Heat Treatment of Titanium Alloy

Annealing, solution, and aging treatment are the common heat treatment techniques used on titanium alloys. All types of titanium alloys can benefit from annealing, primarily to achieve the highest mechanical qualities, reduce stress, increase fluidity, and stabilize the structure. Solution and aging treatment are the main means of strengthening titanium alloys.

1. Stress Relief Annealing

The annealing temperature of stress relief annealing is 100-250℃ lower than the recrystallization temperature. The goal is to prevent and minimize deformation, as well as to eliminate or reduce internal tension throughout the production process. The workpiece’s section size, the degree of stress relief needed, and the machining history all affect how long it takes.

2. Full Annealing (Recrystallization annealing)

The annealing temperature is close to the recrystallization temperature and β transition point, and recrystallization mainly occurs during the annealing process, and the temperature is higher than the recrystallization temperature of the alloy. The purpose is to reduce the hardness, increase the plasticity, stabilize the structure and improve the processing performance. Different annealing techniques, temperatures, and cooling methods are used for different kinds of titanium alloys.

Machined parts

3. Double Annealing

Including high temperature and low temperature annealing, air cooling after annealing; The high temperature is 20-160 ℃ below the β transition point, and the low temperature is 300-500℃ below the phase transition point. The aim is to improve the ductility, fracture toughness and stable structure of the alloy.

4. Isothermal Annealing

A special form of double annealing, first heated to 20-160 ° C below the β transition point, after heat preservation, transfer to a low temperature furnace (600-650° C) heat preservation, and then air cooling to room temperature.

It is suitable for titanium alloys with high content of β-stable elements, using slow cooling to fully decompose the β-phase. The goal is to stabilize the organization.

5. Solution Heat Treatment

β transition point below 28–83 °C heating, and α+β two-phase zone transition temperature above. In certain circumstances, heating over the β transition point and quenching is also an option. The goal is to achieve a high proportion of aging enhancement in the metastable β phase.

6. Aging Treatment

It is typically heated to a temperature of 425 to 650 °C. The aging hardening curve can be used to calculate the aging temperature and aging duration. The aim is to enhance the alloy strength by encouraging the breakdown or precipitation of the metastable β phase.

 

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