Effect of plastic deformation on the toughness behaviour of radial friction welds in Ti–6Al–4V–0.1Ru titanium alloy

A simulation trial of radial friction welding (RFW) in Ti–6Al–4V–0.1Ru titanium alloy was carried out in order to study the effect of plastic deformation (forging) on the fracture toughness of the simulated consumable ring zone (SCRZ). The simulation specimens were subjected to a comparable RFW thermal cycle and then submitted to different forging forces, producing three levels of plastic deformation. Metallographic examinations were carried out to observe the microstructural transformations generated by the thermomechanical cycle. The mechanical properties characterisation included microhardness and fracture toughness tests. The results indicated that the simulated thermomechanical cycle was successful in producing microstructures similar to those developed by a practical RFW operation, being the β-grain size of the SCRZ dependent on the degree of plastic deformation. The results also indicated that fracture toughness of the SCRZ was practically independent of the deformation level imposed.