Effect of solution heat treatment on the microstructure of hot-rolled Al-Mg-Si 6xxx alloy microalloyed with Sc and Zr

• A deformable Al-Mg-Si 6xxx alloy containing Sc and Zr is being developed. • The alloy is intended to combine between high strength and thermal stability. • Solutionizing affects the optimum coexistence of Mg-Si and Al 3 (Sc,Zr) precipitates. • Solutionizing at 500 °C lessened β″ precipitates relative to that at 530 °C. • Al 3 (Sc,Zr) dispersoids were better maintained after solutionizing at 500 °C. Developing high-strength, thermally stable Al-Mg-Si 6xxx alloys with Sc and Zr is challenging due to mismatched heat treatment requirements between Al-Mg-Si and Al-Sc-Zr systems. This study investigated how solution treatment temperature affects the balance between Mg-Si precipitates and Al 3 (Sc,Zr) dispersoids—key contributors to strength and thermal stability—in an Al-0.67Mg-0.67Si-0.5Cu-0.08Sc-0.08Zr alloy. Two solution treatments were conducted at 500 and 530 °C for 15 min. Solutionizing at 500 °C reduced β″ precipitation compared to that at 530 °C but maintained fine Al 3 (Sc,Zr) dispersoids, which coarsened and dissolved at 530 °C. Thus, the 500 °C treatment can offer a more favorable balance of strength and thermal stability for dual-property optimization in Sc- and Zr-modified 6xxx alloys.