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 Sc 5Sn 3 and oxides are formed. The formation of brittle α 2-Ti 3Al 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 Sc 5Sn 3 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.
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