Effects of multi-step heat treatment on the microstructure, segregation and property of a directional solidified Ti-45.5Al-3Nb-0.11C-0.3Si alloy produced by electromagnetic confinement

Multi-step heat treatments and corresponding room temperature tensile tests of Ti-45.5Al-3Nb-0.11C-0.3Si alloys with directional full-lamellar microstructure are performed. Effects of the temperature and the number of experimental cycles on the microstructure, segregation and property of the alloy are studied. In full-lamellar microstructure, the thickness and the proportion of the alpha lamellae are reduced and the lamellar decomposition phenomenon increases as the temperature rises. When the temperature exceeds 1070 degrees C, particle phases begin to precipitate along the alpha/gamma interface. Results show that there are three different stages in the content and segregation changes of each element in different processes, and changes in Ti and Al are linear and uniquely related to the initial composition. With different processes, the tensile properties at room temperature increase first, then decrease and slowly climb at last. The elongation increases up to 2.69 times and the tensile strength increases to 2.45 times after appropriate heat treatment.