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 degrees C for 8 h, fine and homogeneous beta" 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 similar to 18.9% in tensile strength and similar to 23.9% in ductility are obtained after seven R-Conform passes and followed by aged at 175 degrees C for 8 h.

本工作研究了经反复连续挤压成形工艺（R - Conform工艺）以及后续人工时效处理的连铸连轧Al - Mg - Si合金的微观结构和力学性能。结果表明，R - Conform工艺可有效提高Al - Mg - Si合金的抗拉强度和延展性，且随着Conform道次的增加，抗拉强度和延展性同时提高。力学性能的提高与R - Conform工艺过程中过饱和固溶体的逐步形成以及具有高位错密度的细化且均匀分布的亚结构有关。对于在175℃下人工时效8小时的R - Conform后的Al - Mg - Si合金，由于R - Conform工艺过程中动态应变再溶解（DSR）的强大驱动力，形成了细小且均匀的β″沉淀强化相。因此，与时效后的连铸连轧Al - Mg - Si合金相比，经过7次R - Conform道次并随后在175℃下时效8小时后，抗拉强度提高了约18.9%，延展性提高了约23.9%。