Effect of Beta Phase on Room to High Temperature Mechanical Properties of As-Cast Gamma Titanium Aluminide

The microstructure and room to high temperature mechanical properties of binary, Ti-48at.%Al and beta phase contained, Ti-48at.%Al-4at.%Cr as-cast gamma titanium aluminide were investigated. Microstructural examination indicates that there is no significant difference between the microstructure of both alloys except the formation of beta phase in Ti-48at.%Al-4at.%Cr. Room temperature fracture strength and ductility were obtained from tensile test. The tensile fracture surfaces were examined using scanning electron microscope in secondary electron mode. Constant load tensile creep tests were performed at 600-800 degrees C with initial stresses from 150 to 180 MPa. Mechanical properties of Ti-48at.%Al-4at.%Cr and Ti-48at.%Al were compared. The role of beta phase was discussed. It is concluded that beta phase is sensitive to temperature and detrimental at both room and high temperature. However, it has a positive effect on mechanical properties at intermediate temperatures.