Enhanced mechanical properties of an Al-Mg-Si alloy by repetitive continuous extrusion forming process and subsequent aging treatment

The microstructure and mechanical properties of a continuous casting and rolling Al-Mg-Si alloy subjected to repetitive continuous extrusion forming process (R-Conform process) and subsequent artificial aging treatment are investigated in this work. The results show that R-Conform process can effectively improve both tensile strength and ductility of the Al-Mg-Si alloy, in which tensile strength and ductility are simultaneously improved with increasing Conform passes. The enhanced mechanical properties are associated with the progressively formation of supersaturated solid solution and refined and homogenous distributed substructures with high dislocation densities during R-Conform process. For the post-R-Conform artificial aged Al-Mg-Si alloy at 175 °C for 8 h, fine and homogeneous β'' precipitation strengthening phases are formed due to the great driving force of dynamic strain redissolution (DSR) during R-Conform process. Thus, compared to the aged continuous casting and rolling Al-Mg-Si alloy, an increase of ~18.9% in tensile strength and ~23.9% in ductility are obtained after seven R-Conform passes and followed by aged at 175 °C for 8 h.