Effect of Heat Treatment on Microstructure and Properties of Ti6321 Alloy Slab with Different Microstructures

The effects of slab microstructure type and heat treatment on microstructure and properties of Ti6321 alloy were studied by mechanical properties test, OM and SEM. The results show that slab microstructure type of Ti6321 alloy has a significant effect on the microstructure and properties of the rolling sheet. By the same rolling process (the first fire: 980 degrees C start rolling, finish rolling temperature 800 degrees C, epsilon=70%, and the second fire: 995 degrees C start rolling, finish rolling temperature 800 degrees C, epsilon=50%), equiaxed slabs form bimodal slabs, and Westernized slabs form equiaxed slabs. After annealing below (alpha+beta)/beta phase transformation point, the longitudinal and transverse yield strength and tensile strength of the plate made of equiaxed slab are higher than those of the corresponding direction of the plate made of Widmanstatten slab, while the elongation and impact energy are opposite. With the increase of annealing temperature, the yield strength and tensile strength of the sheets prepared with different slab structures decrease slightly, while the impact energy increases sharply. When annealed above (alpha+beta)/beta transformation point, the tensile properties and impact work of the two alloys decrease significantly. During the annealing process in the alpha+beta two-phase zone, the sensitivity of the initial alpha phase to temperature is higher than that to the holding time of annealing. With the increase of temperature, the content of primary alpha phase decreases sharply, while the content of secondary flake alpha phase increases obviously. The suitable annealing process range of Ti6321 alloy is (940 similar to 980) degrees C/(2 similar to 3 h).