Microstructures and tensile properties of Ti2AlNb and Mo-modified Ti2AlNb alloys fabricated by hot isostatic pressing

Abstract

The Ti2AlNb and Mo-modified Ti2AlNb alloys were fabricated by hot isostatic pressing, and then underwent annealing treatment at 800 °C for 1, 2 and 3 h respectively. To evaluate the tensile properties of the two kinds of alloys, tensile tests were conducted at ambient temperature and 650 °C in this study. For the Ti2AlNb alloy, the room-temperature ultimate tensile strength (UTS) was 700–900 MPa, and the highest elongation to failure (εf) reached 6.2% after aging for 2 h at 800 °C. Since the Mo addition promoted the precipitation of the coarse B2+O colony structure near the grain boundary, the Mo-modified Ti2AlNb alloy exhibited decreased UTS and εf at room temperature. As for the high-temperature performance of both the Ti2AlNb and Mo-modified Ti2AlNb alloys, the UTS reached approximately 700 MPa and the εf exceeded 3.0%. Meanwhile, the two kinds of alloys presented the same tendency that both the high-temperature UTS and εf increased firstly and then decreased as the aging time increased. Among them the specimens after aging at 800 °C for 2 h for both alloys acquired the highest UTS and εf. Moreover, the Mo-modified alloy exhibited a better high-temperature ductility than that at room temperature, which is associated with the B2↔O phase transformation during the loading at 650 °C. The Mo addition effectively refined the lath of the precipitates in the grain and the grain size of the matrix, and it induced abundant dislocations. Thus, the Mo-modified Ti2AlNb alloy aged for 1 and 3 h exhibited superior high-temperature mechanical properties than those of the Ti2AlNb alloy.