Reactive resistance welding of Ti6Al4V alloy with the use of Ni(V)/Al multilayers

The freestanding Ni(V)/Al multilayer foil was applied as a filler material in order to join Ti6Al4V alloy with the use of reactive resistance welding (RRW) technique. Present investigations, performed with the use of transmission electron microscopy (TEM) method, allowed to show that an application of high current (I = 400 A for 2 min in vacuum conditions similar to 10(-1) mbar) transformed the Ni(V)/Al multilayers into fine grain (< 300 nm) NiAl phase. It also showed that the RRW process led to the formation of firm connection with nanoporosity limited only to the original contact plane between base material and the foil. Simultaneously, the formation of a narrow strip of crystallites of Ti3Al intermetallic phase elongated along the joint line (average size of similar to 200 nm) was observed. The base material was separated from the joint area by a layer of up to similar to 2 mu m thickness of nearly defect free alpha-Ti and beta-Ti grains from a heat affected zone (HAZ). The performed experiment proved that Ni(V)/Al multilayer could serve as a filler material for joining of Ti6Al4V alloys even without additional solder layer. (C) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim