Several common heat treatment methods for titanium alloys

Common heat treatment methods for titanium alloys are annealing, solution treatment and aging treatment. Annealing is applicable to all types of titanium alloys, mainly to obtain the best mechanical properties, eliminate stress, improve plasticity and stabilize the structure. Solution treatment and aging treatment are the main means of strengthening titanium alloys.

1. Stress relief annealing:

The annealing temperature is 100-250℃ lower than the recrystallization temperature;

The purpose is to eliminate or reduce the internal stress that occurs during processing and prevent and reduce deformation. The time required depends on the cross-sectional size of the workpiece, the processing history and the degree of stress elimination required.

2. Full annealing (recrystallization annealing):

The annealing temperature is close to the recrystallization temperature and the β transformation point. The annealing process mainly undergoes recrystallization, and the temperature is higher than the recrystallization temperature of the alloy.

The purpose is to reduce hardness, increase plasticity, stabilize the structure, and improve processing performance. For different types of titanium alloys, the type, temperature, and cooling method of annealing are different.

3. Double annealing

It includes two annealing processes, high temperature and low temperature, followed by air cooling; the high temperature is 20-160℃ below the β transformation point, and the low temperature is 300-500℃ below the phase transformation point.

The purpose is to improve the plasticity, fracture toughness and stable structure of the alloy.

4. Isothermal annealing

A special form of double annealing, first heated to 20-160℃ below the β transformation point, then transferred to a low temperature furnace (600-650℃) for insulation, and then air-cooled to room temperature.

Suitable for titanium alloys with high β stabilizing element content, slow cooling is used to fully decompose the β phase.

The purpose is to obtain a stable structure.

5. Solution treatment

Heat above the α+β two-phase transition temperature and below the β transition point at 28-83°C. In special cases, heat above the β transition point and then quench.

The purpose is to obtain a high proportion of metastable β phase with aging strengthening.

6. Timeliness treatment

Generally, heating is performed between 425-650℃. The aging temperature and aging time can be determined according to the aging hardening curve; the purpose is to promote the decomposition or precipitation of the metastable β phase, thereby improving the strength of the alloy.