Manufacturing of a nanosized TiB strengthened Ti-based alloy via electron beam powder bed fusion

Abstract We manufactured a Ti-based alloy via electron beam powder bed fusion (PBF-EB) and systematically investigated its microstructure and mechanical properties. We compared its properties with those of a conventionally forged alloy via electron backscattered diffraction, high-angle annular dark-field scanning transmission electron microscopy observations, and tensile tests. The formation mechanism, orientation relationship with the matrix, and crystal structures of the nanosized TiB particles were verified. The formation of nanosized TiB particles was mainly attributed to high cooling rates during PBF-EB manufacturing. In addition, the segregation of the solute Zr and Si atoms into the α-phase/TiB interface restricted TiB precipitate growth, which contributed to the formation of fine TiB particles in the alloy manufactured via PBF-EB. The orientation relationships between the TiB particles and α-phase in the PBF-EB-manufactured alloy are different from those in the hot-forged alloy. Moreover, for the first time, the simultaneous existence of the B27 and twinned B27 structures was verified in the nanosized TiB particles. Our study provides general guidelines for the manufacturing of materials strengthened by refined precipitates using PBF-EB or other additive manufacturing methods.