Abstract Scope |
Nanoporous metal is material with sponge-like structure, composed of continuously connected ligament and pore at nanoscale, which gives low density and high surface-to-volume ratio. These properties provide the advantages of application for catalyst, actuator, and sensor. However, though gold is ductile metal at bulk scale, brittle fracture occurs in nanoporous gold (np-Au) by stress concentration on pore surface and catastrophic crack propagation through grain boundaries. In this study, we focus on designing hierarchical grain boundaries as detoured crack propagation path.
We perform cyclic hot-rolling and intermediate annealing on Au-Ag alloy. Hierarchical grain structure evolves at micron scale by interaction of shear band and deformation twin, and hierarchical np-Au forms as Ag is selectively etched by free-corrosion dealloying in nitric acid. Fracture toughness, KⅠc and KJc is investigated on coarse grained, fine grained, and hierarchical grained np-Au, and we discuss effect of grain boundary structure on fracture toughness and crack propagation. |