ANOMALOUS TENSILE STABILITY FOR AN ALUMINUM ALLOY AT HIGH TEMPERATURES AND HIGH STRAIN RATES INTERPRETED FROM A DISLOCATION DYNAMIC VIEW POINT

摘要

Tensile tests were conducted by keeping the true strain rate constant throughout deformation,over wide ranges of strain rates (10~(-3) - 5 x 10~0/s) and temperatures (523 -823 K). True stress-true strain curves were computer-simulated using a constitutive equation based on dislocation dynamics to generate important deformation parameters. A pronounced tensile stability takes place rather at an intermediate temperature (748 K) and a high strain rate (1 x 10~0/s). Both strain-dependent stain rate sensitivity, m and strain hardening parameter, γ could be calculated by using the deformation parameters obtained from simulation as a function of strain, so that tensile stability can graphically be estimated, which coincides well with that visually observed from experiments.