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 Al3Ti particles through powder thixoforming. The results indicate that the volume fraction of soft domains (primary alpha-Al grains) decreases while that of hard domains (secondarily solidified structures) gradually increases with increasing partial remelting temperature of powder thixoforming. The corresponding het-erogeneity 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 celcius exhibits a prominent combination of ultimate tensile strength, yield strength, elastic modulus, uniform elongation, and elon-gation 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 ef-fectively weakened due to multiple microcracks and the microcrack deflection dissipates more energy, which further leads to the increase of ductility.(c) 2022 Elsevier B.V. All rights reserved.