The corrosion and stress corrosion cracking (SCC) susceptibility of an A-Mg
alloy, AA5083, has been shown to depend on the precipitation of the Mg-ric
h beta phase, (Al3Mg2), but not the enrichment of elemental Mg at grain bou
ndaries to an enrichment ratio of 1.4. These results were determined by mea
suring the progress of Mg enrichment at grain boundaries for increasing the
rmal-treatment times, using auger electron spectroscopy (AES) of grain boun
daries exposed by fracture within the spectrometer and by analytical electr
on microscopy (AEM) of thin foils. The progress of the beta phase precipita
tion was followed by AEM and scanning electron microscopy (SEM), for the sa
me thermal treatment times. The lack of a Mg-segregation effect on SCC was
demonstrated by results obtained with X-ray photoelectron spectroscopy (XPS
) analysis of Mg-implanted Al following in-situ electrochemical tests and S
CC tests, while the dominance of beta phase precipitation was demonstrated
by electrochemical analysis and SCC testing. Crack-growth tests of alloy AA
5083 demonstrated faster cracking at potentials anodic to the open circuit
potential (OCP) with no increase at potentials cathodic to the OCP.