Effect of ordinary annealing on microstructure properties of titanium alloy bars

Ordinary annealing is also known as industrial annealing, the late fire temperature is equivalent to the recrystallization beginning temperature of similar deformation titanium alloy bars, and the recrystallization temperature of some domestic grade cast titanium bars and titanium alloy bars, when the alloy structure has a certain diffusion activation energy, prompting some metastable b phase to begin to decompose completely, so that the residual stress is completely eliminated inside the casting. At the same time, it also makes the alloy maintain appropriate strength and plasticity, and obtain uniform microstructure and component energy.

According to the heat treatment specifications specified in the domestic casting titanium alloy technical conditions, the heating and cooling speed of titanium alloy bar castings during ordinary annealing should be selected to prevent castings from deformation and warping beyond the allowable range. The annealing temperature should be calculated from the lower limit of the given recrystallization temperature range. The heat preservation should be determined according to the wall thickness of the casting and the amount of furnace loading, and the relationship between the wall thickness of the titanium alloy bar casting and the late fire holding time. For castings with complex structure and large area multiple welding or repair welding, the annealing temperature should be selected at the upper limit of the given temperature range. The internal residual stress of titanium alloy bar castings can basically be completely eliminated after the delayed fire. However, for most industrial cast-effect alloys, the cooling rate during annealing has no great influence on the microstructure and properties. Therefore, an air cooling is used after the casting is annealed, and the furnace cooling is also allowed.