Effect of material gradation strategy on the microstructure and mechanical properties of directed energy deposition Inconel 718/CuCrZr compounds

Laser powder directed energy deposition (LP-DED) is an additive manufacturing (AM) process that enables the production of multi-material components with no limitations in gradation strategy and direction. Although performance variations are expected in multi-material systems depending on the material design, a detailed understanding of the effect of material gradation strategy on the microstructural and mechanical properties of such components is still missing. Therefore, this paper aims to address, for the first time, how the sequence and direction of material alteration affect the formation and properties of the interface. Inconel 718 and CuCrZr alloys were employed to carry out detailed microstructural, mechanical, and electrical analyses in order to establish a relationship between the gradation direction and the corresponding properties. The results showed that the sequence of material deposition has a significant effect on the formation of the interface, grain structure, and microhardness variation along the interface. The gradient transition enabled a gradual microstructural and mechanical transition, which provided better control over the material performance compared to the directly transitioned counterparts. The obtained findings underline the critical role of material gradation in governing interfacial phase evolution and mechanical performance in LP-DED Inconel 718/CuCrZr systems, providing design guidelines for reliable multi-material AM of high-performance structural applications.