Microstructure and mechanical properties of Ti-6Al-4V cruciform structure fabricated by coaxial electron beam wire-feed additive manufacturing

Coaxial Electron Beam Wire-feed Additive Manufacturing (CAEBWAM), which is a novel additive manu-facturing process, can produce fully dense alloy components with equiaxed & beta; grains (EG & beta;) and isotropical mechanical properties and is considered as a potential manufacturing method for large-scale complex components. However, actual complex components inevitably include bonding regions, which are similar to welded joints, in the wire-feed deposition process, and limited knowledge is available on the micro-structures and mechanical properties for this kind of regions. This work thoroughly studied the micro-structures and mechanical properties of the Ti-6Al-4V alloy cruciform structure fabricated by CAEBWAM. It was found that the microstructure at the Bonding Zone (BZ) was composed of coarse columnar & beta; grains (CG & beta;), continuous grain boundary & alpha; (& alpha;GB) phase, and coarse & alpha; laths due to a higher temperature and poor heat dissipation condition. The average width of & alpha; lath in the BZ region was larger and the hardness was lower compared with those in the EG & beta; region. Tensile properties and fracture behaviours of the tensile samples extracted at cruciform structure were examined. The fracture tended to occur at the BZ region and exhibited a mixed fracture mode with trans-and inter-granular fractures. This work will improve the un-derstanding of microstructures and mechanical properties for representative cruciform structure in wire-feed AMed components, which would be conducive to further progress of the actual complex components.& COPY; 2023 Elsevier B.V. All rights reserved.