Influence of scandium on an Al-2% Si alloy processed by high-pressure torsion

Research highlights: → Al3Sc precipitates in Al-2% Si alloy lead to higher strength and smaller grains. → After 5 turns in high-pressure torsion, grain size is ∼0.15 μm and strength ∼375 MPa. → Ball indentation is effective for measuring the mechanical properties. - Abstract: High-pressure torsion (HPT) was used to process Al-2% Si and Al-2% Si-0.25% Sc alloys for up to five turns and the mechanical properties of the processed materials were evaluated using the ball indentation technique (BIT). The results show that the presence of Al3Sc precipitates is effective in producing higher strength levels and greater grain refinement in the Al-2% Si-0.25% Sc alloy. The introduction of scandium reduces the grain size of the Al-2% Si alloy from ∼0.38 to ∼0.15 μm after 5 turns of HPT and the corresponding maximum tensile strength is increased from ∼325 to ∼375 MPa. The grain and substructure formation in the Al-2% Si alloy is similar to aluminum with dislocation cell formation and a reasonably recovered microstructure whereas in the Al-2% Si-0.25% Sc alloy it is non-homogeneous with arrays of non-equilibrium boundaries and dislocation tangles within the grains.