Effects of Fe Contents on the Microstructure and Precipitate of Ti–Al–V Alloys Prepared by Direct Energy Deposition

Abstract

This study investigated the influence of Fe content on the microstructure and mechanical properties of Ti–6Al–4V(TC4) + 25Ti alloys prepared by low-energy-density direct energy deposition (DED) technology. With the incorporation of the Fe elements, the α-Ti phases exhibited significant changes in size and morphology, while the numerous β-Ti phases and some triclinic-Ti precipitates were retained. With the refinement of the α-Ti phase, retainment of the β-Ti phase and the presence of triclinic-Ti precipitates, the mechanical properties of DED samples can be significantly improved compared with DED TC4 alloys. The room-temperature mechanical property tests showed that the ultimate tensile strength (UTS) of 3Fe + TC4 + 25Ti achieved 1298.64 ± 5.26 MPa with an elongation of 4.82% ± 0.20%, and the maximum elongation of 1Fe + TC4 + 25Ti reached 10.82% ± 0.82% with a UTS of 1076.95 ± 11.69 MPa. The strengthening mechanism of DED Ti-Al-V-Fe alloys were further discussed, providing new insights into the microstructure control and the composition design of additive manufacturing of Ti alloys.