Microstructure and properties of Ti-48Al-2Cr after thermomechanical treatment

Ingots of Ti-48Al-2Cr exhibit a strong casting texture with chemical as well as structural inhomogeneities resulting in low ductility and anisotropic formability. To improve these properties, a thermomechanical treatment is required. A two-pass upset forging method to achieve the required fine-grained equiaxed microstructure is presented. The possibilities of influencing the grain size and the corresponding mechanical properties by variation of the time and temperature in the final heat treatment are shown. The yield stress at room temperature, as given by the Hall-Petch relationship, can be controlled in the range between 360 and 495 MPa by producing grain sizes between 30 μm and 2.7 μm respectively. Tensile and compression tests were performed as a function of temperature. Typical characteristics of this material are the negative strain rate sensitivity between 200 °C and 500 °C with corresponding strain aging effects.