than grain boundary sliding. I n 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 co mbination of the largest re-mobilization probability of unlocked immobile d islocations, the highest mobile dislocation density and the modest immobili zation rate of dislocations is responsible for the largest uniform elongati on at 748 K. (C) 1999 Elsevier Science S.A. All rights reserved.