Quantitative study on the correlation between microstructure and mechanical properties of additive friction stir deposited 6061-T6 Al-Mg-Si alloy

Abstract

Additive friction stir deposition (AFSD) technology is attractive for its ability to create freeform and fully dense structures without melting and solidification. Hence, AFSD is an alternative to fusion-based additive manufacturing technology. However, the quantitative relationship between mechanical properties and microstructure has not been established yet. The purpose of the research is to establish a quantitative relationship between the microstructure and mechanical properties of AFSD-ed 6061-T6 aluminum alloy. In this study, 6061-T6 aluminum alloy feedstock was processed using AFSD technology and then subjected to post-deposited heat treatment (PDHT). The microstructure evolution and mechanical properties of the feedstock, as-deposited and PDHT-ed 6061-T6 aluminum alloy specimens, were investigated for a comparative study. The microstructure was analyzed using electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Hardness testing and tensile testing were conducted for the feedstock, as-deposited, and PDHT-ed specimens. The strengthening mechanisms were discussed. It was found that precipitation strengthening was the main strengthening mechanism for feedstock and PDHT-ed specimens, which contributed to 69% and 83% of the total yield strength, respectively. Whereas grain refinement strengthening was the main strengthening mechanism for the as-deposited specimen, which occupied 68% of the total yield strength. Finally, the relationship between microstructure and mechanical properties of additive friction stir-deposited 6061-T6 Al–Mg–Si alloy was quantified.