Memory metal alloys have a rather remarkable property: they remember their shape. This “smart” property is the result of the substance’s ability to undergo a phase change – a kind of atomic ballet in which atoms in the solid subtly shift their positions in response to a stimulus like a change in temperature or application of mechanical stress. In this activity, visitors are invited to bend samples of NiTi memory metal into shapes of their choosing, and the samples return to their original shape when heat is applied. This behavior is discussed in terms of the metal’s austenite and martensite phases.
Full Instructions
Materials
- NiTi wire samples (low-temperature martensite phase approximately 3” long x 0.03” diameter)
- Source of heat (hot water or a hair dryer)
- Overhead projector with (a) tape and hair dryer or (b) clear dish of hot water (optional)