Enhancement of strength–ductility synergy in heterostructured 2024Al alloy through tailoring heterogeneity level

To conquer the trade-off between strength and ductility, a new strategy for preparing heterostructured (HS) 2024Al alloys with various heterogeneity levels through introducing submicro-Al3Ti particles and adjusting partial remelting duration of powder thixoforming was proposed. The results indicate that the difference in volume fraction between soft and hard domains of the resultant HS alloys gradually decreases from 0.27 to 0.02, while that of microhardness also decreases from 1.58 to 1.17 GPa, i.e., the heterogeneity level gradually decreases with prolonging the remelting time. The excellent strength–ductility synergy is simultaneously achieved by a moderate heterogeneity level (the differences in microhardness of 1.23 GPa and volume fraction of 0.02) in the HS alloy thixoformed at the partial remelting time of 80 min. This is primarily ascribed to the largest strain gradient caused by the accumulation of the highest density dislocations at the boundary during deformation, which produces the highest heterodeformation-induced (HDI) strengthening and hardening. In addition, the dislocations emitted from the submicro-Al3Tip during the later deformation stage also improve the strain strengthening and hardening, further leading to the improvement in strength–ductility synergy.