Alloy softening in Ni3Al polycrystals

The alloying effect of boron on localized deformation in Ni₃Al polycrystals containing 24–26 at% AI was studied using microhardness indentation. Alloy softening was observed both along the grain boundaries and in the grain interior. The softening effect decreased as the aluminium concentration increased. For alloys of near-stoichiometric composition, the maximum effect occurred at about 0.23 at% (500 wt p.p.m.) boron. A softening mechanism based on cross slip of screw dislocations was proposed.