Embrittlement of CU-17Al Alloy By Liquid Mercury

Abstract

<p> The role of plastic deformation in the initiation and propagation of cracks in Cu-17Al alloy embrittled by liquid mercury has been studied. It is proposed that extensive plastic deformation and work hardening must occur at the crack-tip during propagation in order to raise the local flow stress to a critical level at which the maximum normal stress is equal to the cohesive strength. A crack initiation mechanism is proposed involving grain boundary diffusion enhanced by the stress concentration at the head of dislocation pile-ups at the grain boundary. Micro-cracks are formed at the weakened grain boundary and a period of stable crack growth made over a period of increasing applied stress may be necessary before the crack is long enough to become unstable.</p>