Bi-modally structured pure aluminum for enhanced strength and ductility

Highlights: • A bi-modally structured pure Al with high strength and enhanced ductility is obtained using conventional powder metallurgy techniques. • The powder mixing technique plays an important role in the final structure produced. • Mixing by ball milling leads to microstructural refinement and homogeneity of bimodal structure. - Abstract: Nanostructured metals are known to suffer from reduced ductility which limits their industrial applications. In this work, the ductility of nanostructured aluminum is enhanced by developing a bi-modal microstructure comprised of mechanically milled hard aluminum particles dispersed in a soft aluminum matrix. Both low energy (96 RPM) and high energy (200 RPM) solid-state mixing techniques are employed to blend the hard and soft powders. Both optical microscopy and electron backscatter diffraction (EBSD) revealed that a finer bi-modal structure is achievable upon using high energy ball milling and results in improved performance. The capacity for strain hardening is also enhanced and attributed to the observed dislocations in the coarse-grained regions of the material, as confirmed by transmission electron microscopy (TEM) analysis. The results of this work demonstrate that high strength bi-modally structured pure Al with enhanced ductility can be obtained using conventional P/M techniques.