Microstructure control and creep behavior of Ti-47Al-6Nb-0.1C alloy by directional solidification

Newly designed Ti-47Al-6Nb-0.1C at.% alloy was directionally solidified by cold crucible under 45 kW at the growth rate of 5-16.67 μm/s. The macro/microstructure evolution, room-temperature tensile property and creep behavior are investigated. The results show that this alloy was well directionally solidified by cold crucible at the growth rate of 5-11.67 μm/s, and they display primary β solidification at this growth-rate range. It is also found that the lamellar spacing is mainly controlled by growth rate, and the lamellar spacing decreases with the increasing of growth rate according to relationship d=1751V−0.58. Moreover, the extent of microsegregation increases with the increasing of growth rate, and thus the effect of microsegregation on creep behavior is discussed. After controlling directional solidification process at growth rate of 5-8.33 μm/s, this alloy exhibits good creep properties with creep life more than 800 h at 800 °C/200 MPa, and the acceptable room-temperature tensile property with yield strength 436-452 MPa and elongation 1.62-1.68%.