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When metallic alloys are exposed to a corrosive environment, porous nanoscale morphologies spontaneously form that can adversely affect the mechanical integrity of engineered structures. 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. 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. 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 these structures are capable of supporting dislocation-mediated plastic fracture at crack velocities of 200 m s−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. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crack speeds in monolithic nanoporous gold increase with the imposed elastic strain energy density. • Cracks in monolithic nanoporous gold can travel at speeds as high as 240 ms−1. • The fracture surface orientations found in crack penetration experiments and stress corrosion cracking are similar. • Marder's equation is used to predict the magnitude of crack penetrations and the results are in quantitative agreement with the experimentally observed behavior. Electrochemical dealloying is a corrosion process in which one elemental component of an alloy is selectively dissolved often resulting in the evolution of a bicontinuous nanoporous morphology composed of ligaments and pores. When such structures form on the surface of ductile face-centered cubic metals such as brass, stainless steels and gold-containing alloys, it has been proposed that they trigger stress-corrosion cracking as a result of their ability to support high-speed cracks that can be injected into the undealloyed parent phase alloy. Here we examine how the applied stress or stored strain energy control the dynamics of high-speed crack propagation and the relationship between the fracture plane orientation of cracks that have been injected into the undealloyed parent phase and that which forms during stress corrosion cracking of a single-crystal silver-gold alloy. In both cases, we observe exceptionally flat cleavage-like fracture surfaces, whose crystallographic orientation is determined by that of the tensile axis. We present a continuum formulation of the injection distance based upon a crack tip equation of motion that incorporates inertial effects in which the work of fracture is a decreasing function of crack speed. [ABSTRACT FROM AUTHOR]