Microstructure Characteristics, Texture Evolution and Mechanical Properties of Al–Mg–Si–Mn–xCu Alloys via Extrusion and Heat Treatment

Abstract

In this work, the impact of extrusion and post-extrusion heat treatment (T6) on the microstructure and mechanical properties of the Al-1.2Mg-0.8Si-0.5Mn alloy with different Cu contents (0, 0.6, 1.3 and 2.0 wt%) was studied. Microstructure characterization showed that all extruded alloys exhibited elongated grain structure with an average grain size of ~ 4.8 μm. The dominant texture components were deformation texture (A*, Copper and P texture), while the proportion of random texture initially increased and then decreased with increasing Cu content. After T6 treatment, the grain size of the four alloys increased significantly, but the growth trend decreased with increasing Cu content, and the textures transformed into recrystallized textures (Cube, A and Goss texture). Tensile testing revealed that the designed T6 alloys with 2.0% Cu content exhibited an excellent strength-ductility balance, i.e., a yield strength of 342.9 MPa, an ultimate tensile strength of 424.8 MPa and an elongation of 15.9%. The enhanced strength was mainly attributed to fine grain strengthening, solid solution strengthening and aging strengthening mechanisms. The superior ductility was due to the pinning effect of fine precipitates and high dislocation accommodation capacity caused by heat treatment.