What term is used for a material that returns to its original shape when reheated?

The term used for a material that returns to its original shape when reheated is known as a Shape Memory Alloy. These alloys are unique in that they can undergo a phase transformation at specific temperatures, which allows them to remember a particular shape. When deformed at a lower temperature, they can return to this 'remembered' shape upon being heated above their transition temperature. This phenomenon is due to the material's ability to change its crystalline structure, which effectively 'remembers' its original form.

The other material types listed do not possess this specific property. Metallic glasses refer to a class of metals with a non-crystalline structure that provide different mechanical properties. Elastomers are polymers known for their elasticity and flexibility but do not have a defined "memory" shape like Shape Memory Alloys. Composite materials consist of two or more different materials combined to enhance their properties, but they don't inherently return to a specific shape when reheated either.