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

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 alpha-Ti phases exhibited significant changes in size and morphology, while the numerous beta-Ti phases and some triclinic-Ti precipitates were retained. With the refinement of the alpha-Ti phase, retainment of the beta-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.