MICROSTRUCTURE AND PROPERTIES OF CAST Ti-46Al-8Ta ALLOY

摘要

The microstructure and properties of so called "air-hardenable" intermetallic Ti-46Al-8Ta (at.%) alloy are studied. Primary solidification phase, solidification path and solid phase transformations are evaluated using quenching during directional solidification experiments and Jominy end quench tests combined with microstructural analysis. Mechanical properties of specimens with lamellar and convoluted α_2(Ti_3Al)+γ(TiAl) microstructure such as tensile, compression and creep are studied. Creep properties such as minimum creep rate, time to 1 % creep deformation, fracture time, kinetics of creep deformation and creep fracture are presented and compared to other TiAl-based alloys developed for industrial applications. Long-term high temperature microstructural stability during ageing, creep at constant load and creep at thermal cycling conditions are presented. The distribution, size and volume of cavities and cracks formed during creep are assessed by non-destructive X-ray 3D computed tomography. Based on the achieved experimental results, the potential of this new alloy to fulfill industrial specifications is discussed.