Room and elevated temperature mechanical properties of PM TiAl alloy Ti-47Al-2Cr-2Nb

A TiAl alloy powder with the composition Ti-47Al-2Cr-2Nb (at.%) was prepared by rotary atomization, followed by hot-extrusion and subsequent heat-treatments to produce refined lamellar structures and fine duplex structures. The mechanical properties of the TiAl alloy were determined at temperatures to 1000°C in air, and the microstructures were characterized by TEM, SEM, and electron microprobe analyses. The alloy with the refined lamellar structure showed excellent mechanical properties at both room and elevated temperatures. It exhibited a plastic strain of 1.4% and a yield strength of 971 MPa (140.9 ksi) at room temperature. The yield strength remained approximately constant up to 800°C and decreased to 577 MPa (83.7 ksi) at 1000°C. The transverse fracture toughness, estimated by three-point bend testing of chevron-notched specimens at room temperature, was 22.4 MPa √m. The refined lamellar structure contained long and straight alternating α₂ and γ platelets with an extremely fine interlamellar spacing (0.1 μm) and α₂-to-α₂ spacing (0.22 μm). The mechanical properties of the alloy have been correlated with the unique microstructures developed by hot extrusion.