Description

Nitinol is a shape-memory metal: you can stretch it, bend it, squash it, twist it… but heat it up, and it springs right back to its original shape. This image shows the microstructure – the tiny shifts of crystal atoms that remember their old shape, ready to jump right back into position.

The map shown here was captured in a scanning electron microscope using a technique called digital image correlation, or DIC. DIC measures how materials deform under mechanical forces. Each of the roughly 23-million pixels in this image measures shear strain, which is a change in shape, over a 400-nanometer area. The layered microstructure made up of alternating positive (blue) and negative (orange) shear bands is how nitinol remembers its original shape.