Microstructure and Mechanical Properties of TiAl Alloy Fabricated by Laser Melting Deposition

Complex shaped TiAl alloy components can be manufactured by laser additive manufacturing technology, further expanding the engineering applications of this lightweight high-temperature alloy in the aerospace field. However, there is currently limited research on the intrinsic relationship among the laser melting deposition process, microstructure, and properties of TiAl alloys. TiAl alloy specimens with good macroscopic quality were prepared by laser melting deposition using Ti-48Al-2Cr-2Nb alloy powder as raw materials. The microstructure, phase composition, hardness distribution of the deposited layer, and room temperature mechanical properties of the deposited specimens were studied under optimized process parameters. The results show that the microstructure of the deposited layer mainly consists of a large number of gamma-TiAl phases and a small amount of alpha(2)-Ti3Al phases; the microstructure of the deposited sample exhibits a layer characteristics formed by columnar crystals, equiaxial crystals, cytosolic crystals, and laths structure, and the grain refinement in the microstructure of the deposited layer is obvious. The hardness distribution of the deposited layer ranges from 537 HV0.3 to 598 HV0.3, and the Vickers hardness at the bottom is higher than that at the middle and the top. The ultimate compressive strength of the TiAl alloy specimens is (1545 +/- 64) MPa at room temperature, with a compressive strain of (17.68 +/- 0.07)%, and the ultimate tensile strength along the scanning direction of the laser is (514 +/- 92) MPa at room temperature, with an elongation of (0.2 +/- 0.04)% after break; the ultimate tensile strength along the building direction is (424 +/- 114) MPa, with an elongation of (0.15 +/- 0.07)% after break. The tensile fracture morphology of TiAl alloy specimens exhibits quasi cleavage fracture characteristics. By optimizing the scanning strategy and assisting with subsequent heat treatment, it is expected to improve the uniformity of alloy structure and the anisotropy of mechanical properties.