Effects of Scandium and Zirconium Addition on Recrystallization Behavior of Al–Mg–Si Alloy

Abstract

The effects of thermally stabilized particles on the recrystallization behavior of an Al–Mg–Si alloy were investigated to obtain the fundamental knowledge for controlling the microstructure, texture, and mechanical properties of this alloy. In this study, the Al–Mg–Si–Sc–Zr alloy was cast, homogenized, and hot-rolled. Three types of spherical Al3(Sc, Zr) particles with L12 structure, rod-like incoherent, spherical semi-coherent, and spherical incoherent particles, were observed in a hot-rolled sample of the Al–Mg–Si–Sc–Zr alloy using transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and energy-dispersive X-ray spectroscopy (EDS). In addition, three-dimensional electron tomography (3D-ET) and STEM-EDS revealed that all particles have a core-shell structure with a Sc-enriched core and a Zr-enriched shell. It is considered that these particles are formed during casting, homogenized treatment, and hot rolling. The crystal orientation distribution of the sample after cold rolling indicated that the presence of Al3(Sc, Zr) particles may interfere with the recrystallization (grain growth) until 600°C. Comparison with the driving force of primary recrystallization and grain growth, and the pinning force of Al3(Sc, Zr) particles, showed that these particles mainly contribute to the suppression of grain growth. The results of an in-situ heating SEM/EBSD analysis of the cold-rolled Al–Mg–Si–Sc–Zr alloy supported this suggestion.