Optimizing the mechanical properties of Al-1.2Mg-0.8Si-0.5Mn-1.3Cu alloy by controlling the solution treatment temperature

In this work, the effect of solution temperature on the microstructure and mechanical behavior of an extruded Al-1.2Mg-0.8Si-0.5Mn-1.3Cu alloy after T6 treatment was investigated. Microstructural analysis revealed a temperature-dependent transformation mechanism. With rising solution temperature from 500 °C to 580 °C, static recrystallization occurred, with grain coarsening from 22.25 μm to 97.13 μm, and the formation of equiaxed grains. Higher temperature promoted the dissolution of coarse precipitates and enhanced recrystallization textures (R-Cube, A, and B textures), while random texture initially increased and then decreased. A critical threshold was identified at 580 °C, where over-burning began to compromise structural integrity. Mechanical testing revealed that hardness and tensile properties (ultimate tensile strength: 381.6 MPa, yield strength: 312.2 MPa, and elongation: 17.2%) improved up to 540 °C but deteriorated at 580 °C. Although finer precipitates formed during the subsequent aging enhanced the precipitation strengthening, excessive solution temperature (>540 °C) prioritized defect formation, negatively affecting the overall mechanical performance. This work offers essential insights into the thermal processing-property relationships of high-performance Al alloys.