Effects of extrusion deformation on microstructure, mechanical properties and hot workability of β containing TiAl alloy

Hot extrusion was performed on a Ti-42Al-9V-0.3Y alloy at 1200-1325 °C to explore effects on mechanical properties and hot workability. The microstructure after hot extrusion was analyzed, tensile tests were conducted, and hot workability was assessed. Three types of microstructures resulted from extrusion at increasing temperature, including a dual-phase microstructure (DPM), a bi-lamellar microstructure with retained gamma phase (BLMG), and a bi-lamellar microstructure (BLM). Hot extrusion of the TiAl alloy in the range of 1275-1325 °C produced the BLM microstructure, yielding superior comprehensive properties. The predominant fracture mode was transgranular cleavage fracture in the DPM, translamellar cleavage and delamination in BLM, and mixed fracture in BLMG. Aggregation of the YAl2 phase accelerated the fracture of the as-extruded alloy. As-extruded Ti-42Al-9V-0.3Y alloy exhibited excellent high-temperature mechanical properties and hot workability, demonstrating the feasibility of precision forming TiAl alloy components by conventional hot forging with nickel-based alloy dies.