Thermally induced recovery of the shape of a spring

This lecture demonstration package (LDP) concerns the reversible shape memory effect, which is exhibited by certain alloys. The demonstration simply consists of (plastically) deforming a spring-shaped specimen into an arbitrary shape and then using a hair-dryer to heat it up sufficiently to stimulate phase transformations within it in such a way as to cause the shape to revert to that of the spring. This only takes about 30 seconds. Of course, this is an effect that does require some explanation, even if it is a rather simplified one: the complete presentation proposed here, which includes an illustration of the changes in crystal structure involved, takes about three and a half minutes.

• Introduction
• Shape changes arising from dislocation glide and deformation twinning (a shear transformation)
• Sequence of microstructural changes during the shape memory effect
• IT resources - crystallography of the phase transformations in the Ni-50Ti alloy
• Equipment and facilities needed for the demonstration
• Video of the demonstration

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First created: August 2012. Resources converted to HTML5: April 2022.