When a heavy weight is suspended from a metal wire and then removed,the wire does not regain its original length. Why?

(N/A) When a metal wire is subjected to a deforming force within its elastic limit,it regains its original dimensions upon the removal of the force. However,if the deforming force exceeds the elastic limit,the material undergoes permanent deformation (plastic deformation). In this state,the internal restoring forces are insufficient to return the atoms to their original equilibrium positions,causing the wire to retain a permanent set or elongation.