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

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 776; p. 139043
• Main Authors: Zhang, Yaran, Liu, Yongchang, Yu, Liming, Liang, Hongyan, Huang, Yuan, Ma, Zongqing
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 03.03.2020; Elsevier BV
• Subjects: Aging; Aging (metallurgy); Alloys; Ambient temperature; Elongation; Fracture; Grain boundaries; Grain size; Heat treating; Hot isostatic pressing; Intermetallic compounds; Mechanical properties; Mo addition; Molybdenum; Phase transitions; Precipitates; Room temperature; Tensile properties; Tensile strength; Tensile tests; Thermal stability; Ti2AlNb alloys; Ultimate tensile strength; Mechanical properties; Mo addition; Fracture; Ti2AlNb alloys; Tensile strength
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2020.139043

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.