 This mechanism has been recognized in many minerals (including quartz, calcite, olivine, pyroxenes, micas, feldspars, halite, garnets and zircons) and in metals (various magnesium, aluminium and nickel alloys).In metals and minerals, grains are ordered structures in different crystal orientations.Subgrains are defined as grains that are oriented at a  One mechanism could be the migration and agglomeration of like-sign dislocations in the LAGB, followed by grain boundary shearing.