Shenzhen Wuge Industrial Co., Ltd

The annealing temperature of Nitinol (NiTi) alloy depends on the specific application goals (such as shape memory effect, superelasticity, or adjustment of mechanical properties), usually ranging from 400 ° C to 600 ° C. The following are key annealing parameters and precautions:

1. Annealing temperature range

Shape memory effect optimization:

400 ° C-500 ° C: Suitable for adjusting the phase transition temperature (such as martensitic → austenitic transformation) to restore the alloy to its predetermined shape at a specific temperature.

Super elastic treatment:

450 ° C-550 ° C: Improve superelasticity performance, suitable for medical devices such as vascular stents.

Eliminating processing stress:

300 ° C-400 ° C: Low temperature annealing can reduce residual stress after cold working, but may not completely eliminate it.

The annealing temperature of nickel titanium alloy tubes aims to eliminate residual stresses generated during processing, stabilize their size and properties, and improve the toughness of the material. For example, annealing nickel titanium alloy tubes after cold drawing in this temperature range can effectively relieve internal stress and prevent deformation or cracking caused by stress release during subsequent use.

2. Time and cooling method

Time: Usually 10-60 minutes, prolonged time may lead to grain coarsening or oxidation.

Cooling method:

Air cooling: applicable in most cases.

Water quenching: Rapid cooling can fix high-temperature phases (austenite), but may introduce residual stresses.

3. Key influencing factors

Composition: Nickel content (such as 50.8 at.% Ni) significantly affects the phase transition temperature and needs to be calibrated by differential scanning calorimetry (DSC).

Processing history: Materials after cold rolling or drawing may require lower temperature annealing to avoid recrystallization.

Protective atmosphere: It is recommended to anneal in argon or vacuum to prevent surface oxidation (TiO ₂ is easily formed at high temperatures).

4. Precautions

Avoid overheating: 600 ° C may cause excessive grain growth or precipitation of Ni ₄ Ti Ⅲ, which can damage the performance.

Test validation: It is recommended to determine the optimal process through DSC and mechanical testing.

The actual annealing temperature needs to be accurately determined based on the specific composition, processing technology, and requirements for the final performance of the alloy tube. For example, when the titanium content in the alloy is high, it may be necessary to adjust the annealing temperature appropriately; For nickel titanium alloy tubes that have undergone complex cold working processes, multiple tests may be required within the above temperature range to find the most suitable annealing temperature and ensure that the alloy tube achieves ideal comprehensive performance.