Microstructure distribution characteristics of LMD-WAAM hybrid manufacturing Ti-6Al-4V alloy

Abstract

Laser melting deposition (LMD) and Wire arc additive manufacturing (WAAM) are representative metal additive manufacturing (AM) technologies. To explore the feasibility of using the LMD-WAAM hybrid process to fabricate large and complex components, a preliminary investigation of Ti6Al4V was conducted. In this study, a WAAMed sample was used as a substrate for the LMD process at different laser powers. The effects of laser power on the grain evolution and mechanical properties of the Ti6Al4V alloy were studied. The results indicated that different thermal histories formed a graded microstructure from the LMD to the WAAM zones. The Electron backscatter diffraction texture intensity of the α phase gradually increased from the remelting zone (RZ) to the top-LMD zone and from the WAAM zone to the heat-affected zone. In the LMD zone, the length of the acicular α decreased and the lamellar α content increased with increasing laser power. Ductile fracture characteristics were apparent with few cleavage fractures and pore defects, which led to different fracture locations. Further, the microhardness of the interface zone exhibited a peak because the microstructure of the RZ was fine, leading to a higher microhardness.