A promising strategy of multicomponent alloy intermedium for enhancing the mechanical performance of inertia friction welding joints of Inconel 718 alloys

A strategy of using multicomponent alloy (MCA) intermedium for inertia friction welding of IN718 alloys was proposed in this work. Exceptional metallurgic bonding was attained between the IN718 and non-equiatomic CoCrNi–AlTa MCA layer, and the as-received weld joint was absent of any defects like micro-cracks or voids. Compared with the counterpart without an intermedium layer (∼530 MPa), the yield strength of the IN718-MCA weld joint was increased to ∼610 MPa. Moreover, by conducting a two-step ageing treatment, the yield strength of the weld joint was further improved to over 1360 MPa with prominent strain hardening behavior. Noteworthily, the fracture along the interface boundary between the two materials initially observed in the unaged weld joint was fully eliminated, indicating that the ageing treatment efficiently improved the bonding of the interfacial region and further enhanced the reliability of the weld zone. Moreover, the significant strengthening effect of the aged dissimilar weld joint was found to originate from the enhanced atomic diffusion and extra back-stress hardening from geometric necessary dislocations (GNDs) produced within the interfacial regions, as well as the high density of nano-sized dispersive precipitates (for IN718) and ordered structures (for MCA) generated in the alloy matrix at elevated temperatures. The result verifies that the present strategy of adding an MCA intermedium layer can efficiently improve the mechanical performance of the weld joint for IN718 alloys, which is promising for real applications in aerospace engineering.