A novel Ni–Co–Al multi-principal filler wire for inhibiting Fe–Ti intermetallic compounds in welding CP-Ti/Q345 bimetallic sheets

Abstract

In this work, a novel Ni–Co–Al multi-principal wire was used as only one type of filler material to finish the joining of TA1/Q345 bimetallic sheets by in situ preparation of high-entropy materials in the weld zone (WZ). The results indicated that a good weld formation could be achieved by using the Ni–Co–Al wire. The thermodynamic environment with high mixing entropy (ΔS_mix) and low mixing Gibbs free energy (ΔG_mix) in the WZ could be created by the Ni–Co–Al wire and the elements introduced from base metals. It could efficiently inhibit the formation of Fe–Ti IMCs and promote the solid-solution structures of FCC and BCC in the WZ. Fe–Ti IMCs were only presented in the transition zones on the TA1 flyer layer as well as a narrow region of the WZ within ∼30 μm away from the Q345/WZ interface, where the ΔG_mix was higher than the ΔG of Fe–Ti IMCs.