Constitutive Model Over Wide Temperature Range and Considering Negative-to-Positive Strain Rate Sensitivity for As-Quenched AA2219 Sheet

An accurate constitutive model over a wide temperature range is very important for research on the quenching process. In this study, uniaxial tension tests of an as-quenched AA2219 aluminum alloy sheet were first conducted at different strain rates (10⁻³-10⁻¹ s⁻¹) over a wide temperature range (298-773 K). The tension results showed an increase in the strain rate sensitivity (SRS) from negative to positive with temperature. Different increasing trends were observed in the low-temperature range (298-473 K), high-temperature range (573-773 K), and transitive-temperature range (473-573 K). In order to more accurately capture these variations in the SRS, the existing function that considers the negative-to-positive SRS was modified by adding a coupling effect term for the temperature and strain rate. The temperature sensitivity increased linearly and exponentially with the strain and temperature, respectively, and also had obviously different tendencies in the low- and high-temperature ranges. The new coupling effect term for the temperature and strain was constructed to consider these effects. Finally, a phenomenological constitutive model was proposed, in which the negative-to-positive SRS and the coupling effects of the strain and temperature were considered. This constitutive model could predict the flow stress of the as-quenched AA2219 with very good correlation over a wide temperature range.