Negative to positive strain rate sensitivity in 5xxx series aluminum alloys: Experiment and constitutive modeling

Uniaxial tension and compression tests, at both quasi-static and dynamic ranges of loadings, are utilized to study the thermo-mechanical response of an AA5182-O sheet. The strain rate at quasi-static regime ranges from 10−4 to 100 (s−1) and at dynamic loading is chosen to be around 3500 (s−1). Measurements are reported at temperatures of 296 K, 338 K, 373 K, 423 K, and 473 K. While at temperatures lower than the critical temperature of Tc, the flow stress decreases with increase of strain rate during quasi-static loading; above this temperature, the measured response shows positive strain rate sensitivity at the same strain rate range. In contrast, significant positive strain rate sensitivity prevails at dynamic loading over the whole range of temperature. A constitutive model is proposed to predict the stress–strain response of the alloy over the studied strain rate and temperature ranges. The developed model is also calibrated for another AA5xxx alloy series, AA5754-O, to evaluate the capability of the developed model in capturing transition from negative to positive strain rate sensitivity.