HYDROGEN DEGRADATION OF FEMNAL ALLOYS

The effect of electrolytic hydrogen charging on FeMnAl alloys with fully austenitic and ferrite-austenite dual phase structures was studied. Little degradation of tensile properties was observed on precharged tensile specimens. With dynamic charging, the degradation of tensile properties was evident. The hydrogen-assisted cracking in the fully austenitic alloy initiated at the surface and propagated into the specimen, mainly along the grain with some surface grains fractured transgranularly. In the ferrite-austenite dual phase alloy, the crack was either along the ferrite-austenite grain boundary or through the ferrite grains. The most favorable crack path was the chain of ferrite grains situated along the austenite grain boundaries. The austenite grains were relatively resistant to hydrogen-assisted cracking.