Effect of Yttrium Addition on Microstructures and Room Temperature Tensile Properties of Ti-47A1 Alloy

摘要

The microstmctures and room temperature tensile properties of a series of Ti-47Al-xY ( x = 0 percent, 0. 1 percent, 0.3 percent, 0.5 percent, 0.7 percent and 1.0 percent (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 percent, most of the Y elements accumulate along the grain boundaries and some fine particles are uniformly dispersed within the grains in the form of YAl_2 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 percent to 0.5 percent . The refinement of grain and lamellar structures and dispersion of YAl_2 within the grains contribute to the improvement of tensile properties. On the other hand, for high Y-added alloys (over 0.5 percent Y) , tensile properties are obviously deteriorated due to brittle cleavage fracture of the coarse YAl_2 network.