Influence of rolling and precipitate processes on microstructure and high-temperature mechanical properties of Al-Mg-Si-Mn alloys

This study systematically investigates the influence of the sequence between rolling and precipitation processes on the microstructural evolution and high-temperature mechanical properties of heat-treatable Al-Mg-Si-Mn alloy, aiming to provide a theoretical basis for optimizing the manufacturing process and enhancing the overall performance of such alloys. Al-Mg-Si-Mn alloy slabs with excellent surface quality were successfully produced using an independently developed twin-roll casting (TRC) technique. Microstructural analysis shows that under the precipitation-rolling (P-R) process with prolonged precipitation treatment, the average size of precipitates is approximately 70 nm, with a number density of 15 μm^-2. In contrast, the rolling-precipitation (R-P) process combined with short-duration precipitation treatment increases the average precipitate size to 90 nm and raises the number density to 17 μm^-2. Under identical precipitation durations, the R-P process leads to a pronounced spheroidization trend of the dispersion phases, accompanied by the formation of extensive recrystallized microstructures. High-temperature mechanical tests indicate that at 350 ℃, the R-P processed alloy achieves a tensile strength of 83 MPa with an elongation of 5%, while the P-R processed alloy exhibits a tensile strength of 65 MPa and an elongation of 6%. The study demonstrates that the R-P process promotes the precipitation of a greater number of strengthening phases within a shorter time, thereby significantly improving the mechanical properties of the alloy under high-temperature conditions. This provides new insights for optimizing short-process routes for heat-treatable strengthened alloys.