Abstract: Effect of double annealing process on microstructure and mechanical properties of the TC18 alloy quasi-β forged piece was investigated. The results show that with the increase of first annealing high-stage temperature, lamellar α phases separate and spheroidize, the plasticity decreases slightly. With the decrease of cooling time from high-stage temperature (830 ℃) to middle-stage temperature (750 ℃) and with the increase of first annealing middle-stage temperature, the strength increases but the plasticity and the fracture toughness decrease. With the increase of first annealing middle-stage temperature, the quantity of untransformed β microstructure and dispersed secondary α phases increases. The second annealing temperature has a great effect on the morphology and content of the secondary α phases. With the increase of second annealing temperature, the secondary α phases aggregate and grow, and its dispersion degree decreases, the strength of the forging decreases, while the plasticity and fracture toughness increase.

Key words: TC18 alloy forged piece, quasi-β forging, double annealing, microstructure, mechanical properties