Effect of Yttrium Addition on Microstructures and Room Temperature Tensile Properties of Ti-47 Al Alloy

The microstructures and room temperature tensile properties of a series of Ti-47 Al-x Y (x = 0%, 0. 1%, 0.3%, 0.5%, 0.7% and 1.0% (atom fraction)) were investigated systemically. Results show that both the grain size and lamellar spacing decrease remarkably with the increase of Y content. When the content of Y is greater than 0.1%, most of the Y elements accumulate along the grain boundaries and some fine particles are uniformly dispersed within the grains in the form of YAl2 compound because of the low solubility and segregation of Y in TiAl alloys. Grain-boundary segregation of Y element is more prominent with the increase of Y addition. Good tensile properties are obtained when Y addition ranges from 0.3% to 0.5%. The refinement of grain and lamellar structures and dispersion of YAl2 within the grains contribute to the improvement of tensile properties. On the other hand, for high Y-added alloys (over 0.5% Y), tensile properties are obviously deteriorated due to brittle cleavage fracture of the coarse YAl2 network.