Effects of microalloying with Ag, Li, and Sc on hot-deformed microstructure of Al–Mg–Si–Cu alloys

Abstract

The effects of microalloying with Ag, Li, and Sc on the hot-extruded microstructures of Al–Mg–Si–Cu alloys were studied. Each microalloying element was observed to affect the hot-deformed microstructure of the alloy, with a retarding effect on its recrystallization; however, the effect of Ag-addition was relatively small. The number fraction of grains with a high Taylor factor and their kernel average misorientation significantly increased when Li and Sc were added to the Al–Mg–Si–Cu alloy, implying a strong anisotropy of slip. It was also found that Li-addition primarily weakened the C component, whereas Sc-addition significantly strengthened the rotated copper (Rt-Cu) component in the deformation texture, and strongly dissipated the recrystallization texture. Additionally, all the microalloying elements slightly increased the dislocation density and fraction of edge dislocations. Thus, a very close dislocation arrangement with a strong screening of dislocations was observed; however, this effect was relatively weak for the Sc-added alloy. The high variation in the microstructural parameters of the Sc-added alloy was understood to depend primarily on the Al3Sc dispersoid and its effect on the other precipitates. In contrast, Ag- and Li- additions did not significantly change the relatively large precipitate structure, which implies that there were changes in the nanoscale precipitates or solute clustering during the hot deformation of Ag- and Li-added alloys.