Correlation between Ni interlayer thickness and multi-layered intermetallic compounds of Ti-6Al-4V/5Cr15MoV composite using Gleeble simulation

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Interlayer engineering is widely used in dissimilar metal joining to suppress brittle interfacial intermetallic compounds and relieve stress incompatibility, where interlayer thickness is a critical yet insufficiently understood parameter. In this work, we systematically investigate how Ni interlayer thickness ranging from 0 to 500 μm regulates the interfacial microstructure and mechanical properties of Ti-6Al-4V/5Cr15MoV dissimilar joints prepared by Gleeble simulation at 850 °C. The results reveal that a multilayered Ni-Ti intermetallic structure consisting of Ti 2 Ni, NiTi and TiNi 3 forms in all joints with a Ni interlayer. Joints with thicker Ni layers of 150 and 500 μm exhibit significantly higher mechanical strength than those with 30 and 80 μm layers. This difference is attributed to the interfacial current effect for thin interlayers during resistance heating, which generates localized Joule heating that alters diffusion kinetics and accelerates the formation of brittle Ti 2 Ni intermetallic compounds. A counter-intuitive thickness-dependent TiC formation mechanism is uncovered where thicker Ni layers promote TiC precipitation while thinner layers suppress it entirely, driven by current crowding during resistance heating. These findings offer technical guidance for optimizing dissimilar joining processes.