Elevated temperature compressive deformation behaviors of γ-TiAl-based Ti–48Al–2Cr–2Nb alloy additively manufactured by electron beam melting

Abstract

Ti–48Al–2Cr–2Nb (Ti4822) alloy was manufactured by the electron beam melting (EBM) process, and its microstructure and compressive deformation behavior at room and high temperatures (25, 600, 750, 900, and 1050 °C) were investigated. In addition, plasma-melted Ti4822 alloy was manufactured as a reference material to compare the microstructure and mechanical properties. EBM-built Ti4822 has a near-gamma structure composed of equiaxed γ phase (L10 structure) with α2 (D019 structure) phase at the interface of γ phase, whereas plasma-melted Ti4822 has a fully lamellar structure. Temperature-dependent compression tests identified that EBM-built Ti4822 has relatively low yield strength in all temperature ranges compared to plasma-melted reference material. However, in the case of ductility, EBM-built Ti4822 has higher fracture strain compared with plasma-melted Ti4822. The reason for this behavior is the microstructural differences found between EBM-built and plasma-melted Ti4822. In the high-temperature compressive results, yield stress anomaly (YSA) phenomena occurred in a certain temperature range with both alloys. The room temperature deformed microstructure shows that EBM-built Ti4822 accommodated deformation by dislocation glide and twinning, while plasma-melted Ti4822 could not fully accommodate the deformation. In addition, dynamic recrystallization (DRX) occurred at above 900 °C in the EBM-built Ti4822, and above 750 °C in the plasma-melted Ti4822, suggesting that different DRX behavior appeared in high temperature deformation. Based on the above findings, this study further analyzed the correlation between the microstructure and the room- and high-temperature deformation mechanism of EBM-built Ti–48Al–2Cr–2Nb.