Abstract: As a quaisi-brittle material, TiAl alloys are very sensitive to notches since their existence may cause fracture which may reduce seriously the service performance of the alloy. Therefore it is necessary to study the fracture properties of TiAl alloys with notches. In this article, a study is conducted on the influence of temperature and tensile rate on the notch fracture properties of Ti-48Al-2Cr-2Nb with near full lamellar microstructures using the combined tensile specimens with notches. The study indicates that TiAl alloys possess notch sensitivity at room temperatures, but that the notch sensitivity of TiAl alloys is reduced at higher temperatures. When the temperature reaches 800 ℃, the alloys exhibit little sensitivity to notches. The plastic deformation of TiAl alloys may be caused by dislocation sliding and mechanical twinning at lower temperatures, while at higher temperatures it may be caused by dislocation climbing controlled by diffusion. The study also indicates that TiAl alloys possess no notch sensitivity at lower tensile rates at 200 ℃, while they become sensitive as the tensile rate increases.

Key words: TiAl, fracture properties, notch sensitivity, temperature, tensile rate