Final answer:
Plastically deforming two previously undeformed specimens of the same metal involves plastic deformation, which is a permanent change in shape and size of a material when subjected to stress beyond its elastic limit.
Step-by-step explanation:
When plastically deforming two previously undeformed specimens of the same metal, the process involved is plastic deformation. Plastic deformation is a permanent change in shape and size of a material when subjected to stress beyond its elastic limit. In the case of metals, plastic deformation occurs when stress is gradually increased, causing the material to undergo irreversible deformation.