(1) A spring-shaped shape memory alloy after shape-setting (training) treatment

(2) At room temperature (below the martensitic transformation temperature), applying a load changes the shape.

(3) Shape after sufficient deformation, with the load removed

(4) When heated above the reverse transformation temperature, it begins to return to the memorized shape. (1/3 recovery)

(5) Continue heating. (2/3 recovery)

(6) Continue heating. (Full recovery to the original shape)

(1) Even immediately after heating (above the reverse transformation temperature), applying a load causes deformation due to stress-induced martensitic transformation.

(2) Because the temperature is above the reverse transformation temperature, simply unloading triggers reverse transformation back to the parent phase, and the shape returns to the original.