What temperature is needed to activate a Nitinol spring?
The memory effect of Shape memory nitinol spring stems from the change of crystal structure inside them.
Nitinol is a shape memory alloy. At lower temperatures, the internal crystal structure of the alloy is martensitic phase, which is relatively soft and easy to deform. When the nickel-titanium spring is deformed, it can maintain this deformed shape.
When the temperature is raised to a certain degree (phase transition temperature), the crystal structure of the alloy will be transformed into an austenite phase. The more regular structure of the austenitic phase will encourage the spring to return to its original memory shape, which produces a memory effect.