Microstructure and mechanical properties of a novel functionally graded material from Ti6Al4V to Inconel 625 fabricated by dual wire plus arc additive manufacturing

The functionally graded material (FGM) from Ti alloy to Ni alloy has potential applications in the hostile environments including high temperature and strong corrosiveness. For instance, the aerospace or nuclear industry. However, it is difficult to fabricate a FGM by the traditional methods. In this study, the dual wire + arc additive manufacturing technology was used to manufacture a functionally graded material thin walled component transitioned from Ti6Al4V to Inconel 625 using Ti6Al4V and Inconel 625 wires, with 10% composition change per gradient. The results show that the elemental distribution of the FGM component presented an excellent linear relationship with an increased component height. The FGM microstructure was changed from the bottom to top: alpha-Ti + beta-Ti -> alpha-Ti + NiTi2 -> NiTi2 -> NiTi2 + NiTi -> NiTi + Ni3Ti + (Cr, Mo) + Laves -> Ni3Ti + (Cr, Mo). The microhardness of the thin-walled component ranged from 370 HV0.2 to 843.4 HV0.2. The average ultimate compression strength and strain of vertical samples were 1390.25 MPa and 10.96%, and the fracture was a brittle cleavage one because of the formation of hard and brittle NiTi2. (c) 2022 Published by Elsevier B.V.