Al-Sm alloys under far-from-equilibrium conditions

Abstract

Traditional Al alloys have shown tremendous potential in the aerospace industry due to their attractive properties such as ductility, fracture toughness, and fatigue resistance. However, modern aerospace applications call for next-generation Al alloys with a stringent combination of properties such as high strength, low density, and excellent environmental stability. In that sense, we studied highly driven Al-Rare-Earth (RE) alloys under far-from-equilibrium conditions to investigate the possible effects of cooling rate on the expected microstructure, thus mechanical properties. Al94Sm6 was produced using a copper wheel melt spinner. XRD analysis showed the Sm is entirely trapped within the Al matrix. The heat-treated specimens resulted in the formation of the nanocrystalline Al4Sm phase embedded in the Al matrix, with a two-step precipitation sequence. The hardness values determined by nanoindentation shows that the initial supersaturated solid solution has 3.83 GPa hardness, while the heat-treated ones have 3.34 GPa. The mechanisms behind this extreme strength and ductility through solute trapping, and subsequent heat-treatments were discussed in detail using a combined study of micromechanical characterization, nanoindentation , electron microscopy, XRD, and DSC.