Synthesis of heterogeneity-improved heterostructured 2024Al alloy with excellent synergy of strength and ductility via powder thixoforming

Designing a heterostructure with reasonable increase in heterogeneity is a promising way for improving strength-ductility synergy of metals. In this work, heterogeneity-improved heterostructured 2024Al alloys with differences in volume fractions of soft and hard domains have been fabricated via forming in situ fine Al ₃ Ti particles through powder thixoforming. The results indicate that the volume fraction of soft domains (primary α-Al grains) decreases while that of hard domains (secondarily solidified structures) gradually increases with increasing partial remelting temperature of powder thixoforming. The corresponding heterogeneity level of heterostructured 2024Al alloys improves with the increase of the volume fraction of hard domains. The resulting alloy fabricated at the remelting temperature of 655 ℃ exhibits a prominent combination of ultimate tensile strength, yield strength, elastic modulus, uniform elongation, and elongation to failure of 455 MPa, 291 MPa, 73.34 GPa, 7.95%, and 8.65% at room temperature, presenting an enhancement of 41.7%, 39.9%, 9.4%, 3.9%, and 4.1% compared with those of the corresponding 2024Al matrix alloy, respectively, i.e., the trade-off between strength and ductility has been well overcome. These good mechanical properties are attributed to the reasonably improved heterogeneity level, i.e., the reasonably increased microhardness difference between the two domains and volume fraction of hard domains. The high strength is mainly attributed to the improved hetero-deformation induced (HDI) strengthening. The excellent ductility is primarily ascribed to the HDI hardening. In addition, the high localized stress is effectively weakened due to multiple microcracks and the microcrack deflection dissipates more energy, which further leads to the increase of ductility.