Titanium alloy heat treatment – heat treatment

The basic heat treatment: heat treatment method of titanium, titanium industrial pure titanium is single-phase alpha type organization, in spite of above 890 ℃ alpha beta polymorphism of change, but due to the phase transition characteristics determine the reinforcement effect of the weak, so can’t use tempering heat treatment, such as improving the mechanical strength of pure titanium. The only heat treatment for industrial pure titanium is annealing.
Its main annealing method has three kinds: 1 recrystallization annealing 2 destress annealing 3 vacuum annealing. The first two aims to eliminate stress and process hardening effect to restore plasticity and forming ability.

Industrial pure titanium has great effect on processing hardness during material production. By different cold working, TA2 yield strength increases, therefore in the process of titanium production, after cold and hot working, plastic, in order to restore a stable organization of fine grain and uniform mechanical properties, should carry on the recrystallization annealing. The recrystallization temperature of pure titanium is 550-650 ℃, thus the recrystallization annealing temperature should be higher than the recrystallization temperature, but less than alpha beta phase transition temperature. In 650-700 ℃ annealing can obtain the highest comprehensive mechanical properties (due to higher than 700 ℃ annealing will cause coarse grains, led to the decrease of the mechanical properties). The cold work hardening of annealing material can be eliminated by annealing in 10-20 minutes. This heat treatment is generally carried out in titanium production units. In order to reduce the gas pollution of heat treatment and remove the hydrogen absorbed by the titanium in the process of heat treatment, the current products of titanium materials are required for annealing treatment under vacuum atmosphere.

In order to eliminate the residual stress of titanium in the process of processing (such as welding, explosive recombination, slight cold deformation in the manufacturing process), the stress treatment should be carried out. The stress annealing generally does not need to be carried out in a vacuum or argon atmosphere, as long as the atmosphere inside the furnace is micro-oxidizing.