Ductilization of Ni₃Al by macroalloying with Pd

Room temperature ductility of Ni₃Al was investigated by macroalloying with Pd which is known to have a strong tendency to substitute for the Ni site independent of the composition of the host alloy. A striking feature is that as-cast Pd-doped Ni₃Al was successfully rolled by 10-40% reduction without cracking. In addition, elongation to fracture of 11% was obtained in the recrystallized specimen with the composition of Ni₇₅Al₂₃Pd₂, whereas not entirely obtained with the composition of Ni₇₃Al₂₅Pd₂. It is shown that ductilization of Pd-doped Ni₃Al is not explained only by the electronegativity or the valency difference. Instead, it is pointed out that the ductilization of Ll₂ ordered intermetallic compounds is associated with ordering energy. The present result on the improvement in ductility of Pd-doped Ni₃Al with Al poor composition is consistently interpreted by considering degradation of ordering energy, accompanied with Pd addition and deviation of Al content from stoichiometry.