Microstructure evolution, deformation behavior and processing performance of TNM TiAl alloy

The hot compression test, with a true strain of 0.9, was carried out at a temperature of 1100–1250 °C and a strain rate of 0.001–1 s⁻¹ by a Gleeble3800 thermal simulation testing machine for the as-cast TNM alloy. The stress–strain curves were recorded to measure the deformation resistance and deformation uniformity of the whole specimens, and the microstructure was analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) from the perspectives of the extent of recrystallization and the orientation and size of the grains. At lower strain rates, the strain is more uniform within the specimen. At higher temperatures, a complete recrystallization microstructure showing an equiaxed nearly lamellar (NL) structure with a weak texture can be obtained at a low strain rate, and a microstructure showing an elongated fine-grained NL structure without texture can be obtained at a high strain rate. The deformation mechanisms were analyzed, and the processing parameters were optimized by constructing empirical hot processing maps. The parameters 1200–1250 °C and 0.1–0.01 s⁻¹ are recommended for deformation to obtain a uniform fine grain structure economically without cracking of the specimen.