A two-stage lightweighting
Dealloying allows voids to be created in metals, decreasing the weight of the material. However, when the solid fraction is below about 30%, the mechanical properties rapidly degrade. Shi et al. discovered that two dealloying steps allow for the creation of a silver-gold alloy with a solid fraction as low as 12%. Unexpectedly, this process does not degrade the mechanical properties while allowing for large samples to be synthesized. The strategy should be applicable to other alloy systems, providing a pathway for creating strong and lightweight materials.
Science, this issue p. 1026
Structural hierarchy can enhance the mechanical behavior of materials and systems. This is exemplified by the fracture toughness of nacre or enamel in nature and by human-made architected microscale network structures. Nanoscale structuring promises further strengthening, yet macroscopic bodies built this way contain an immense number of struts, calling for scalable preparation schemes. In this work, we demonstrated macroscopic hierarchical network nanomaterials made by the self-organization processes of dealloying. Their hierarchical architecture affords enhanced strength and stiffness at a given solid fraction, and it enables reduced solid fractions by dealloying. Scaling laws for the mechanics and atomistic simulation support the observations. Because they expose the systematic benefits of hierarchical structuring in nanoscale network structures, our materials may serve as prototypes for future lightweight structural materials.