Effect of post-heat treatment on Ti2AlNb-based alloy fabricated by twin-wire alternating dual-electron beam additive manufacturing technology

Thanks to its excellent high-temperature performance and moderate density, Ti2AlNb-based alloy is considered to be a new generation of high-temperature structural material in the aerospace field. However, its application is restricted currently due to the limitations of traditional processing methods. Recently, our group first successfully prepared this alloy with an unconventional approach named wire-based in-situ additive manufacturing (AM) technology, and great mechanical performance has been obtained. The unbalanced thermal process of AM easily causes inconsistent or undesired microstructures, as well as mechanical properties. Therefore, in this study, we further carried out post-heat treatment research on the as-printed sample so as to optimize its mechanical performance. Results show that the α2-phase will precipitate from the as-deposited samples (B2/β+O) after solution treatment(ST), while all precipitates were dissolved to the B2/β-matrix when the solution temperature was 1100 °C. The aging treatment(AT) promoted a great number of O-phases precipitated and led to an increase in its proportion. With the increase in aging temperature, the tensile strength decreased (995 to 821 MPa) gradually coupling the increase of fracture strain (1.65% to 2.12%), while the aging duration time did not show an obvious effect on its performance. In addition, after proper heat treatment, the high temperature (650 °C) tensile strength of the samples was as high as 818 and 792 MPa. This research not only promotes the development of Ti2AlNb-based alloy fabricated through in-situ AM, but also facilitates its further application in the aerospace field.