Microstructure and property of Ti2AlNb alloy by selective electron beam melting

Ti2AlNb based alloys is considered to be the most potential material material to replace the traditional Ni-based superalloys, because of its excellent high-temperature specific strength, creep resistance and high fracture toughness. Ti-22Al-25Nb alloy was fabricated by selective electron beam melting(SEBM), and the density of as-built samples reached 5.42-5.43 g/cm3through process optimization. The microstructure, phase evolution and mechanical property of the as-built and HIPed Ti2AlNb alloy samples were investigated. The results show that the microstructure of the as-built and HIPed samples both show the columnar crystalline structures along the deposition direction, which are all composed of B2, O and α2 phases, and the amount of O/α2 phase gradually increases from top to bottom. After HIP, the width and amount of the O/α2 phase are reduced and relatively uniform when compared with that of the as-built samples. In the bottom area, the microhardness of the as-built sample exhibits higher value of about (345.87±5.09)HV, while the hardness increases to 388.91-390.48HV after HIP. The ultimate tensile strength and elongation of the as-built sample at room temperature are (1061±23.71) MPa and (3.67±1.15)% respectively, and the ultimate tensile strength increases to (1101±23.07) MPa and the elongation reduces to 3.5% after HIP