Effect of high pressure torsion on the precipitation hardening in Al–Ca–La based eutectic alloy

The effect of high pressure torsion (HPT) on the structure and microhardness of Al3Ca2La1·5Mn alloy containing 13 vol% of Al4(Ca,La) eutectic phase has been studied using electron microscopy, X-ray analysis and atom probe tomography (APT). We show that HPT causes the formation of a nanocrystalline structure resulting in a 4-fold increase in the microhardness (to 2.5 GPa) of the alloy. Post-deformation low-temperature annealing further increases the microhardness to ~3.1 GPa. The APT data suggest that the increase in the microhardness after annealing is caused by precipitation hardening due to the decomposition of the calcium and manganese supersaturated aluminum solid solution. •The microhardness of the Al3Ca2Ca1·5Mn alloy after high-pressure torsion increases to 2.5 GPa.•Atom probe tomography showed that the Ca solubility in Al solid solution increases 10-fold to 0.06 at.% after HPT.•Annealing at 150–175°С showed an additional increase in the microhardness by 25% (up to ~3.1 GPa).•Ca and Mn concentration in the Al solid solution after aging decreases by ~2 and ~6 times, respectively.•The annealing-induced hardening can be caused by the precipitates hardening with formation of 5–10 nm precipitates.