High strength Mg/Nb nanolayer composites

We report on the microstructure and mechanical properties of sputter-deposited Mg/Nb multilayer films, with individual layer thickness, h, of 2.5–200 nm. High resolution TEM studies reveal the formation of metastable Mg with body-centered cubic structure along interface in multilayers with h of 5 nm or less. As h decreases, the hardnesses of multilayers increase and approach a maximum of ∼2.7 GPa at a few nm layer thickness. Size dependent strengthening in Mg/Nb multilayers is compared to that in Mg with various grain sizes, and Cu/Nb and Al/Nb multilayers, and strengthening mechanisms in Mg/Nb multilayers are discussed.