Potential-dependent dynamic fracture of nanoporous gold

When metallic alloys are exposed to a corrosive environment, porous nanoscale morphologies spontaneously form that can adversely affect the mechanical integrity of engineered structures(1,2). This form of stress-corrosion cracking is responsible for the well-known 'season cracking' of brass and stainless steel components in nuclear power generating stations(3,4). One explanation for this is that a high-speed crack is nucleated within the porous layer, which subsequently injects into non-porous parent-phase material(5). We study the static and dynamic fracture properties of free-standing monolithic nanoporous gold as a function electrochemical potential using high-speed photography and digital image correlation. The experiments reveal that at electrochemical potentials typical of porosity formation(6) these structures are capable of supporting dislocation-mediated plastic fracture at crack velocities of 200 ms(-1). Our results identify the important role of high-speed fracture in stress-corrosion cracking and are directly applicable to the behaviour of monolithic dealloyed materials at present being considered for a variety of applications.