Microstructure and hardness of Ti6Al4V/NiAl/Ti6Al4V joints obtained through resistive heating

Resistive heating of Ti6Al4V/NiAl/Ti6Al4V stack resulted in formation of two strips of new phases at the filler/Ti6Al4V interface. The thinner one, growing into filler material, consists of the NiAl(Ti) phase. Parts of thicker strip, being in a contact with α-Ti grains, are filled with the coarse crystalline α2-Ti3Al phase, while those adjacent to β-Ti grains consist of α2-Ti3Al matrix with separate Ti2Ni crystallites. The hardness of Ti6Al4V plates and NiAl filler material after 6 min of processing time were measured to be ∼390HV0.05 and ∼840HV0.05, respectively, what matched the hardness of the base elements. All above indicates that the exothermic reaction of Ni/Al multilayers backed with resistive heating allowed to obtain practically defect free connection for Ti6Al4V parts.