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.