It is a common experimental observation that there is an inverse relationship between the median grain size in a deforming polycrystal and the applied deviatoric stress. This occurs because there is a balance between those processes leading to an increase in grain size, such as grain boundary migration, and those processes leading to a reduction in grain size, such as rotation recrystallisation. In reality using this relationship can be quite difficult, since metadynamic processes such as grain growth can affect the observed grain size, and even if it appears that no such modification has taken place, we have to be able to demonstrate that the observed grain size was formed during steady-state flow. The grain growth can be static, dtnamic or metadynamic. The growth can be Normal at high temperature when the boundaries are mobile or Pinned when other minerals pin onto the previous ones like micas inning onto quartz or feldspar grains. Grain growth can also be of porphyroblasts or subgrains.

Jessel et al. Monash Au