If a deformed material recovers its original shape after stress is reduced, the behavior is

The behavior is "elastic".

In physics, elasticity is the capacity of a body to oppose an impact and to come back to its real size and shape when that impact or power is evacuated. Solid articles will bend when sufficient powers are put on them. In the event that the material is elastic, the thing will come back to its original shape and size when these powers are lifted.