Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

The elastic properties of the Al-Mg-Si direct-chill-cast AA6111 alloy were determined during the unloading stage of the cyclic tensile test over a wide range of temperatures (25-550 °C), and particular attention was paid to high temperatures near the solidus. Young’s modulus was calculated based on macroscopic and localized strains, which were measured using an extensometer and the digital image correlation (DIC) method. Poisson's ratio was determined based on the localized axial and lateral strains measured using DIC method. Over the entire temperature range, the DIC method demonstrated a higher stability in its accuracy with increasing temperature than that using the extensometer. A sharp change in the slope of Young's modulus as a function of the temperature, starting from the solidus temperature, was detected using the DIC method. Correlations between Young's modulus and temperature in both the solid and semi-solid states were established. Poisson’s ratio as a function of the temperature exhibited a dramatic change near the solidus temperature because of the presence of liquid pockets. The onset brittle temperature of AA6111 alloy in the semi-solid state was estimated to be 550 °C based on the critical values of Poisson’s ratio and the shear modulus to bulk modulus ratio.