Enhanced dispersion hardening and mechanical properties of Al-Mg-Si-Cu-Mn alloy by regulation of icosahedral quasicrystalline dispersoids

Abstract

This study reported a novel low-temperature homogenization treatment designed to enhance dispersion hardening, recrystallization resistance, and mechanical properties of an Al-Mg-Si-Cu-Mn alloy. The optimized homogenization process (400 °C for 2 h) can significantly promote the formation of a large number of fine icosahedral quasicrystalline I-Al(Mn, Fe)Si dispersoids, resulting in a 9417.6 % increase in dispersoid number density and an 85.8 % reduction in dispersoid size compared to conventional high-temperature homogenization. Additionally, this treatment alters the dispersoid/Al interface from semi-coherent to coherent. Although the primary phases do not dissolve during this low-temperature homogenization, they can be effectively fragmented and dissolved during subsequent thermomechanical processing. After rolling, solution treatment and aging treatment, the low-temperature homogenized sample retains a refined dispersoid distribution compared to other samples, achieving maximum mechanical strength with a yield strength of 402.1 MPa, an ultimate tensile strength of 451.1 MPa, and an elongation of 12 %. This enhancement is primarily attributed to the high density of nano-sized dispersoids, which provides substantial dispersion strengthening to the alloy. However, the I-dispersoids are less effective in controlling recrystallization behavior during solution treatment. Overall, these findings offer new insights into improving the strength and elongation of Al-Mg-Si-Cu alloys.