Environmental Engineering Reference
In-Depth Information
cury at room temperature to investigate their effect on the LME of a number of
solid metals. The results are varied. For example, zinc and gallium enhance the
embrittlement of aluminum significantly but decrease the severity in
brass. The
enhancement of severity may be a consequence of improved wetting by the liquid
metal.
α
7.2.3 Delayed Failure
Delayed failure is a generic term applied to failures under sustained load after a
period of time. In liquid metal environments the embrittlement and failure of
some metals are time-dependent. The term ''static fatigue'' is also applied to
such phenomena as the time to failure increases with a decrease in applied stress
and the stress versus time-to-fracture curve assumes the nature of a typical S-N
curve encountered in fatigue exhibiting a ''static endurance list.'' Figure 7.10
shows the delayed failure curve of Cu-2% Be alloy at room temperature wetted
with Hg-2% Na amalgam.
Attempts to induce delayed failure in notch-sensitive metals like zinc, cad-
mium, and iron-aluminum alloys in appropriate environments have not been met
with success. In these systems crack nucleation and propagation occur instantane-
ously. On the other hand, notch-insensitive aluminum-copper and copper-beryl-
Figure 7.10
Delayed failure of copper-2% Be alloy wetted with Hg-2% Na amalgam
at room temperature [8].
