Effect of forging routes on the microstructure and mechanical properties of newly-developed Ti-44Al-5.5Nb-0.5W-0.5Cr-0.3Si-0.1C alloys

Abstract

In this study, the effects of forging routes on the microstructure and tensile properties of Ti-44Al-5.5 Nb-0.5 W-0.5Cr-0.3Si-0.1 C (at%) alloys was comparatively investigated. Results showed that the bare ingot forged at 1400 ℃ (BH) exhibited refined lamellar colonies with narrow lamellar spacing. In contrast, dynamic recrystallized γ grains and lamellar structure with thick lamellar spacing formed in the canned sample deformed at 1320 ℃ (CA). In addition, the heat-treated BH-HT sample showed fully recrystallized texture, while the lamellar structure in the CA-HT presented a preferred orientation, i.e., lamellar interfaces were parallel to rolling direction (RD). The mechanical properties of the CA-HT sample test results showed superior room-temperature ductility of 1.68 % and tensile strength of 515 MPa at 950 ℃ due to the lamellar orientation alignment to tensile direction. According to the temperature drop calculation results, both BH and CA forging routes exhibited rapid cooling rates. The initial microstructure at the pre-heating temperature was maintained until a hot deformation sequence was initiated. Therefore, the BH route could be performed in the α+β region, while the CA route could be carried out in the α-forging condition with the 1101̅12 γ texture.