| Summary: | This study investigated the effects of a minor Zr addition (0.15 wt%) and heterogenization treatment (one-stage/two-stage) on the hot-working temperature and mechanical properties in Al-4.9Cu-1.2Mg-0.9Mn alloy. The results indicated that the eutectic phases (α-Al + θ-Al<sub>2</sub>Cu + S-Al<sub>2</sub>CuMg) dissolved after heterogenization, retaining θ-Al<sub>2</sub>Cu and τ<sub>1</sub>-Al<sub>29</sub>Cu<sub>4</sub>Mn<sub>6</sub> phases, while the onset melting temperature increased to approximately 17 °C. A change in the onset melting temperature and evolution of the microstructure is used to assess an improvement in hot-working behavior. With the minor Zr addition, the alloy exhibited enhanced mechanical properties due to grain growth inhibition. Zr-added alloys show 490 ± 3 MPa ultimate tensile strength and 77.5 ± 0.7 HRB hardness after T4 tempering, compared to 460 ± 2.2 MPa and 73.7 ± 0.4 HRB for un-added alloys. Additionally, combining minor Zr addition and two-stage heterogenization resulted in finer Al<sub>3</sub>Zr dispersoids. Two-stage heterogenized alloys had an average Al<sub>3</sub>Zr size of 15 ± 5 nm, while one-stage heterogenized alloys had an average size of 25 ± 8 nm. A partial decrease in the mechanical properties of the Zr-free alloy was observed after two-stage heterogenization. The one-stage heterogenized alloy had 75.4 ± 0.4 HRB hardness after being T4-tempered, whereas the two-stage heterogenized alloy had 73.7 ± 0.4 HRB hardness after being T4-tempered.
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