Grain-growth Control and Single-crystal Fabrication in Metallic Additive Manufacturing Using a Flat-top Laser

Single-crystals exhibit excellent creep resistance at high temperatures and are used as high-temperature components in jet engines. Recently, the number of additive-manufactured components used in jet engines has increased. However, single-crystal structure fabrication has been difficult via laser powder bed fusion (LPBF) which is the most widely adopted process for the additive manufacturing of metallic components. In this paper, grain growth and single-crystal structure formation in LPBF using a flat-top laser with a uniform intensity distribution were described for pure Ni. In addition, a single-crystal beta-grain structure was obtained for a near-beta Ti alloy using a flat-top laser. A unique variant of the alpha phase with ⟨2-1-10⟩ along the build direction was formed during heat treatment and air cooling, which can enhance the anisotropy of the mechanical properties. Furthermore, the selection of the alpha variant was discussed.