Dynamic strain ageing in an AlMg alloy at different strain rates and temperatures: Experiments and constitutive modelling

Abstract

Uniaxial tension tests at strain rates from 10−4 to 10−1s−1 and temperatures from 298 to 418 K are performed to study the dynamic strain ageing (DSA) of an AA5182-O sheet. Digital image correlation (DIC) is used to obtain the stress-strain curves and characterize the heterogenous deformations. A constitutive model based on the mechanical threshold stress (MTS) framework is then proposed and used to calculate the stress–strain response at different strain rates and temperatures. The modified MTS model captures the dependence of the strain rate sensitivity (SRS) on strain, temperature and strain rate both inside and outside the Portevin–Le Chatelier (PLC) domain. Special attention is paid to re-interpret the occurrence of stress serrations. It is found that the competition between work hardening and DSA leads to different jerky flow scenarios. The modified MTS model is used to predict the PLC domain as a function of strain rate and temperature. To further test the validity of the model at various temperatures and alloys, it is also approximately calibrated to Ni-based superalloys, for which it captures earlier reported behaviour at elevated temperatures.