Tensile properties of Ti–48Al–2Cr–2Nb alloy having similarly oriented lamellae with fine lamellar spacing facilitated by suction casting

Abstract

Ti–48Al–2Cr–2Nb (at. pct) billet was prepared by suction casting into a cold steel mould, and its microstructures and mechanical properties at room and elevated temperatures were investigated. The billet featured lamellar microstructure with refined colony sizes, fine interlamellar spacing, and lamellar interfaces nearly parallel to the mould surface with a scatter angle within 30°. Benefitting from this microstructure, the billet showed excellent mechanical properties at temperatures up to 850 °C, with yield strength of 629 ± 29 MPa at ambient temperature, 549 ± 14 MPa at 650 °C, 565 ± 17 MPa at 700 °C, 475 ± 6 MPa at 800 °C and 413 ± 9 MPa at 850 °C, comparable to that of the third-generation TiAl alloys like TNM but much superior to that of most reported cast Ti–48Al–2Cr–2Nb alloys. The total fracture elongation at room temperature and 700 °C were (1.8 ± 0.2) % and (15.9 ± 3.5) %, respectively. Although the fracture at 700 °C occurred in a brittle mode, the tensile samples possessed ductile tensile elongation.