ENVIRONMENT-ASSISTED CRACKING OF FE-32-PERCENT MN-9-PERCENT AL-ALLOYS IN 3.5-PERCENT SODIUM-CHLORIDE SOLUTION

The stress corrosion cracking (SCC) behavior of four austenitic Fe-32% Mn-9% Al alloys containing approximate to 1 wt% carbon was studied. All of the four alloys were susceptible to SCC in room temperature and 160 degrees C NaCl solution. SCC was enhanced by applying an anodic potential. The crack path was transgranular, and cleavage-like regions were observed on the fracture surface. The corrosion-assisted microcleavage model proposed for the transgranular SCC behavior of face-centered cubic (fcc) materials very likely was the operating SCC mechanism of the austenitic Fe-Mn-Al alloys. Adding 1.23% Mo or 1.27% Si to the austenitic Fe-32% Mn-9% Al alloys did not change the SCC mechanism and crack paths. Adding 1.27% Si made the alloys more susceptible to SCC, but no such effect was observed with the addition of 1.23% Mo. All four alloys studied were susceptible to hydrogen embrittlement (HE) in 3.5% NaCl solution at large cathodic applied potentials, and the crack paths were intergranular. The addition of Mo, Cr, or Si in the alloy displaced the potential at which HE occurred to more cathodic values.