Research on microstructure of TC17 titanium alloy fabricated by laser solid forming

The influences of different heat treatments on the microstructure of TC17 alloy fabricated by laser solid forming (LSF) are investigated, while the alloy in three states of as-deposited, after relief annealing and aging treatment. The results indicate that the microstructure of as-deposited sample consists of coarse columnar grains which grow epitaxially from the substrate along the deposition direction z. The microstructure within the columnar grain shows typical α+β structure. The original β grains are composed of extremely fine basketweave microstructure. And the α phase has lath morphology, its length and width are 1~3 μm and 0.1~0.2 μm, respectively. After furnace cooling (FC) annealing treatment following 1 h holding at 600 °C, the length and width of the α lath both increased while the length/width ratio decreased, but no other changes can be observed. The equiaxed α phase will be observed on the β matrix after air cooling (AC) annealing treatment following 4 h holding at 550 °C. During aging treatment, the α laths coarsen continuously as the aging time increases, whereas their length/width ratio gradually decreases. When the holding time reaches 8 h, most of the α laths are spheroidized, only a few left.