Hydrogen effects on slip character and ductility in NiCo alloys

Abstract

Nickel-cobalt binary alloys containing 45, 55 and 65 wt.% Co were annealed to a constant grain size and deformed in compression to produce slip lines. Strains were 2.5 and 5% for surface slip lines, and 2.5% for “interior” slip lines. Some specimens were also pre-charged with hydrogen from the gas phase prior to testing. The waviness of “interior” slip lines in uncharged specimens decreased with increasing Co content, i.e. decreasing stacking fault energy, as would be expected, but in the presence of hydrogen no dependence on Co content was observed. Hydrogen somewhat reduced the waviness of slip lines in these alloys, but mostly for surface slip lines. The results have implications for deformation-related concepts of hydrogen effects on materials.