Effects of Sc addition on the microstructure and tensile properties of Ti–6.6Al–5.5Sn–1.8Zr alloy

The effects of Sc additions on the microstructure and tensile properties of Ti–6.6Al–5.5Sn–1.8Zr-based alloys have been investigated. The results indicated that Sc acts as α-stabilizer in the studied alloy system. The grain sizes of as-cast and forged alloys were refined significantly by Sc additions. With increasing Sc addition, a large number of Sc5Sn3 and oxides are formed. The formation of brittle α2-Ti3Al precipitates during long-term aging treatment is suppressed by high content of Sc addition. The Sc addition increases the solid solution strengthening; meanwhile, the formation of Sc5Sn3 and oxides plays a role in grain refinement and dispersion strengthening. Therefore, it has been found that both room temperature and high temperature strengths are gradually improved, whereas the ductility is decreased with increasing Sc addition.