Effect of heat treatment on microstructure and fracture toughness of Ti-6Al-4V alloy by forging-additive hybrid manufacturing

The technology of forging-additive hybrid manufacturing can provide an effective solution for innovative structural fabrication, which has combined the advantages of forging in efficiency and additive manufacturing in flexibility. In this study, laser-based directed energy deposition (DED) technology was employed to deposit bulk samples on a forged Ti-6Al-4V substrate. Microstructures evolution and strengthening mechanism of fracture toughness on the bonding zone under different heat treatments were studied. Not like fine alpha was favorable to enhance the value of microhardness, wide alpha laminar or wide alpha cluster containing thick lath alpha can impede crack propagation effectively, a regression formula was acquired between alpha lath width and fracture toughness. Therefore, when the heat treatment was implemented over the beta-transus temperature (T-beta), sample's microstructure was transformed into widmanstatten structure which retarded the crack propagation, and attained the highest fracture toughness compared with other heat treatment processes.

Automated summary

Forging-additive hybrid manufacturing technology combines the efficiency of forging and the flexibility of additive manufacturing, providing an effective solution for innovative structural fabrication. Using laser-based directed energy deposition technology, this study investigated the microstructure evolution and strengthening mechanism of fracture toughness in the bonding zone under different heat treatments.