Constant extension rate tests have been carried out on copper single crystals in a sodium nitrite solution, using an applied potential to accelerate the cracking. Crack velocities up to 30 nm per second were obtained at 30 °C. The stress-corrosion fracture surfaces are cleavage-like, with curved striations parallel to the crack front. If the dynamic straining is stopped, the cracks apparently stop growing within about 20 /μm. The steps between adjacent flat facets are more energy-absorbing than in a-brass, providing a possible explanation for the importance of dynamic strain. Simultaneous acoustic emission and electrochemical current transients have been measured, and suggest that cracking proceeds by discontinuous cleavage.
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