Abstract:The effect of non-isothermal aging treatment on microstructure and mechanical properties of in-situ AA2024-Al₃NiCu composite fabricated by the stir casting process was examined. The Al₃NiCu intermetallic was created by adding 3 wt.% nickel powder during stir casting and homogenization treatment at 500 °C for 24 h after casting. The microstructural results obtained using optical and scanning electron microscope indicate that, after non-isothermal aging treatment, the S-Al₂CuMg precipitates become finer, forming a poor zone of this precipitate in the area between the dendrites. Also, adding nickel during stir casting reduces the precipitation rate and the contribution of S-Al₂CuMg precipitates in strengthening composite during non-isothermal aging. The maximum hardness, ultimate tensile strength, and toughness achieved in the 3 wt.% nickel-containing sample after non-isothermal aging at 250 °C are (121.30±4.21) HV, (221.67±8.31) MPa, and (1.67±0.08) MJ/m³, respectively. The maximum hardness and ultimate tensile strength of AA2024-Al₃NiCu composite are decreased by 6% and 4%, respectively, compared to those of nickel-free AA2024 aluminum alloy.

Key words: AA2024 aluminum matrix composite; stir casting method; non-isothermal aging treatment; Al₃NiCu reinforcement