Shape Memory Alloy β€” Superelasticity & Phase Transformation

Interactively explore austenite ↔ martensite transitions, superelastic hysteresis, and thermal shape recovery in smart materials like Nitinol.

Phase: Austenite Cubic structure β€” high stiffness, shape-restoring
Crystal Lattice
Stress-Strain Curve
50
Temp (Β°C)
0.0
Stress (MPa)
0.00
Strain (%)
100%
Austenite fraction
75
Stiffness (GPa)
Presets:
Nitinol (NiTi) β€” the most widely used SMA. Transformation temperatures: Ms=βˆ’10Β°C, Mf=βˆ’30Β°C, As=10Β°C, Af=40Β°C. Superelastic plateau ~500 MPa with ~8% recoverable strain. Used in medical stents, orthodontic wires, and robotic actuators.
About Shape Memory Alloys

Shape memory alloys (SMAs) exploit a reversible solid-to-solid phase transformation between a high-symmetry austenite phase and a lower-symmetry martensite phase.

Shape Memory Effect: Cooling into martensite, deforming, then heating above Af recovers the original shape. The austenite phase is the "remembered" configuration.

Superelasticity: At T > Af, applied stress can induce martensite. Upon unloading the alloy transforms back to austenite recovering up to ~8% strain β€” a "rubber-like" metal.

Transformation temperatures (Nitinol): Martensite start Ms, martensite finish Mf, austenite start As, austenite finish Af. These are tunable by composition (Ni:Ti ratio).

Applications: Cardiovascular stents, guidewires, orthodontic archwires, actuators, vibration dampers, aerospace morphing structures.