Fabrication of a novel multiscale structured 5083 Al alloy with improved tensile properties via mechanical milling and spark plasma sintering

In the present study, bulk multiscale structured 5083 Al alloy with controlled microstructure was successfully fabricated by mechanical milling and spark plasma sintering. Microstructure observation revealed that due to the self-assemble of near-spherical powders (prepared by low-energy ball milling) and flaky powders (prepared by high-energy ball milling), near-harmonic structures were realized, i.e., the coarse grains (CGs) with retained dislocations were surrounded by fully recrystallized ultrafine grains (UFGs). Moreover, the volume fraction of the CGs and the UFGs can be easily manipulated by changing the composition of powders. Room temperature tensile tests suggested that the multiscale structured bulk samples exhibited significantly enhanced mechanical properties. For example, an ultimate tensile strength up to 460 MPa was realized in the sample consolidated from 20% near-spherical powders and 80% flaky powders. The strengthening and deformation mechanisms of the bulk samples and the strategies for further optimizing the mechanical properties of multiscale structured materials were discussed.