Control of the microstructure and mechanical properties of GTA-based wire arc additive manufactured TiAl alloys using post heat treatment

The control of the microstructure and mechanical properties of deposited TiAl alloy with Al content of 45 at.% using heat treatment was studied. Based on the Ti-Al binary phase diagram, four heating temperatures were used: 1 080, 1 200, 1 270 and 1 350 ℃. Furnace cooling was applied after holding for 1 h. It was found that with the increase of the heating temperature, the segregation is gradually eliminated, and the γ phase on the grain boundary decreases. The microstructure changes from two-state structure to full lamellar structure, and the lamellar colony size increases gradually. Preservate heat at 1 350 ℃ for 5, 30 min and 1 h, respectively. It was found that the lamellar colony coarsened with the extension of holding time. Based on the single-stage heat treatment, the cyclic heat treatment process was proposed. The deposited parts were heated repeatedly between 900 to 1 200 ℃ and cooled after short-term insulation. The components with fine lamellar structure were obtained, whose hardness reduces, and the compressive strength and compression ratio both increase.