Process–structure relations in wire-laser directed energy deposition of binary Ti48Al alloy: Effects of substrate pre-heating and heat treatment

Titanium aluminide components fabricated by wire-laser directed energy deposition (DED-LB/M) with a high deposition rate of [Formula: see text] are investigated. To minimize oxidation during processing, deposition is conducted under vacuum with argon (Ar) shielding. The effect of substrate preheating on reducing thermal gradients and promoting room-temperature (RT) ductility was explored. Microstructures are characterized using optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and X-ray diffraction (XRD). In the as-deposited condition, the microstructure is heterogeneous, comprising large spheroidal regions of [Formula: see text]-TiAl alongside smaller equiaxed grains containing an [Formula: see text]/[Formula: see text] lamellar structure. Heat treatment at [Formula: see text] for 2[Formula: see text]h produces a fully [Formula: see text]/[Formula: see text] lamellar microstructure within very uniform, equiaxed grains (∼0.5–2[Formula: see text]mm). The interlamellar spacing is 100–400[Formula: see text]nm. In the heat-treated condition, a homogeneous hardness distribution of 300–350[Formula: see text]HV1 is obtained across the entire deposited block.