Behaviour of Al-Mg-Si alloys at a wide range of temperatures and strain rates

• Three Al-Mg-Si alloys are investigated at different temperatures and strain rates.
• Local strain measurement is performed with an image based technique.
• The three aluminium alloys exhibit a high temperature and strain rate sensitivity.
• Their strain rate sensitivity is shown to evolve with temperature and deformations.
• A physically based model is fitted to the data and provides reasonable agreement.

The thermo-mechanical behaviour in tension of three as-cast and homogenized Al-Mg-Si alloys, distinguished by their Mg and Si content, was investigated at a wide range of strains (the entire deformation process up to fracture), strain rates (0.01–750 s–1) and temperatures (20–350 °C). The alloys were shown to have isotropic plastic behaviour. Low and medium strain-rate tests were performed in a universal testing machine, while a split-Hopkinson tension bar (SHTB) system was used for higher strain rates. The samples were heated with an induction-based heating system. In all tests, local recordings of the specimen geometry with digital cameras allowed determining the true stress-strain curve also after the onset of necking. In addition, the failure strains of all samples were measured after the tests. The three alloys had high ductility, even at room temperature, which increased with increasing temperature. It was shown that both the yield strength and the work-hardening decreased with increasing temperature. The materials exhibited negligible strain-rate sensitivity (SRS) for temperatures lower than 200 °C, while they revealed strong positive SRS at higher temperatures. The experimental data obtained for the Al-Mg-Si alloys were used to identify the parameters of a physically-based constitutive model proposed in the literature, and reasonable agreement with the experimental stress-strain behaviour was achieved.