Tensile properties and microstructure of Ti-48Al-2W-0.5Si γ-titanium aluminide at temperatures between room temperature and 800℃

摘要

Five lots of theγ-TiAl alloy Ti+48Al-2W-0.5Si (at.-%) with slightly varying compositions have been examined by tensile testing and microstructure evaluation. The study has shown a large influence of the microstructure on the tensile properties.The strength levels are maintained up to temperatures of～700℃. A duplex fine grained microstructure has superior properties in comparison with a material with lower contents of aluminium and tungsten where coarse grained, nearly lamellar structuresdevelop. The microstructure is very sensitive to variations in chemical composition and heat treatment, leading to fairly high scatter in the mechanical data recorded. This scatter is smaller for the more fine grained duplex microstructure. The brittle to ductile transition temperature (BDTT) appears between 700 and 800℃ for the duplex material, while the BDTT lies above 800℃ for the nearly lamellar microstructure. The fractographic behaviour has been studied and is related to the tensile properties.