irreversible transition
A transition that changes the state of a system which cannot be readily reversed to restore the system to its original state. Example: The conversion of TiO2 (anatase) to TiO2 (rutile).
PAC, 1994, 66, 577. (Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)) on page 584 [Terms] [Paper]